Comments on Policy & Economic Preliminary Assessment and Study Updates

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

No comments at this time.

2. Please provide your organization’s comments on the MIC Expansion Requests

The MIC Expansion Request process, while an improvement to MIC functionality from the past, has not provided sufficient, meaningful changes to the MIC process overall. We encourage CAISO to work with stakeholders in other initiatives to address remaining problems with the current MIC process and to develop more effective enhancements.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

In the preliminary results shared during the meeting, CAISO identified multiple constraints in the East of Pisgah area and indicated it is evaluating several potential solutions, including the construction of new transmission lines. Given the recurring and significant nature of the constraints in this area, as well as the substantial resource build that the CPUC portfolios anticipate in this region, ACP-California supports CAISO moving forward with a wire-based solution that will enable resource development in both the medium and long term.

Because large new transmission lines have recently faced delays in reaching commercialization, it is prudent for CAISO to advance approval of a proposed solution for this area as quickly as possible. ACP-California therefore supports approval of a wires-based solution in the 2025-26 TPP.

ACP-California looks forward to CAISO’s proposed solutions in the Draft Transmission Plan.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

No comments at this time. But ACP-California looks forward to CAISO’s proposed solutions in the Draft Transmission Plan. 

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

No comments at this time. 

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

We note CAISO's findings regarding solar driven constraints in the Greater Fresno area and encourage the CAISO's attention to solutions in this region given the importance of this solar development region. ACP-California looks forward to CAISO’s proposed solutions in the Draft Transmission Plan.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

The preliminary results of CAISO’s economic analysis show significant congestion on Path 15 and Path 26. While both paths have experienced notable congestion for years, the 2025-26 preliminary analysis reflects sharp increases – even compared to last year’s results. For example, in the 2024-25 Final Transmission Plan, Path 15 showed approximately $390 million in congestion costs in 2034. In contrast, the preliminary results shared during the November 2025 meeting show more than $1.2 billion in congestion costs on Path 15 in 2035, which is over three times last year’s value.

For Path 26, the 2024-25 Final Transmission Plan reported $241 million in congestion costs, whereas the November 2025 preliminary results show $350 million in 2035 – an increase of nearly 50% year over year. These congestion costs are substantial and, if accurate, clearly justify transmission expansion to mitigate congestion, particularly on Path 15.

ACP-California strongly supports CAISO moving forward with evaluating and proposing transmission expansion that can provide significant benefits by reducing congestion costs across these paths. If the Transmission Economic Assessment Methodology (TEAM) fails to find that a proposed solution is economic, we recommend a thorough evaluation of whether TEAM remains an appropriate methodology for assessing the economic benefits of transmission options. Congestion costs reaching into the billions of dollars per year should plainly warrant some form of transmission expansion. If the current methodology is not producing outcomes that support necessary and economically beneficial transmission upgrades, we urge CAISO to examine why that is the case and consider adjustments or alternative approaches that will allow cost-effective transmission benefiting California ratepayers to be approved.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

ACP-California appreciates CAISO’s work on reviewing different approaches to better capture congestion revenue allocation as changes are made to the CAISO markets and congestion revenue allocation across it. We support ongoing discussion and consideration of the options to appropriately capture congestion revenue as EDAM becomes operational and as additional changes to the congestion revenue allocation design are considered.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

No comments at this time. 

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

The Bay Area Municipal Transmission group (BAMx)^[1] appreciates the opportunity to comment on the CAISO’s 2025-26 Transmission Planning Process (TPP). The comments and questions below address the material presented at the CAISO Stakeholder meeting on November 19, 2025.

BAMx thanks the CAISO for its responsiveness in addressing its questions regarding the scope of the Oro Loma 70 kV Area Reinforcement Project (Re-scope)(Greater Fresno Area)[2] that the CAISO management plans to approve in this TPP cycle. BAMx is satisfied with the CAISO staff’s response regarding the consistency of the project scope with the one submitted by PG&E in its Request Window application.[3]

[1] BAMx consists of City of Palo Alto Utilities and City of Santa Clara, Silicon Valley Power.

[2] CAISO’s November 19^th Presentation, slide 16.

[3] PG&E’s 2025 Request Window Proposals, CAISO 2025-2026 Transmission Planning Process, September 25, 2025, pp.9-12.

2. Please provide your organization’s comments on the MIC Expansion Requests

 No comments at this time.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

Need Additional Clarity Regarding Adjustments Made to the CPUC-Provided Portfolios

During the November 19^th presentation, the CAISO included tables for different SCE study or Maximum Import Capability (MIC) areas to show the adjustments made to the CPUC-provided portfolios.[1] These adjustments fall into the following three categories.

1. Unaccounted TPD Mapped Resources: BAMx understands that the term "Unaccounted TPD" in the context of the CAISO TPP refers to Transmission Plan Deliverability (TPD) that has been allocated to a specific set of generation projects but is not yet reflected or "accounted for" in the resources that the CPUC uses in its long-term resource portfolios. The challenge is that the queue of interconnection requests and the allocated TPD can change more quickly or differ from the specific resources modeled in the CPUC's Integrated Resource Plan (IRP).
2. Additional In-Development Resources: These are the Additional in-development resources modeled by PTO based on project status; and
3. Non-CPUC Resources: Per the data submittal from non-CPUC jurisdictional entities by January 15, 2025, these non-CPUC resources were evaluated in this TPP.

Table 1 below provides a summary comparison of the FCDS resources (MW) assumed in the CPUC’s original versus the adjusted portfolios in the 2035 Base case. Most of the difference is attributed to 4-hour BESS assumptions. It shows that the Adjusted portfolio assumes nearly 11,209MW of 4-hour BESS than the one assumed in the original CPUC portfolio in 2035.

Table 1: A Comparison of FCDS Resources Assumed in Original vs. Adjusted Portfolio in the 2035 Base, By Resource Type

*Source: 2025-2026 Transmission Planning Process, Stakeholder Meeting, February 26, 2025, p.65

** Source: Policy-driven Deliverability Assessment Preliminary Results Transmission Infrastructure Planning, 2025-2026 Transmission Planning Process Stakeholder Meeting, November 19, 2025, p.30

BAMx noticed that the level of unaccounted TPD Mapped Resources in the SCE MIC areas/regions in the current TPP has gone up substantially relative to the last TPP. For example, it was 3,360MW in the 2034 Base portfolio in the 2024-2025 TPP, whereas it has almost doubled to 7,323MW in the 2035 Base portfolio in the 2025-2026 TPP. In particular, the unaccounted TPD Mapped Resources in the Eastern area add up to 4,451MW in the 2035 Base portfolio, whereas this amount was limited to 1,090MW in the 2034 Base portfolio in the 2024-2025 TPP. There is a need to closely scrutinize these amounts as a significant amount of undeliverable baseline and portfolio resources in several SCE regions are attributed to the generic 4-hour BESS resources that the CAISO has modeled as a proxy for the unaccounted TPD Mapped Resources.

BAMx also observes that the adjustments made to the original portfolio cannot be fully explained by a combination of Unaccounted TPD Mapped Resources, Additional In-Development Resources, and Non-CPUC Resources. In Table 2 below, we compare the 4-hour BESS resources assumed in the original versus the adjusted Portfolio in the 2035 Base portfolio. In the Eastern SCE area, CAISO has modeled 7,891MW of 4-hr BESS, an increase of 3,906MW in FCDS resource capacity from the one included in the Original CPUC portfolio in 2035. The Unaccounted TPD Mapped Resources is 4,454MW, which is higher than the difference of 3,906MW. On the contrary, the difference in the East of Pisgah area of 2,661MW can be fully explained by the Unaccounted TPD Mapped Resources. It is not clear what role the 90MW of non-CPUC resources play. Shouldn’t they be part of the 3,871MW of 4-hr BESS modeled in the 2035 case to ensure that there is not double-counting of resources modeled in the original CPUC portfolios and Non-CPUC IRP resources? Also, SCE Northern Area, Metro Study Area, and North of Lugo Study Area do not have any Unaccounted TPD Mapped Resources. Still, the additional in-development and non-CPUC resources do not fully account for the difference between the original and adjusted portfolios in these areas.

Table 2: A Comparison of 4hr-BESS Assumed in Original vs. Adjusted Portfolio in 2035 Base, By CAISO Study Area

Given the significant role these additional 4-hour BESS resources play in increasing the undeliverable baseline and portfolio resources across several SCE regions, it is critical that the CAISO provide precise accounting of these resources to stakeholders. Without this transparency, stakeholders won't be able to provide meaningful feedback on the need and scope for mitigation(s) triggered by several deliverability constraints in the SCE study/MIC regions, as we discuss below.

SCE Northern Interconnection Area

Below, we include BAMx’s suggestions and recommendations for each deliverability constraint in the SCE Northern Interconnection Area for the CAISO’s consideration.

Windhub Area Constraint[2]:

Please describe the incremental deliverability added by the potential mitigations to address the Windhub Area Constraint. Without this information, stakeholders cannot evaluate whether these mitigations are adequate or appropriate given their costs, which are also unknown at this time.

1. 1. Windhub – PG&E Substation 500 kV line
   2. Windhub – Whirlwind 500 kV line[3]

BAMx supports the CAISO’s proposed plan to relocate some of the resources behind the Windhub area constraint, including the 203 MW of generic resources at Windhub substation, to avoid any unnecessary major transmission upgrade.

Midway–Whirlwind 500 kV line Constraint[4]:

The CAISO has proposed the following potential mitigation options to address the undeliverable baseline and portfolio resources behind this constraint.

1. 1. Reconductor PG&E segment of Midway – Whirlwind with advanced conductor (TBD)
   2. Windhub – PG&E Substation 500 kV line (TBD)
   3. PTEP ($2.42B)
   4. K-SEL ($2-4B)

Please describe the incremental improvement in deliverability these potential mitigations would provide. Also, please explain why the following two no-cost options identified in the previous TPP are not appropriate/adequate in addressing this deliverability constraint. The CAISO needs to fully evaluate these two options before considering any major transmission upgrade.

1. 5. Bypass the series capacitor of the Midway–Whirlwind 500 kV line (No cost)
   6. Uprate Midway – Whirlwind 500 kV line (PGE segment normal rating) (No cost)

SCE Metro Constraints[5]

BAMx notes that due to the significant increase in BESS resources within the area, the previously proposed Del Amo 500kV facilities, considered in the 2022–2023 TPP policy study, are no longer needed as a policy-driven transmission upgrade. BAMx supports CAISO’s assessment and looks forward to its comprehensive economic, policy, and reliability benefit analysis to confirm that these upgrades are not needed to address the identified secondary system need deliverability constraint.

SCE North of Lugo (NOL) Interconnection Area

Control Transformer Constraint: BAMx cannot weigh in on this constraint as the CAISO has not completed its evaluation yet. Once these mitigation options have been identified, BAMx urges CAISO to provide detailed results, including the preferred mitigation projects and the other alternatives considered as part of the Draft Transmission Plan.

Calcite-Lugo 230kV Line constraint: BAMx recommends that the CAISO evaluate no-cost alternatives of expanding the planned Calcite CRAS or relocating generic battery storage (especially since the large amount of adjustments to the 4-hour BESS is driving the undeliverable amounts behind this constraint) before exploring options, such as Reconductor Lugo – Calcite with advanced conductor, the cost of which is still unknown.

SCE Eastern Interconnection Area

Serrano-Alberhill-Valley 500 kV No.1[6]: The CAISO’s evaluation indicates that West of Colorado River CRAS cannot be expanded to monitor overloads on Devers transformers. Furthermore, reducing the generic battery storage behind this constraint may not be adequate. BAMx requests that the CAISO fully explore the battery storage adjustments and their effectiveness. If this additional assessment determines it to be inadequate, BAMx would support a transmission upgrade entailing a new Devers No. 3 transformer over more expensive mitigations, such as the New Devers-Mira Loma 500 kV transmission line ($1.1B) and New Devers-Red Bluff 500 kV transmission line ($875M) identified for last year’s TPP.

East of Pisgah Interconnection Area[7]

As shown in Table 3 below, the Trout Canyon-Lugo 500kV line is the only project that effectively addresses all four (4) deliverability constraints within the East of Pisgah (EOP) Interconnection Area. However, given the high capital cost of $2 billion associated with it, the CAISO needs to consider a combination of different projects that would address these deliverability constraints at a lower cost. For example, a combination of the Marketplace-Adelanto AC-DC conversion, the Sloan Canyon-Marketplace 500kV line, and the Sagebrush Interconnection may be more cost-effective than approving the Trout Canyon-Lugo 500kV line. However, as we discussed earlier, it is critical to assess the incremental deliverability of these alternative mitigation options to make that determination.

Table 3: Potential Mitigations Considered for Deliverability Constraints Identified in the East of Pisgah Interconnection Area

Furthermore, one of the key assumptions that is driving the deliverability constraints in the EOP area is the assumed 3,000MW of Wyoming wind and 1,100MW of Idaho wind connected to Eldorado and Harry Allen, respectively. The CAISO needs to consider the uncertainty associated with these wind resources and follow the CPUC’s directive to the CAISO to defer triggering transmission for additional amounts of resources in the 2025-2026 base portfolio, that transmission upgrades already approved or in development do not already accommodate.

[1] CAISO’s November 19^th Presentation, pp.31-36

[2] CAISO’s November 19^th Presentation, p.45

[3] We know that We know that Windhub – Whirlwind 500 kV line will approximately add 2,500MW of additional deliverability based on the prior CAISO transmission capability estimates.

[4] CAISO’s November 19^th Presentation, p.47

[5] CAISO’s November 19^th Presentation, p.68

[6] CAISO’s November 19^th Presentation, p.95

[7] CAISO’s November 19^th Presentation, p.132

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

See the comments in response to Q.3 above.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

 No comments at this time.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

BAMx notes that the information on deliverability constraints for the North of Greater Bay Area (NGBA) and the Greater Bay Area (GBA) is meagre and incomplete relative to that included in the SCE and SDG&E areas assessment. For example, NGBA and GBA assessment do not provide any of the following relevant information for stakeholders to meaningfully assess the CAISO’s preliminary findings.

1. Portfolio resources behind the constraint (Installed FCDS capacity);
2. Generic portfolio battery storage behind the constraint (Installed FCDS capacity);
3. Deliverable portfolio resources w/o mitigation (Installed FCDS capacity);
4. Total undeliverable baseline and portfolio resources (Installed FCDS capacity); and
5. Scope and costs associated with any Mitigation Options.

BAMx notes that the deliverability constraints observed in the NGBA, GBA, Fresno, and Kern areas have almost all mitigations listed as TBD. Once these mitigation options have been identified, BAMx urges CAISO to provide detailed results including the preferred mitigation projects and alternatives considered as part of the Draft Transmission Plan.

Co-optimization of Reliability and Policy

BAMx also notes that almost all the deliverability constraints observed in the GBA were also observed in the CAISO reliability assessment. BAMx encourages the CAISO staff to perform a comprehensive assessment that takes into consideration the degree to which the selected mitigation solution mitigates the reliability constraint and facilitates the deliverability of renewable resources required by policy. Presumably, the selected project's cost will be compared to feasible alternatives (both transmission and non-transmission) that can achieve the same results. One good example is the one BAMx suggested in its comments on the CAISO’s reliability assessment for the Eastshore and Newark area, where a regional planning effort may require the CAISO to consider approving a transmission project that enhances imports into the GBA, rather than pursuing piecemeal reconductoring multiple 230 kV lines with high-ampacity conductors, which may involve tower replacements, construction and clearing issues. This is especially relevant as CAISO is reviewing the validity of load growth in this area.[1]

[1] See BAMx comments in the CAISO’s 2025-2026 Transmission Planning Process, dated October 9, 2025, in response to Q.3.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

In the 2024-2025 Board Approved Transmission Plan the Path 15 Corridor[1] 2034 and 2039 Base portfolio PCM results showed congestion of $389.42M and $521.8M. The congestion results CAISO provided in the November 19^th presentation[2] show that the congestion in the 2035 and 2040 Base portfolio have significantly increased on the Path 15 Corridor to $1,242.81M and $1,320.12M. BAMx observes that in comparing the 2034 PCM and 2035 PCM congestion results show an over 200% increase in total congestion cost across the Path 15 Corridor. It is not clear what the driver is behind this 200% increase in one year of PCM modeling, and BAMx asks CAISO to investigate and report back on the congestion drivers contributing to the 200% increase in congestion on the Path 15 Corridor. Knowing the drivers of congestion could be a valuable feedback point to the CPUC for developing the 2026-2027 TPP portfolios.

[1] CAISO 2024-2025 Transmission Plan, Board Approved, May 30, 2025, p. 139

[2] CAISO’s November 19^th Presentation, p.198 & p.203

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

In the current TEAM-based economic assessment, congestion revenue is allocated to transmission owners. The CAISO is considering a potential revision of congestion revenue allocation based on flow contribution (Flow-Based Revisions, hereafter). Allocation will be based on the net generation distribution factors (GDFs) for the area, applied to specific constraints.

Downsides of the CAISO-Proposed Potential Flow-Based Revisions 

BAMx has the following concerns about allocating congestion revenue to areas with a net positive impact on transmission constraints.

Complexity & Transparency

The long-term planning studies for TEAM projects (which look 10+ years out) inherently rely on highly complex Production Cost Models (PCMs) that simulate thousands of hours of dispatch. A flow-contribution method relies on Net Generation Distribution Factors (a proxy for flows). These factors can be volatile and are sensitive to the full network model (FNM) assumptions, including assumed resource locations and future outages. Basing a 20- to 50-year NPV calculation on a flow-based allocation mechanism requires predicting how flows will contribute to future congestion revenue, which significantly increases the modeling risk and uncertainty of the benefit-cost ratio. This violates the TEAM principle of providing a streamlined, predictable, and robust assessment. In other words, this potential revision adds computational complexity and may reduce transparency for stakeholders compared to the current TEAM method, which is simpler and tied to ownership rights.

Volatility & Uncertainty

Under the proposed potential revision, congestion revenues could become highly volatile, since flow contributions vary with system conditions, dispatch patterns, and topology changes. Transmission owners and market participants may face uncertain revenue streams, complicating investment planning and financial forecasting.

Misalignment with Cost Responsibility

Transmission owners invest in infrastructure and expect compensation tied to their assets. Flow-based allocation may decouple revenues from ownership, potentially discouraging future transmission investment if owners perceive reduced or unpredictable returns.

Regional Equity Concerns

The CAISO-proposed revised approach can be applied to congestion within the CAISO or the entire WECC system. BAMx understands that areas with large net-positive flow impacts may receive disproportionate allocations, while others may see reduced benefits despite contributing to system reliability. In the case of economic study requests or projects paid exclusively by CAISO ratepayers, BAMx does not have any regional equity concerns with allocating CAISO congestion revenues solely under the proposed approach. However, if the economic project costs are to be shared across multiple balancing authority areas, it would be advisable to allocate the congestion revenues WECC-wide. In other words, the decision to apply to congestions within the CAISO or the entire WECC system would depend on the cost responsibility of the proposed economic project.

Upsides of the CAISO-Proposed Potential Flow-Based Revisions

The potential upsides of the CAISO-proposed potential revisions include

Investment Incentives

Areas consistently showing positive flow contributions may be motivated to invest in generation or transmission that enhances those benefits.

Transparency of Grid Impacts

By tying revenues to GDFs, stakeholders gain clearer visibility into how their operations affect constraints.

Fairness & Usage Alignment

Revenues go to areas that actually contribute to relieving or causing congestion, rather than simply to transmission owners by default.

Efficiency Signals

Provides locational price signals that encourage generation and load siting decisions aligned with grid efficiency.

Overall Assessment

The ownership-based current TEAM approach is predictable and straightforward. Any deviation from it, based on perceived efficiency-oriented benefits of the flow-based approach, needs to be weighed thoroughly through additional assessment and stakeholder review.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

One of the key inputs to the resource optimization model and the bus bar mapping process is transmission capability information supplied by the CAISO.[1] BAMx’s review of the deliverable full capacity deliverability status (“FCDS”) portfolio resources without mitigation, that is, on the existing transmission behind several deliverability constraints identified in the CAISO November 19^th presentation, indicates that those amounts differ considerably from those used to develop the draft 2026-2027 TPP portfolios. Some of the constraints identified by the CAISO 2025-2026 TPP policy assessment, such as the Whirlwind and Midway–Whirlwind 500 kV line constraints, are not even included in the transmission capability estimates underlying the draft 2026-2027 TPP portfolios. Furthermore, in the event of some deliverability constraints, the CAISO is considering different area delivery network upgrades (“ADNU”) than those included in earlier transmission capability estimates. Also, both the estimated costs (M$) and the FCDS capability, based on the on-peak study resource Output (MW), associated with some of these ADNUs have been significantly revised, as reported in CAISO’s November 19^th presentation.

In Table 4 below, we compare the transmission capability estimates used to develop the draft 2026-2027 TPP portfolios with CAISO’s latest 2025-2026 TPP assessment. BAMx recognized that this is not an apples-to-apples comparison, as the CAISO has made adjustments to the CPUC’s generic portfolio or unaccounted Transmission Plan Deliverability (“TPD”), where applicable, and has evaluated additional in-development resources modeled by PTO based on project status and non-CPUC resources in the 2025-2026 TPP, etc. Although the list of constraints in Table 4 is not comprehensive, it highlights the importance and urgency of incorporating updated CAISO data to improve the validity of the 2026-2027 TPP portfolios.

Table 4: A Comparison of Transmission Capability Estimates

*Source: TxCapabilityEstimates_2024 tab of the Compact Dashboard – Initial Mapping 26-27 TPP Base Case

** Source: 2025-2026 TPP Policy and Economic assessment and study updates stakeholder meeting, November 19, 2025, pp. 38-100

N/A: Not Available

Given the considerable differences and updates in the transmission capability estimates outlined in Table 4, BAMx strongly urges the CAISO to provide updated estimates to the CPUC staff so that they can update its proposed 2026-2027 TPP portfolios.[2]

[1] For this purpose, the CAISO develops transmission capability estimates that limit the amount and deliverability status of candidate resources that can be selected or mapped in transmission-constrained areas. The information includes previously identified conceptual transmission upgrades along with an estimate of the associated incremental increase in transmission capability.

[2] See California Public Utilities Commission’s (Commission) Administrative Law Judge’s Ruling Seeking Comments on Busbar Mapping of Electricity Resource Portfolios for 2026-2027 Transmission Planning Process (“TPP”), issued on November 3, 2025.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

The California Community Choice Association (CalCCA) appreciates the opportunity to comment on the California Independent System Operator’s (CAISO) 2025-2026 Transmission Planning Process (TPP) study updates and preliminary policy and economic assessments. CalCCA does not have any comments on the recommended reliability projects less than $50 million at this time.  

2. Please provide your organization’s comments on the MIC Expansion Requests

CalCCA appreciates the CAISO conducting the maximum import capability (MIC) expansion process to facilitate the contracting of imports necessary to support long-term policy needs. However, the MIC expansion process, and other elements of the MIC process,[1] may be insufficient to provide load serving entities (LSE) and developers the certainty necessary to move forward with long-term procurement activities that support the amount of imports projected in the California Public Utilities Commission (CPUC) portfolios.

While the ability for the CAISO to expand MIC is currently very dependent on the CPUC portfolios, actual investments in out-of-state resources and their development milestones should also inform upgrades needed to expand MIC. The primary challenge with the MIC expansion process is that, when the CAISO’s study of valid MIC expansion requests identifies limitations that prevent the expansion of MIC, deliverability upgrades to support the MIC expansion will not be triggered. This is true even when a MIC request demonstrates resource adequacy (RA) contracts or power purchase agreements (PPA) to support the request.[2] CalCCA understands that the transmission upgrades are driven by the CPUC’s portfolios, but the portfolios are developed based on assumptions about resource availability and cost that may evolve over time. The result may be that actual capacity procured differs from what was planned in prior portfolios. This capacity will likely be incorporated into future portfolios as LSEs include the capacity in their individual IRPs that feed into the CPUC portfolios. Contracted for projects are therefore likely more indicative of the need for upgrades than the portfolios themselves, and should inform MIC expansions and upgrades needed to support them.

When California LSEs demonstrate investments in out-of-state resources, it is prudent for the CAISO to study the upgrades necessary to make those projects deliverable so that capacity is not stranded. The process for expanding MIC through upgrades should account for both the local regulatory authorities’ (LRA) planning assumptions and actual investments and development milestones of contracted out-of-state resources.  This is conceptually similar to the way in which transmission development is conducted for resources interconnecting to the CAISO grid in which: (1) the TPP has the benefit of the CPUC portfolios; and (2) the Generator Interconnection Process reviews resource needs, available queued projects, and commercial interest to develop transmission needed for deliverability.

[1]            These comments focus on improvements to the MIC expansion process. CalCCA looks forward to working with the CAISO on other improvements to the overall MIC process in a future stakeholder initiative.

[2]            For example, Sunzia’s request includes 1,898.1 MW at PV West. The CAISO has indicated that this quantity exceeds the amount included in the 2025-2026 CPUC base portfolio. However, the 2026-2027 proposed limited-wind sensitivity includes existing transmission rights on Sunzia, plus an additional 2 GW (See CPUC, 26-27 Transmission Planning Process RESOLVE Modeling Results (Sept. 30, 2025) at slide 66: https://www.cpuc.ca.gov/-/media/cpuc-website/divisions/energy-division/documents/integrated-resource-plan-and-long-term-procurement-plan-irp-ltpp/2024-2026-irp-cycle-events-and-materials/assumptions-for-the-2026-2027-tpp/ruling_26-27-tpp-results_updated_20251013.pdf). MIC requests supported by RA contracts and/or PPAs and the likelihood of capacity that is already contracted for showing up in future portfolios should provide strong indicators of the need for upgrades to expand MIC.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

CalCCA has no comments on the preliminary policy assessment results for the SCE area at this time.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

CalCCA has no comments on the preliminary policy assessment results for the GLW area at this time.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

CalCCA has no comments on the preliminary policy assessment results for the SDG&E area at this time.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

CalCCA has no comments on the preliminary policy assessment results for the PG&E area at this time.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

CalCCA has no comments on the preliminary economic analysis at this time.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

CalCCA has no comments on the testing results of congestion revenue allocation.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

The CAISO proposes to reserve deliverability for geothermal, offshore wind, out-of-state wind, and non-battery long-duration energy storage resources in the quantities and locations included in the 2035 base portfolios. As CalCCA stated in the Interconnection Process Enhancements initiative, CalCCA agrees that a reservation process is necessary to allocate deliverability to long-lead time (LLT) resources that have longer project development cycles.[1]

Reservations of deliverability for LLT resources, however, limit the amount of deliverability available to allocate to other resources that may be commercially viable and contracted for to meet policy and reliability objectives. As described in section 2 above, the CPUC’s portfolios are developed using assumptions about technology availability and cost. To the extent these assumptions change, procured resources may differ from the portfolios. The CAISO should ensure that its process for releasing reserved TPD considers the LRAs’ planning assumptions and actual investments in new capacity and development milestones of contracted resources. This process should take place annually within the TPP to ensure reservations continue to reflect actual resource procurement and development.

[1]            See CalCCA Interconnection Process Enhancements Track 3 Straw Proposal Comments (Dec. 10, 2024): https://cal-cca.org/wp-content/uploads/2024/12/Comments-on-Interconnection-Process-Enhancements-Track-3-Straw-Proposal-12-02-04.pdf. (“CalCCA agrees with the CAISO that it will be necessary to allocate TPD to long-lead time (LLT) resources such as offshore wind, out-of-state wind, and geothermal that currently have longer project development cycles that may not be compatible with the updated TPD allocation process outlined in Section 2. The CAISO’s straw proposal for allowing eligible resources an extension to seek TPD allocations can efficiently and equitably meet this need with additional work to define the details around: (1) how much TPD can be reserved for this purpose; and (2) when TPD that is reserved for LLT resources would be released after a certain time if it goes unused.”)

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

The Public Advocates Office at the California Public Utilities Commission (Cal Advocates) provides these comments on the California Independent System Operator’s (CAISO) stakeholder meeting on the 2025-2026 Transmission Planning Process – Policy and Economic Assessment and Study Update on November 19, 2025.  Cal Advocates is an independent ratepayer advocate with a mandate to obtain the lowest possible rates for utility services, consistent with reliable and safe service levels and the state’s environmental goals.[1]

Cal Advocates has no comments on the recommended reliability projects with an estimated cost less than $50 million.

[1] Cal. Pub. Util. Code, § 309.5.

2. Please provide your organization’s comments on the MIC Expansion Requests

At the November 19, 2025 meeting, CAISO identified the Maximum Import Capacity (MIC) expansion requests that will trigger transmission upgrades but did not provide the costs for the triggered upgrades.[1]  For this reason, CAISO’s analysis for the MIC expansion requests is incomplete.  Cal Advocates recommends that CAISO provide the costs for any upgrades necessary to accommodate MIC expansion requests in CAISO’s draft final 2025-2026 Transmission Plan.

[1] 2025-2026 Transmission Planning Process – Policy & Economic Preliminary Assessment and Study Updates, CAISO, November 19, 2024 (CAISO November Presentation) at slide 23.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

The following are Cal Advocates comments on specific Southern California Edison Company (SCE) constraints and projects discussed at the November 19, 2025 meeting.

1. Midway – Whirlwind Constraint

CAISO’s resource deliverability results for the 2035 and 2040 On-Peak Midway – Whirlwind Constraint are inconsistent and require further discussion to explain their inconsistency.  Specifically, CAISO estimates that 1,268 megawatts (MW) of the base portfolio resources will be undeliverable in 2035 with the existing transmission capacity during on-peak hours on the Midway -Whirlwind Constraint but estimates only 646 MW of the base policy portfolio resources will be undeliverable in 2040 during on-peak hours on the Midway – Whirlwind Constraint.[1]  To ensure the portfolio resources are deliverable, CAISO proposes several expensive mitigation options, including reconductoring a section of the Midway-Whirlwind 500 kilovolt (kV) line and two other projects with costs greater than $2 billion. Cal Advocates does not support these options.[2]  During the presentation, CAISO staff agreed that reducing the 433 MW of energy storage behind the Midway – Whirlwind Constraint can assist with addressing the capacity issues on the Midway-Whirlwind Constraint in 2040 during on-peak hours.[3] Cal Advocates prefers this lower cost solution to address deliverability issues on the Midway-Whirlwind Constraint.  

Based on the November 19, 2025 presentation, remedial action schemes (RAS) are cost effective tools to address deliverability issues on several constraints including addressing an estimated 680 MW of potentially undeliverable resources at the Windhub #1 and #2 500/230 kV transformer constraint.[4]  Thus, in addition to reducing energy storage at the constraint, Cal Advocates recommends CAISO consider a RAS that would bypass the series capacitors on the Midway-Whirlwind 500 kV line to mitigate any remaining  capacity issues on the constraint.  Cal Advocates also recommends that CAISO provide an analysis on the effectiveness of the mentioned lower cost mitigations in the draft final 2025-2026 Transmission Plan.  This effectiveness analysis should explain whether 433 MW of energy storage can be relocated without triggering another transmission upgrade.  If CAISO determines that the proposed RAS would not work to address the potential deliverability issues, then CAISO should explain why the RAS would not work in the draft final 2025-2026 Transmission Plan.  

2. Del Amo 500 kV Facilities

At CAISO’s November 19, 2025 meeting, CAISO staff stated that the “Del Amo 500 kV facilities,” approved as a policy project in 2022, are no longer necessary due to an increase in energy storage in the project area.[5]  Cal Advocates recommends CAISO confirm that the “Del Amo 500 kV facilities” project is the Serrano-Del Amo Mesa 500 kV Transmission reinforcement project.  CAISO approved a Serrano-Del Amo Mesa 500 kV Transmission reinforcement project, which has four components, in the SCE service area in its 2022-2023 Transmission Plan to provide needed transmission capacity in the LA Basin. [6] Cal Advocates also recommends CAISO confirm whether it intends to cancel the entire scope of the Serrano-Del Amo Mesa 500 kV Transmission reinforcement project with an estimated cost of $1,125 million[7] in the draft final 2025-2026 Transmission Plan. 

3. Calcite Lugo 230 kV Constraint

Based on its resource deliverability analysis, CAISO anticipates that there may be 705 MW of undeliverable resources at the Calcite Lugo 230 kV Constraint in 2040 during on-peak hours.  To address this transmission capacity issue, CAISO is considering the planned Calcite Centralized RAS (CRAS) and relocating energy storage behind the constraint to integrate the remaining base portfolio resources as well as other more expensive wire mitigation options.[8] Cal Advocates supports the consideration of a RAS coupled with relocating energy storage to address the potential transmission capacity issue at the Calcite Lugo 230 kV constraint.  Based on CAISO’s estimates, there will be 422 MW of energy storage behind the constraint by 2040,[9]  thus relocating this energy storage could have a significant impact on deliverability at the constraint.  The remaining undeliverable MW could be addressed with a RAS or another operational solution as mentioned.  As a precedent for this lower cost solution, CAISO already intends to use the planned Calcite CRAS and to reduce energy storage behind the Calcite 230 kV constraint by 2 MW to address potential transmission capacity issues on the constraint anticipated in 2035 during on-peak hours.[10]  

4) Serrano Alberhill-Valley Constraint

CAISO’s analysis finds that there is the potential for 926 MW of base portfolio resources behind the Serrano Alberhill Valley Constraint to be undeliverable in 2040 during peak demand hours.[11] CAISO is considering a new Devers 500/230 kV transformer to address this transmission capacity issue.  However, CAISO estimates that by 2040 there will be 749 MW of energy storage behind the Serrano Alberhill-Valley Constraint.  Again, Cal Advocates recommends relocating the anticipated energy storage at the constraint to address any potential deliverability issues.[12]  Cal Advocates also recommends that CAISO provide the cost-effectiveness of all available options to increase transmission capacity on the Alberhill Valley Constraint, including reducing the anticipated energy storage behind the constraint and potential operational changes.  CAISO’s effectiveness analysis should explain whether 749 MW of energy storage can be relocated from the Serrano-Alberhill-Valley Constraint without triggering an additional transmission upgrade.  CAISO should provide the results of this effectiveness analysis in the draft final 2025-2026 Transmission Plan.

[1]  CAISO November Presentation at pp. 47 and 55.

[2] CAISO November Presentation at pp. 47 and 55.

[3] CAISO November Presentation at p. 55.

[4] CAISO November Presentation at p. 50.

[5] CAISO November Presentation at p. 68.

[6] CAISO Board Approved 2022-2023 Transmission Plan, May 19, 2023 at pp. 6 & 105.

[7] CAISO Board Approved 2022-2023 Transmission Plan, May 19, 2023 at p. 6.

[8] CAISO November Presentation at p. 78.

[9] CAISO November Presentation at p. 78.

[10] CAISO November Presentation at p. 76.

[11] CAISO November Presentation at p. 102.

[12] CAISO November Presentation at p. 102.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

Consider Lower Cost Alternatives to the Proposed New Trout Canyon Lugo 500 kV Line

CAISO is again considering a new Trout Canyon Lugo 500 kV line estimated at $2 billion in 2022 dollars to increase transmission capacity in the GridLiance West (GLW) service area.[1]  Specifically, CAISO is considering a new Trout Canyon Lugo 500 kV line to address anticipated overloads and undeliverable base portfolio MW at the East of Pisgah interconnection.  Developing a new Trout Canyon-Lugo 500 kV line requires establishing a new transmission corridor across the California desert, which is a riskier project than increasing the transmission capacity of existing transmission infrastructure.  New transmission line development is riskier because the permitting review is more extensive than for existing infrastructure upgrades and it could result in opposition to the project or reveal site conditions that require unforeseen and costly mitigations.  As a lower cost alternative, CAISO did identify three distinct projects that have a total cost of $1.353 billion.[2] These combined alternative projects are considerably less of a burden on ratepayers than the proposed $2 billion Trout Canyon Lugo 500 kV line project.  The three distinct projects are:

1. The Mead – Adelanto Project Upgrade (MAP Upgrade project). This project will convert the existing Mead – Adelanto line from High-Voltage Alternating Current operation (HVAC) to High-Voltage Direct Current (HVDC) operation.  This conversion is expected to increase the Mead - Adelanto line capacity from 1,291 megawatt (MW) to 3,500 MW.[3]   As a result, the MAP Upgrade project will provide increased transmission capacity between southern California and southern Nevada, and specifically along the Eldorado-Lugo corridor.  In 2022, the MAP Upgrade project cost estimate was $1.1 billion.[4] 
2. The Sagebrush Interconnection project. GLW requests CAISO consider this project in the 2025-2026 Transmission Planning Process (TPP).  CAISO is currently determining if this project could be a reliability alternative.  This project has an estimated cost of $204 million.[5]
3. The Sloan Canyon Market Place 500 kV line.  GLW requests CAISO consider this project in the 2025-2026 TPP.  CAISO is currently determining if this project could be a reliability alternative. This project has an estimated cost of $49 million.[6]

To confirm whether the above lower cost alternatives are preferred to the new Trout Canyon Lugo 500 kV line, Cal Advocates recommends CAISO provide a cost effectiveness analysis on the East of Pisgah interconnection mitigations options in its draft final 2025-2026 Transmission Plan.  Cal Advocates also recommends CAISO coordinate a discussion on its cost-effectiveness analysis findings at the scheduled Transmission Planning Process (TPP) stakeholder meeting on April 15, 2026 on the draft final 2025-2026 Transmission Plan.

Cal Advocates also supports CAISO’s proposed mitigation at the Sloan Canyon-El Dorado Constraint, which involves using 260 MW of energy storage behind the Constraint in charging mode.[7]  

[1] CAISO 2022-2023 Transmission Plan, May 18, 2023 at p. 3.  CAISO recommended the Trout Canyon Lugo 500 kV line estimated at $2 billion in the draft 2022-2023 Transmission plan but held the project back due to stakeholder input submitted to the CAISO Board.

[2] CAISO November Presentation at pp. 117, 118, 119.

[3] Letter regarding Alternative to the CAISO proposed Trout Canyon – Lugo 500 kV transmission line, Lotus Infrastructure Partners, April 25, 2023 at p. 1.

[4] 2015-2016 California ISO Transmission Plan, CAISO, March 28, 2016 at p. 111.

[5] CAISO November Presentation at pp. 12 & 117.

[6] CAISO November Presentation at pp. 12 & 119.

[7] CAISO November Presentation at p. 128.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

Based on CAISO’s analysis, the 2035 and 2040 base portfolio resources behind San Diego Gas & Electric Company (SDG&E) area constraints are deliverable with only minor operational changes and previously approved projects.[1]  Cal Advocate supports relying on non-wire solutions and previously approved transmission investments to ensure new renewable resources are deliverable.

[1] CAISO November Presentation at p. 147.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

CAISO did not present any new policy projects for the Pacific Gas and Electric Company (PG&E) service area at the November 19, 2025 meeting.[1]  Cal Advocates recommends that CAISO evaluate potential changes to PG&E’s proposed reliability projects discussed at the September 25, 2025 TPP meeting to meet additional policy needs in the PG&E area.  For example, at the September 25, 2025 TPP meeting, PG&E proposed the Eastshore and Newark Area reliability project that would reconductor approximately 92 miles of different 230 kV line segments in the project area.[2]  CAISO should assess whether operational changes, redundant battery supply, transformer reinforcement, or other lower cost alternatives can effectively address the project area’s potential reliability as well as policy needs in a more cost-effective manner.

[1] CAISO November Presentation at pp. 155-157 & 168-172.

[2] PG&E’s 2025 Request Window Proposal, CASIO 2025-2026 Transmission Planning Process (Presentation), PG&E, September 25, 2025 (PG&E Presentation) at slide 7.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

Please refer to Cal Advocates comments on the Midway Whirlwind Constraint in response to question 3.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

At this time, Cal Advocates has no comments on the Testing Results of Congestion Revenue Allocation.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

At the November 19, 2025 stakeholder meeting, CAISO explained that the forecasted MW of new load in the Bay Area are likely due to electric vehicle charging and the MW of new load in the South Bay are likely due to estimated data center demand.  For the 2025-2026 TPP cycle, CAISO is using the California Energy Commission’s 2024 California Energy Demand Update Forecast 2024-2040 (CEC’s 2024 load forecast).[1]

Cal Advocates remains concerned that PG&E continues to present new data center load in CAISO’s TPP meetings, such as the September 25, 2025 meeting that is not vetted through the CEC Integrated Energy Policy Report (IEPR) proceeding.  As stated in Cal Advocates’ comments on the 2025-2026 Draft Transmission Study Plan,[2] if the investor-owned utilities (IOUs) provide load forecasts solely to CAISO, CEC will not be a part of the data center forecast vetting, and parties to the IEPR proceeding will not have transparency into the IOUs’ forecasts.  The CEC attempts to account for uncertainty in its IEPR proceeding in a transparent and consistent manner whereas it is unclear whether or how the IOUs will account for uncertainty in demand from new data centers.  Further, the existing Memorandum of Understanding (MOU) between CAISO, the California Public Utilities Commission and CEC to coordinate transmission and resource planning explicitly states that “After the CEC finalizes the demand and load modifier forecasts and scenarios, the CPUC and the CAISO will agree on… a single recommended forecast set and seek to use it consistently in the transmission planning and resource procurement cycles.”[3]  Thus accepting PG&E’s September 25, 2025 date center load forecast deviates from the process outlined in the existing MOU in violation of its agreement terms.  Cal Advocates recommends that CAISO reject PG&E’s new data center load and proposed new data center driven projects presented at the September 25, 2025 meeting[4] in the 2025-2026 TPP cycle.  Instead, CAISO should base its reliability and policy needs assessment only on CEC’s 2024 load forecast for the 2025-2026 TPP cycle and PG&E should present any changes in their load forecast in the CEC IEPR proceeding.

[1] 2025-2026 Transmission Planning Process Unified Planning Assumptions and Study Plan, June 4, 2025 at p. 16.

[2] Cal Advocates Comments on the Draft Study Plan and February 26, 2025 Stakeholder Meeting, March 12, 2025 at p. 5.

[3] Memorandum of Understanding between the California Public Utilities Commission (CPUC) and the California Energy Commission (CEC) and the California Independent System Operator Regarding Transmission and Resource Planning and Implementation, December 23, 2022 at p. 2.

[4] PG&E’s 2025 Request Window Proposals, CAISO 2025-2026 Transmission Planning Process, September 25, 2025 at pp. 56-72.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

 No comment.

2. Please provide your organization’s comments on the MIC Expansion Requests

 No comment.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

**The first two comments (A & B) apply to all PTO planning areas.**

1. Policy Upgrades Should Be Planned as Requested by the CPUC

CAISO appears to be planning only minimal upgrades for this TPP cycle. CAISO suggested on the last stakeholder call that this is because the CPUC requested that no policy upgrades be triggered in this cycle.  This is incorrect.  As explained below, the Commission requested that transmission be planned for all renewable resources except a portion of in-state and out-of-state wind resources.

2. CAISO Should Reserve FCDS Capacity for In-State Wind

CAISO is not correctly interpreting the CPUC’s February 2025 Decision (D.25-02-026), which clearly requests that CAISO develop new transmission capacity (to the extent needed) and reserve existing and/or new transmission capacity to accommodate the in-state FCDS wind resources included in the CPUC’s adopted portfolio. (As discussed in response to Question 6, below, the CPUC excluded Northeast California wind from this request, asking that CAISO study, but not trigger, new transmission to access this area.)  In response to CalWEA’s question on the stakeholder call asking why CAISO is not proposing to reserve capacity for in-state wind, CAISO indicated that the Commission did not identify wind as a “long lead time” resource. This is incorrect, as explained below.

On page 2 of the CPUC decision (emphasis added), the Commission states, “This decision … asks the CAISO to reserve deliverability on the transmission system for certain diverse resources that are geographically-limited and take longer to develop, including geothermal, biomass, offshore wind, non-battery long duration energy storage, and a specified portion of the total amount of in-state/on-shore and out-of-state wind.”  There is no ambiguity here.

On page 58 of the CPUC decision, the Commission identifies the “open question” of “what other LLT resources [besides offshore and out-of-state wind], if any, should have reserved deliverability,” stating that:

“other LLT resources may have unique policy advantages, particularly for resource diversity. If no deliverability is reserved for certain LLT resource types that are identified by the Commission, we run the risk that transmission, once developed, may be used by resources that come online because they are easier to site, faster to come online, and currently more cost-competitive, compared to the LLT resources.”

This description is undoubtedly true for transmission deliverability identified for in-state wind.

On page 59 of the CPUC decision, the Commission goes on to “ask the CAISO to reserve deliverability for approximately 5.6 GW of in-state onshore wind as mapped in the 2035 portfolio, corresponding to the total amount of non-energy-only wind, and excluding the 1,150 MW [of in-California wind that is mapped to substations in far Northeast California and outside of the CAISO balancing area] discussed above.”  (Emphasis added.)  Similarly, on p. 60, the Commission asks CAISO to reserve capacity for only a portion of Wyoming and New Mexico wind. The Commission then “note[s] that the reservation of deliverability for diverse resources is something we intend to reevaluate with each TPP cycle,” and “also hope[s] that the reservation of TPD for diverse resource types pushes some technological resource diversity onto the existing and planned CAISO grid.”

In Ordering Paragraph 3 of the CPUC decision, the Commission summarizes its request to reserve deliverability for resources of all types, including geothermal, biomass, offshore wind, non-battery long-duration energy storage, out-of-state wind, and on-shore/in-state wind. There is no distinction between these resources in terms of some being “long lead time” and others not.  The Commission is clearly requesting that transmission be developed and reserved for all these long lead-time resources in its IRP portfolio.

This explicit request is entirely consistent with CAISO’s tariff Appendix DD section 8.9.1 and the policy stated on page 52 of CAISO’s Track 3 Updated Final Proposal, which states that eligible long lead-time resource technologies are those that are “long lead-time” (certainly true of instate wind that is dependent on new transmission), “location-constrained” (certainly true of limited instate wind resources), and “resources dependent on policy-approved transmission with explicit guidance to treat the resource as a long lead-time resource from the CPUC or local regulatory authority” (which, per above, the CPUC has provided). 

Accordingly, CAISO should develop and reserve deliverability capacity for all in-state FCDS wind resources in the CPUC’s resource portfolio for the 2025-26 plan, except for Northeast California resources, which should be studied for transmission needs in accordance with the Commission’s requests as discussed below.  Failing to do so would undermine the IRP/TPP coordination framework.

We recognize that the amount of in-state wind included in the Commission’s most recent draft portfolio for the 2026-27 TPP is lower than that contained in its 2025-26 TPP portfolio.  However, the 2026-27 resource portfolio is not final, and CAISO states that it “will update this proposal in the Draft 2025-2026 Transmission Plan (March 2026), based on stakeholder comment and the portfolios of resources we receive from the CPUC and other LRAs.” The NE California study results are needed to inform the CPUC’s decision on its 2026-27 resource portfolio and future portfolios.

3. CAISO Should Plan Windhub to Vincent Upgrades

Development of cost-effective and IRP-planned resources in the SCE Northern Area, and specifically in the Tehachapi wind resource area, has been hampered by near-zero TPD capacity for that area as well as the CAISO-imposed Windhub Substation export limit under the extreme system event criteria – potential blackout condition due to simultaneous loss of both 500kV lines from Windhub.

CalWEA’s studies show that adding a 230kV double-circuit transmission line with high-capacity double-bundle conductors from the Windhub 230kV bus to the Vincent 230kV bus would obviate the need to impose an export capacity limit at the Windhub substation.  Further, when combined with a low-cost fix (<$20M) to eliminate the ground clearance limitation for the Antelope-Vincent 500kV line, this 230kV line upgrade would add more than 3,000 MW of TPD capacity to the Tehachapi wind resource area at Windhub, Whirlwind, and/or Antelope Substations. Almost 2,000 MW of solar and wind capacity is included in the CPUC’s 2025-26 portfolio. 

Thus, CalWEA strongly recommends that CAISO consider approving the Windhub-to-Vincent 230kV line and addressing the ground clearance limitation for the Antelope Vincent 500kV line as part of its 2025-26 TPP.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

Please see the first two comments under Question 3.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

Please see the first two comments under Question 3.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

Please also see the first two comments under Question 3.

1. CAISO Should Properly Study Transmission to Northeast California

CAISO has not substantively responded to CalWEA’s earlier comments, arguing that CAISO is not properly fulfilling the CPUC’s request to study transmission solutions for 1,150 MW of wind in NE California.[1] 

The CPUC requested that CAISO study transmission solutions, including routes and potential costs, to deliver 1,150 MW of in-state (but out-of-CAISO) Northeast California wind resources, and to interface with BPA and NVE about potential regional solutions.[2]  The Commission indicated that this planning information would inform its further consideration regarding whether to plan for such transmission solutions in next year’s Transmission Planning Process.[3]  Failing to provide this study would undermine the Commission’s request and prevent it from evaluating whether to include Northeast California transmission solutions in the 2026-27 portfolios.  

In the CAISO’s slides for the Sept. 24-25, 2025, Stakeholder Meeting, CAISO acknowledges, in Slide 27, that “CPUC staff recommend CAISO conduct additional analysis and defer approving any potential transmission solutions needed for the OOS wind resources which include … 1,150 MW of Northern California wind mapped to three NVE substations.” (Emphasis added.) And yet, the diagram on p. 9 shows 1,150 MW as “Out of CAISO Imports” at Malin. Slide 27 states “in 2035 base portfolio and 2040 base and sensitivity portfolio cases, these resources are modeled off-line. Instead, we build a 2040 out-of-state wind sensitivity case to have all these resources on to study any system impact and transmission solutions that are driven by these out-of-state wind resources.”

On the September 24-25, 2025, stakeholder call, CalWEA’s consultant asked CAISO to describe the off-line modeling. CAISO responded that there is sufficient MIC to support Northeast California wind resources and, therefore, they are not modeled in the sensitivity study.  These resources are assumed to be included in import flows into CAISO.  On the November 19, 2025 stakeholder call, CAISO repeated this explanation.

CAISO’s proposal fails to fulfill the CPUC’s request.  MIC availability is very limited, and load-serving entities control its use.  It is short-term and thus generally does not support project financing. In any case, MIC is no substitute for transmission upgrades that access Northeastern California, which is a promising area for wind resource development. 

CalWEA therefore strongly urges CAISO to study 1,150 MW, as the CPUC requested, to inform the Commission’s 2026-27 TPP portfolios.[4]  While we recognize that the amount of in-state wind in Northeast California included in the Commission’s most recent draft portfolio for the 2026-27 TPP is lower than in its 2025-26 TPP portfolio, the 2026-27 resource portfolio is a preliminary draft.  The CPUC’s requested transmission study will inform the Commission’s proposed and final decisions on this portfolio.

An appropriate study would include evaluating a 230kV or 500kV substation north of the City of Susanville, along with a 230kV or 500kV line to the Round Mountain or Fern Road Substation.  Consideration should then be given to connecting this high-voltage infrastructure to the planned NVE 500kV line (as part of its Greenlink expansion project plans) in the same area.  This would offer an additional path for Northwest and Wyoming OOS wind resources to reach CAISO loads. 

2. CAISO Should Plan for Needed NGBA Upgrades, Including Collinsville to Tesla

As noted above in response to Question 3, CAISO should plan for all transmission necessary to interconnect the renewable resources in the CPUC’s 2025-26 portfolio, except for a portion of in-state and out-of-state wind resources.

CalWEA continues to recommend that CAISO consider upgrading the Tesla-to-Collinsville pathway. Furthermore, to promote more efficient use of transmission planning deliverability capacity, CAISO should follow the latest exceedance QC numbers from the CPUC’s RA proceeding for the HSN hour, i.e., approximately 50% of nameplate capacity for offshore wind projects, rather than 83%, as CAISO currently plans to use based on the 20% exceedance level during the HSN hours.  This 83% value will needlessly reserve TPD capacity for offshore wind projects that could accommodate additional interconnection customers.

The addition of the Collinsville Substation and the Collinsville-to-Pittsburg 230kV cables in the 2022-23 TPP was hampered by the fact that the Collinsville Substation became a bottleneck for deliverability capacity for practically all queued projects in PG&E’s NGBA and even for many projects in the Greater Bay Area (GBA) that did not have such a constraint before the Collinsville addition.  This concern became even more acute after CAISO approved the Fern-Road-to-Humboldt-to-Collinsville 500 kV upgrade as part of the 2023-24 TPP.  The Collinsville deliverability bottleneck will prevent Humboldt offshore wind resources from attaining FCD status.  Furthermore, CalWEA’s studies show that a relatively modest Collinsville-to-Tesla 500kV line upgrade will substantially benefit all NGBA resources, whether for short-term RA or long-term reserved capacity.  Hence, CalWEA strongly recommends that CAISO consider approving a Collinsville-to-Tesla 500kV line upgrade as part of its 2025-26 TPP.  

[1] See CalWEA’s 10-8-2025 comments, which are repeated and updated here.

[2] The CPUC stated the following in its Decision 25-02-026 (Feb. 26, 2025) (emphases added):

p. 59 “…1,150 MW of in-California wind that is mapped to substations in far Northeast California and outside of the CAISO balancing area …”

p. 62:  “[W]e will ask [CAISO] to undertake a special study of the various routes and combinations for the OOS wind amounts [including Northeast California wind] to learn more information about the details of potential routes. This will allow for analysis of alternative locations for injecting the resources onto the CAISO grid and the potential transmission solutions.”

Conclusions of Law “13. It is reasonable to request that the CAISO not trigger the approval of significant new transmission to support Northeast California wind and OOS wind on new regional transmission lines this year, but rather study these options and interface with regional partners outside of California, in order to plan for future development of this transmission with a better understanding of routing options and potential costs.”

 Ordering Paragraph 2:  “The California Public Utilities Commission (Commission) requests that the California Independent System Operator (CAISO) analyze the transmission needed for the base case portfolio reflected in Ordering Paragraph 1, but not yet trigger approval of the solutions necessary to support out-of-state wind resources on new transmission and in-state wind resources that are beyond of the CAISO balancing area and are specifically identified in the results of the mapping of resources to busbars discussed in Section 5 of this decision. Instead, the Commission recommends that the CAISO conduct the analysis and begin regional discussions (with entities responsible for regional planning and balancing areas outside of the CAISO planning area) about the appropriate siting and potential costs of such upgrades, for further consideration in next year’s Transmission Planning Process.”

[3] CPUC D. 25-02-026 at p.63 (emphasis added): “Finally, there is a similar issue with respect to in-state/on-shore wind in Northern California, where 1.1 GW of wind is mapped to the Eastern side of the Sierra Nevada mountains in the NV Energy system (not within the CAISO). This area currently has commercial interest with two projects being developed. However, the resources would currently have to connect through the Bonneville Power Administration (BPA)-NV Energy connection, which has limited capacity, and then be imported into California through the California Oregon Intertie (COI).

“Similar to the OOS wind issues generally discussed above, for this year’s TPP, we are asking the CAISO to do additional study on transmission solutions to upgrade the NVE/BPA system or directly interconnect the CAISO grid to deliver these in-state (but out-of-CAISO) wind resources. This can advance the identification of transmission locations and costs, without triggering potentially expensive or not-well-targeted solutions. This is also a complex question that requires interfacing with BPA and NVE about potential regional solutions. Thus, conducting further study this year will prepare us in next year’s TPP to actually trigger the appropriate transmission when more details are known.”

[4] CPUC’s busbar mapping shows these resources interconnected at a new substation near the existing Leavitt substation in central western Nevada (300 MW), a new substation near the existing Madeline substation (700 MW), and at the Hilltop substation (150 MW). 

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

 No comment.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

 No comment.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

 No comment.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

This is the third year that CAISO has identified the need of Lugo-Trout Canyon 500kV line to solve East of Pisgah area deliverability constraint and Lugo-Victorville constraint.  This upgrade will help multi GW of renewable resources secure deliverability, including in-state solar, out-of-state solar and wind resources.  CAISO’s Nov. 19 TPP Stakholder presentation shows that these upgrades could potentially help 7 GW of additional capacity on the SCE system and 2.3 GW of capacity East of Pisgah on the GLW/VEA system.   500kV transmission lines take a long time to site and construct, so it is important for CAISO to act to approve this upgrade instead of deferring the decision another year.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

This is the third year that CAISO has identified the need of Lugo-Trout Canyon 500kV line to solve East of Pisgah area deliverability constraint and Lugo-Victorville constraint.  This upgrade will help multi GW of renewable resources secure deliverability, including in-state solar, out-of-state solar and wind resources.  CAISO’s Nov. 19 TPP Stakholder presentation shows that these upgrades could potentially help 7 GW of additional capacity on the SCE system and 2.3 GW of capacity East of Pisgah on the GLW/VEA system.   500kV transmission lines take a long time to site and construct, so it is important for CAISO to act to approve this upgrade instead of deferring the decision another year.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

Candela Renewables provides these comments in support of LS Power’s 2025 PTO Request Window Submission for the Manning 500 kV Auxiliary Collector Substations project, as identified on slide 13 of CAISO’s presentation. The Manning area has significant solar and battery energy storage development potential, and multiple projects are seeking to interconnect to the substation through limited access pathways. The proposed collector substations would relieve this constraint by providing additional, efficient paths for current and future generation to reach the Manning 500 kV substation. By expanding the available interconnection infrastructure, the collector stations would support robust competition for the new capacity enabled by the construction of the Manning substation, which is in the public interest. As a developer seeking to interconnect generation in the vicinity of Manning, Candela submits these comments to express support for the Manning 500 kV Auxiliary Collector Substations project. The proposed collector stations would create a viable path for Candela to pursue interconnection and advance its development efforts in the area.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

The City and County of San Francisco (the “City”) appreciates the opportunity to comment on the CAISO’s 2025-26 Transmission Planning Process (TPP). The comments and questions below address the material presented at the CAISO Stakeholder meeting on November 19, 2025.

2. Please provide your organization’s comments on the MIC Expansion Requests

No comments at this time.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

No comments at this time.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

No comments at this time.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

No comments at this time.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

There Are Strong Policy Justifications in Addition to the Reliability and Strategic Justifications for CAISO to Approve WaNTEP in the Current TPP Cycle

Over the last three transmission planning cycles, the CAISO has approved a significant amount, both in scope and cost, of transmission upgrades to meet the State’s greenhouse gas reduction goals and rapid load growth. California is facing major challenges in building the transmission infrastructure that it needs, including rising costs, project feasibility, and project viability. Some challenges are driven by the need for new Right-of-Way (RoW) acquisition and environmental review, resulting in permitting delays, increased construction costs, and reduced reliability. These delays force needed generation projects and new loads to wait to come online. The cost increases are on top of the high costs and revenue requirements associated with projects developed by the original Participating Transmission Owners.

The City has proposed a unique transmission project, the Warnerville-Newark Transmission Expansion Project (“WaNTEP”), in the 2024-2025 TPP to help address these challenges. During the CAISO Board meeting on May 22, 2025, the CAISO Board of Governors (“BoG”) directed CAISO staff to continue to evaluate WaNTEP as an extension of the 2024-2025 TPP. The original scope of WaNTEP, as included in the CAISO 2024-2025 TPP Request Window, entails utilizing the City’s existing 100-mile Moccasin-Warnerville-Newark 115 kV line Right-of-Way (RoW) to rebuild a new 1,000 MW 70-mile High Voltage Direct Current (HVDC) line or a 230 kV Alternating Current (AC) line option. Based upon the CAISO’s feedback, the City is open to considering additional configurations that utilize the City’s RoW from Warnerville to Newark, including a potential Warnerville-Tesla-Newark 230 kV AC line.

In the City’s comments, dated October 9, 2025, to the CAISO, the City includes the reliability benefits associated with WaNTEP. The City noticed that the on-peak PG&E GBA deliverability constraints identified in the CAISO’s November 19^th presentation[1] are exactly the same constraints that were addressed by WaNTEP per the City’s assessment. These constraints include:

• Moraga-Castro Valley 230 kV Line;
• Pittsburg-San Mateo 230 kV Line;
• Tesla-Newark #2 230 kV Line;
• Pittsburg-Eastshore 230 kV Line
• Las Positas-Newark 230 kV Line;
• Tassajara-Newark 230 kV Line;
• Cayetano-Lone Tree (Lone Tree-USWP) 230 kV Line; and
• North Dublin-Cayetano 230 kV Cable

In addition to addressing these deliverability constraints, WaNTEP will enable the interconnection of new renewable and battery energy storage resources that were not envisioned in the 2025-2026 TPP resource portfolios.  Therefore, the City believes that WaNTEP has significant policy benefits with consistent alignment between the State and the City’s long-term goals.

In summary, the City strongly urges the CAISO to approve WaNTEP from Warnerville to Newark in the current planning cycle, given its robust reliability, policy, and economic benefits (as discussed later in response to Q.7).

[1] CAISO’s November 19^th Presentation, pp.162-165.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

The Preliminary Economic Assessment Results presented by the CAISO during the November 19^th meeting show a considerable amount of congestion on the PG&E Manning – Metcalf and Las Aguilas – Moss Landing transmission facilities.[2] For instance, the annual congestion cost on the Las Aguilas – Moss Landing 230 kV line, subject to PG&E N-1 Manning-Metcalf 500 kV outage, is as high as $105.6 million in 2040. The City believes that WaNTEP would reduce this congestion cost as it offers a parallel path to the Las Aguilas – Moss Landing 230 kV line for GBA imports. The City urges the CAISO to evaluate the economic/congestion benefits of WaNTEP under the N-1 Manning-Metcalf 500 kV outage in addition to the reliability and policy benefits discussed earlier.

[2] CAISO’s November 19^th Presentation, p.206.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

No comments at this time.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

No comments at this time.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

Clearway appreciates the opportunity to comment on CAISO’s 2025-2026 TPP Preliminary Policy Assessment Results. Within the 2040 base case, the results show 7.2 GW of undeliverable capacity. Approval of the Trout Canyon to Lugo 500kV line upgrade would make this portfolio capacity deliverable. Additionally, an upgrade at the Sagebrush interconnection would alleviate some of the deliverability constraints and address reliability issues at a very low cost. Clearway recommends that CAISO approve both upgrades in this Transmission Plan. 

Together, the Trout-Lugo 500 kV line and the Sagebrush Interconnection upgrades would allow for a significant increase in deliverable capacity and address reliability issues in the area. The need for the Trout Canyon to Lugo upgrade has been identified in multiple TPP cycles and the upgrade was previously recommended for approval in the draft 2022-23 TPP. However, the upgrade was removed shortly before final approval because of the possibility of an alternative project (Mead-Adelanto upgrade or “MAP upgrade”) that was proposed late in the TPP cycle by a then-owner of the Mead-Adelanto transmission line. The MAP upgrade does not seem to be a viable solution: It is unclear from public information what the project’s status is under its current ownership, and more importantly, it does not address all the constraints identified in this cycle. In the 2024-25 TPP, the need for the Trout Canyon to Lugo upgrade persisted, but the upgrade was not approved.  

With a continuation of the need for portfolio deliverability as well as reliability, Clearway recommends that the Trout Canyon to Lugo upgrade and Sagebrush interconnection be recommended for approval in the 2025-26 TPP. It is imperative that CAISO approves an upgrade to increase deliverability from East of Pisgah in this TPP cycle, otherwise the reliability problems and lack of deliverable capacity will continue to get worse and will eventually require a more expensive upgrade in the future. FERC Order No. 1920, which mandates longer-term planning to increase the pace of transmission grid expansion, coupled with the fact that major transmission upgrades take over a decade to complete, necessitate an upgrade in this region in this TPP.    

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

Environmental Defense Fund (EDF) values the opportunity to submit comments to CAISO on the 2025-2026 Transmission Planning Process Policy and Economic Preliminary Study Updates. EDF greatly appreciates CAISO’s continued efforts to advance the reliability of California’s grid and urges CAISO to take a “least regrets strategy” in planning for long-lead-time resources, particularly offshore wind.

EDF supports the two proposed Recommended Reliability Projects of less than $50 million. Both the Walnut 230 kV Short-Circuit Duty Circuit Breaker Upgrade and Oro Loma 70 kV Area Reinforcement Project are cost-effective projects that maintain grid stability amid expected load growth.

2. Please provide your organization’s comments on the MIC Expansion Requests

EDF has no comments at this time.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

EDF has no comments at this time.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

EDF has no comments at this time.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

EDF has no comments at this time.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

EDF encourages CAISO to plan toward meeting its Sensitivity Portfolio, which reveals the transmission implications of a portfolio with a greater share of long lead-time resources as called for in D.24-08-064. In particular, EDF notes the importance of preparing the infrastructure necessary to interconnect offshore wind in the PG&E Kern Interconnection Area and the PG&E North of Greater Bay Area Interconnection Area.

Recognizing that California will ultimately require more offshore wind included in either the Base or Sensitivity portfolios to achieve the state’s 25 GW by 2045 goal, EDF recommends planning for at least 7.6 GW of offshore wind by 2035 (as reflected in the Sensitivity Portfolio). Given the forthcoming Western regional energy market could substantially reduce wind procurement cost, and the Bureau of Ocean Management has already granted five leases for offshore wind sites totaling 10 GW of potential offshore wind capacity, EDF further recommends that CAISO consider planning for the full 10 GW. EDF notes this approach would position California’s offshore wind resources to support other states if market conditions align under the new Western regional energy market structure.

EDF urges CAISO to adopt a least-regrets strategy that ensures adequate transmission capacity, reduces future congestion, and avoids costly late-stage build outs. Underbuilding now would risk future system reliability and increase long-term ratepayer costs.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

EDF has no comments at this time.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

EDF has no comments at this time.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

EDF supports CAISO’s proposal to include offshore wind and out-of-state wind as long-lead-time resources eligible for deliverability reservations in the draft transmission plan. However, EDF is concerned about CAISO’s proposal to exclude in-state onshore wind from deliverability reservations. This proposal is inconsistent with CPUC’s Decision 25-02-026 in Rulemaking (R.) 20-05-003, which recommends CAISO to reserve deliverability for approximately 5.6 GW of in-state onshore wind in the 2025-2026 Transmission Planning Process. EDF does not see the need for this deviation at this time.

EDF notes that reserving deliverability provides a market signal for development and excluding onshore wind from deliverability reservations risks having available transmission capacity absorbed by resources that come online faster.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

EDF power solutions (“EDFps”) supports the approval of the recommended reliability projects costing less than $50 million. We appreciate CAISO’s effort to streamline the approval of these actionable projects. 

2. Please provide your organization’s comments on the MIC Expansion Requests

While EDFps acknowledges that the MIC Expansion Request process represents an iterative improvement, it has not yet delivered the sufficient, meaningful structural changes required for the overall MIC framework. We strongly encourage CAISO to continue active collaboration with stakeholders through parallel initiatives to resolve persistent deficiencies in the current MIC process and to develop more effective, comprehensive enhancements.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

EDFps is concerned by the reliance on Remedial Action Schemes (RAS) to mitigate severe on-peak constraints in the SCE area, particularly for the Midway–Whirlwind 500 kV line and North of Lugo constraints like the Calcite-Lugo 230 kV line, which shows overloads up to 181% in 2040.

While RAS is a useful interim tool, the magnitude of these overloads suggests a structural deficit.

We strongly support prioritizing physical transmission upgrades ("new wires"), such as the rebuild of Lugo-Calcite or the Trout Canyon-Lugo line, over the stacking of additional RASs. Over-subscribing RAS in critical corridors increases operational complexity and risk. Firm capacity provided by new wires allows for the deliverability of renewable generation, whereas RAS solves reliability by curtailing the very resources we aim to integrate.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

No comments at this time.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

No comments at this time.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

The preliminary results indicate massive renewable curtailment in the PG&E Fresno area of over 7,000 GWh in the 2040 base portfolio. This level of trapped generation indicates a severe lack of export capability that cannot be solved by battery storage dispatch alone.

We strongly support moving forward with physical upgrades to the Gates-Panoche and Panoche-Schindler corridors. Relying on storage charging to mitigate overloads of this scale is a temporary fix that does not solve the fundamental inability to move abundant solar energy to load centers during peak production. We urge CAISO to recommend new wires solutions here to align transmission capacity with the state's renewable investment in the Central Valley.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

The economic analysis reveals a startling increase in congestion costs, specifically $1.24 billion on Path 15 and $350 million on Path 26 in the 2035 timeframe. These figures represent a clear economic signal that the current grid configuration is inefficient and significantly costing ratepayers.

We believe that congestion costs exceeding $1 billion annually on a primary backbone path like Path 15 justify immediate and substantial physical transmission reinforcement. We support CAISO prioritizing the Path 15 and Path 26 corridors as high-priority economic projects in this planning cycle. 

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

EDFps appreciates CAISO’s initiative to test new methodologies for congestion revenue allocation in preparation for EDAM.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

To better understand how the final plan will be developed, we request CAISO staff answer the following questions regarding the hierarchy of solutions:

1. How specifically does the CAISO determine when a constraint has graduated from being managed by RAS to requiring a physical upgrade? Is there a specific metric regarding the frequency of RAS arming, the volume of generation dropped, or the complexity of the scheme that triggers a transition to a wires solution?

2. When comparing a storage-based mitigation (e.g., virtual storage mapping) against a transmission upgrade, how does CAISO weigh the operational longevity of the solution? Does CAISO account for the risk that storage resources may not materialize at the precise mapped locations?

3. Does the CAISO have a defined limit for RAS saturation in specific corridors (e.g., SCE North of Lugo or Path 15) where adding further schemes is deemed operationally imprudent regardless of the estimated cost savings? 

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

Fervo Energy Company (“Fervo”) appreciates the CAISO sharing its 2025-2026 Transmission Planning Process (“TPP”) policy and economic study results during the stakeholder call on November 19th. Fervo thanks the CAISO for its continued commitment to planning for the State’s inter-regional power delivery needs and engaging stakeholders in this process. 

Fervo is a leading developer of utility-scale EGS projects, leveraging advanced drilling and subsurface technologies to access new geothermal heat resources previously deemed unsuitable due to limitations in conventional geothermal drilling methods. EGS already provides reliable, clean, and dispatchable power today and is rapidly scaling to meet the energy demands of the future.    

Fervo has a portfolio of lease holdings across the West, including in California, and is actively developing projects to support the California grid, including the 500-megawatt Cape Station project in Beaver County, Utah. All 500 megawatts are fully contracted with California Load Serving Entities (“LSE”), including Southern California Edison (“SCE”), Ava Community Energy, Clean Power Alliance (“CPA”), Desert Community Energy, and Shell Energy, to meet procurement orders under D.21-06-035.  

Fervo strongly urges the CAISO to prioritize and act upon known resource constraints in the East of Pisgah region which limit the state’s ability to integrate diverse and firm resources. The East of Pisgah constraint in particular has been known to limit California’s clean and reliability power goals for several years and Fervo urges the CAISO to make investments in these regional upgrades immediately as stalling is resulting in a compounded deliverability issues for developers and LSEs alike. Given that the constraint has been well understood and recorded in the TPP for several years, we urge the CAISO to accelerate the discussions on upgrades and avoid forestalling progress. 

Additionally, Fervo asks that the CAISO comprehensively examine geothermal deliverability reservations, as geothermal availability across the West has evolved significantly over recent years. The CAISO’s November 19th presentation stated that deliverability reservations for the 2025-26 TPP cycle would be held at the same volumes as in the 2024-25 cycle, with no new reservations. This conclusion does not align with the significant increases in out-of-state geothermal availability as indicated in the CPUC busbar mapping for the 2025-26 cycle. For example, the 2024-25 TPP cycle reserved only 950 MW of geothermal at the Mirage and Imperial Valley substations.1  However, the CPUC-approved portfolio for the 2025-26 TPP shows that geothermal resources were mapped to various additional locations, including Nevada and Utah.2  Fervo urges the CAISO to examine the geothermal deliverability reservation updates to ensure that this TPP aligns with CAISO’s established process to integrate the preceding busbar mapping results.  

Fervo thanks the CAISO for its commitment to stakeholder engagement and coordination. 

1. https://stakeholdercenter.caiso.com/InitiativeDocuments/BoardApproved-2024-2025-TransmissionPlan.pdf, p. 20.

2. see Compact-Dashboard_25-26TPP_BaseCaseD_2025-02-20.xlsx, summary by RESOLVE area.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

No comment.

2. Please provide your organization’s comments on the MIC Expansion Requests

No comment.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

No comment.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

No comment.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

No comment.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

Please see our response to Question 7 regarding preliminary economic analysis.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

(This comment responds to preliminary economic analysis, as well as the preliminary policy assessment results for the PG&E Fresno area.)

Golden State Clean Energy (“GSCE”) submitted the Valley Clean Infrastructure Plan (“VCIP”) to CAISO during the request window of the current TPP cycle. In addition to the reliability benefits noted in that submittal, GSCE urges CAISO to consider how VCIP can help address policy issues, including integrating Fresno area portfolio resources, and provide economic benefits associated with Path 15 corridor congestion and Fresno area curtailment. The VCIP transmission infrastructure includes collector substations and 500 kV lines that connect these substations to the backbone grid, allowing for more efficient large-scale resource development while avoiding exacerbating issues on the 230 kV and low voltage system. Westlands Water District has issued a notice of availability of the Final Program Environmental Impact Report for VCIP.

Policy analysis of the Fresno area and the interaction with economic analysis

For this 2025-26 TPP cycle, the CPUC provided CAISO with a base case that includes 13.5 GW of solar and 5.1 GW of battery storage in the Fresno transmission area. This portfolio capacity appears by 2040, within the 15-year study horizon. California law requires the CPUC to produce 15-year resource projections “to ensure adequate lead time for the Independent System Operator to analyze and approve transmission development . . .”[1]  The California Legislature noted its intent that CAISO take notice of this policy of studying 15-year portfolios to partner with the CPUC and proactively develop transmission.[2]

The CPUC is currently developing its base case for the next TPP cycle. The latest draft base case shows a significant increase in the amount of solar needed in the near-term.  The base case portfolio includes almost 36 GW of new solar by 2031.  This would require a solar build rate that would accelerate to about ~7 GW per year by 2030. The CPUC has not yet finalized its busbar mapping and the future location of this solar is yet to be determined. Many commenters expressed concerns with achieving the solar buildout in the CPUC’s draft portfolios in the necessary timeframe. GSCE’s comments urge the Commission to issue final portfolios with Fresno area solar that are at least consistent with the current portfolio and strong commercial interest.  In any event, it is clear that the CAISO system will require significantly more solar in the near-term timeframe to meet policy and reliability needs. We believe that continuing to study at least 13.5 GW of solar in the Fresno Area in this TPP cycle remains important for keeping the State on track to affordably meet greenhouse gas reduction goals and reliability needs.  

In the current portfolio, the CPUC, when considering numerous developmental hurdles and land use and environmental policies, deemed Fresno as warranting transmission upgrades to enable at least 13.5 GW of solar and 5.1 GW of battery storage. The CPUC’s estimate of policy-driven upgrades to support solar Fresno area resources was about $3.6 billion.  In contrast, GSCE estimates the cost of the VCIP 500 kV transmission system to be approximately $2.5 billion, which can unlock 20 GW of solar and 20 GW of battery storage. VCIP can integrate more Fresno area capacity at a much lower cost and avoid more costly upgrades, providing an affordable option for meeting the solar identified in the base case.

GSCE proposed VCIP in this TPP cycle’s request window due to its reliability benefits. GSCE also urges CAISO consider how VCIP can address policy and economic issues identified in the region. Further analysis is warranted, especially considering that Westlands Water District is nearing completion of the programmatic environmental review of VCIP.

Preliminary economic analysis – Path 15 corridor

CAISO’s preliminary economic analysis identifies the Path 15 corridor as the costliest congestion on the CAISO system. For the Path 15 corridor, CAISO identified about $1.24 billion in total congestion cost in 2035 and about $1.32 billion in total congestion cost in 2040.[3]  This represents nearly a billion dollars in additional congestion cost on the Path 15 corridor relative to the last TPP cycle, and the last cycle already started to observe significant and growing congestion on the Path 15 corridor.

Additional 500 kV lines are needed to alleviate the congestion on this corridor and allow for more economic energy delivery to the Greater Bay Area and other parts of Norther California that are currently unable to fully access Southern California solar resources. GSCE has proposed the Monarch Transmission Project as a potential solution to the Path 15 corridor, as provided in our economic study request submitted earlier in this TPP cycle.

The Department of Market Monitoring is already starting to observe similar congestion trends to those observed on the Path 15 corridor in the TPP. DMM’s 2024 annual market report states that, “[t]he primary constraints affecting day-ahead market prices were the Gates-Midway #1 500 kV, Moss Landing-Las Aguilas #1 230 kV, and Tesla-Los Banos #1 500 kV lines,” all of which are lines north of the Midway Substation that separate the Greater Bay Area from Southern California generation resources.[4]  DMM observed that the congestion on these lines was usually in the south to north direction, raising prices for PG&E customers. “The percentage of hours in which congestion impacted DLAP prices increased each year from 2022 to 2024. Overall, in 2024, PG&E experienced congestion in 75 percent of hours—an increase from 60 percent in 2023.”   Figure 5.10 from DMM’s 2024 annual market report shows how congestion routinely increases prices in PG&E, and that in 2024, congestion remarkably increased prices in PG&E in the third quarter.

Preliminary economic analysis – Fresno area resources

Not only does the Path 15 corridor need a solution to address significant congestion that is preventing low-cost solar energy from flowing to the Greater Bay Area and elsewhere in Northern California, but there is also an economic justification to identify a transmission solution to integrating more solar in the Fresno area. A broader Northern California reinforcement project is needed for the region that addresses both the Path 15 corridor, Fresno area resources, and Greater Bay Area load. VCIP should play an important part of that regional upgrade.

Once the full amount of Fresno area solar provided in the 15-year study horizon is built out by 2040, Fresno will experience the highest curtailment ratio by far of any renewable resource zone if new transmission is not built.[5]  CAISO observes that the Fresno renewable zone has over 15% of its total potential energy production curtailed in 2040, nearly 5% higher than the next most curtailed renewable zone. Such a high rate of curtailment suggests transmission upgrades are needed to economically integrate the amount of new renewables called for by the CPUC.

GSCE urges CAISO to explore the benefits associated with connecting Fresno area resources directly to new substations the 500 kV backbone, consistent with the VCIP design.  This can allow more delivery of Fresno solar while avoiding many of the known Fresno area lower voltage issues. If planned in coordination with Westlands Water District, the VCIP infrastructure can provide a more cost-effective solution to reducing curtailment in Fresno while enabling future portfolio resources to interconnect. 

CAISO also observed that the significant increase in Fresno area resources this cycle played a substantial role in providing pushback flow on the Path 26 corridor. The Path 26 corridor is another area of the grid that historically has faced costly congestion. We request that CAISO consider the economic value that is provided by Fresno resources when reducing Path 26 corridor congestion due to pushback flow, and this value should further justify transmission upgrades that can integrate Fresno area resources.

[1] Pub. Util. Code § 454.57(e)(1)

[2] Pub. Util. Code § 454.57(c)

[3] CAISO presentation, at 198, 203, Nov. 19, 2025

[4] CAISO DMM, 2024 Annual Report on Market Issues and Performance, at 180, Aug. 2025

[5] CAISO presentation, at 217, Nov. 19, 2025

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

GSCE appreciates the examination of how congestion revenue is allocated in TEAM and supports the potential changes to TEAM that CAISO is exploring. The TEAM approach taken to congestion revenue over the past several years may have resulted in reductions in congestion being negated by the reduction in congestion revenue, which risks defeating the purpose of an economic assessment meant to reduce congestion. The potential changes that CAISO discussed at the November 19 stakeholder meeting seem to address that issue and thus allow the reduction in congestion to properly highlight the benefits of reduced congestion. GSCE appreciates CAISO’s effort in this complicated but important issue.

GSCE also supports the use of any updated TEAM approach to congestion revenue in this TPP cycle, including the ability for the updated approach to justify projects as solutions in the economic assessment. At the least, the updated approach should be used alongside the previous approach to compare the results, and a BCR of 1.0 in either approach should be sufficient to support approval of an economic project.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

No comment.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

GridLiance West (“GLW”) applauds the California Independent System Operator’s (“CAISO”) efforts in drafting the 2025-26 Transmission Planning Process (“TPP”) and its strategic and proactive approach towards the transmission build-out needed to achieve the state’s transition to 100% clean energy while maintaining grid reliability. GLW would like to take this opportunity to highlight that the Trout Canyon–Lugo 500 kV line project more effectively mitigates broader system constraints when compared to the following proposed alternatives:

• Eldorado – Lugo 500 kV Line Circuit 2
• Marketplace – Adelanto AC-DC Conversion

In its Board Approved 2022–2023 TPP analyses, CAISO highlighted the Trout Canyon – Lugo 500 kV line effectiveness in addressing the Lugo – Victorville 500 kV constraint. These analyses found that the principal alternative, an Eldorado – Lugo 500 kV Line Circuit 2, would require an additional Sloan Canyon – Eldorado 500 kV line circuit, resulting in numerous line crossings in an already congested corridor. Additionally, the Eldorado – Lugo alternative and the Marketplace – Adelanto Project would not mitigate the GLW deliverability constraint or improve the deliverability of resources mapped to the VEA planning area that are served by GLW owned transmission. By contrast, the Trout Canyon – Lugo 500 kV line would improve the deliverability of resources in the VEA planning area, mitigating both GLW 230 kV area constraints and the Lugo – Victorville constraint.

While the Trout Canyon–Lugo project has been under consideration by the CAISO since the 2022–2023 TPP cycle, it has not advanced. In the intervening years, the deliverability constraints at the Lugo–Victorville 500 kV interface, originally the primary driver for introducing the project, have continued to increase, in addition to several other system constraints. GLW urges the CAISO to move forward with a robust solution that alleviates the Lugo–Victorville constraint and enables deliverability of resources mapped in the GLW/VEA planning area to the CAISO.

Since the 2023 TPP, CAISO has mapped significantly larger amounts of generation behind the key 2035 base-case on-peak constraints, further underscoring the urgency of action. Generation behind the GLW constraint has risen to 2,952 MW—a 31% increase from the 2,253 MW identified in 2023. Behind the Lugo – Victorville constraint, generation has increased to 15,924 MW, up 130% from 6,895 MW in the 2023 TPP. At the Eldorado – McCullough constraint, 9,343 MW of generation is now blocked, compared to 6,896 MW in the 2023 Draft TPP, when this constraint appeared only in the off-peak case. Since then, Eldorado – McCullough has become an on-peak constraint, with a corresponding increase in the amount of generation affected. This development further demonstrates that the system conditions underlying the initial justification for the Trout Canyon–Lugo project have significantly intensified, reinforcing the project’s necessity in addressing East of Pisgah deliverability constraints and enabling CAISO to meet the state’s long-term renewable energy targets.

In addition, new constraints have emerged at Sloan Canyon – Eldorado since 2023 which neither the Marketplace – Adelanto AC – DC Conversion nor the Eldorado – Lugo 500 kV Line Circuit 2 can help alleviate. The Trout Canyon – Lugo project remains the only identified transmission solution capable of alleviating all four of these constraints. In its Board Approved 2024-2025 TPP analyses, CAISO highlighted short-circuit duty (SCD) issues at Eldorado 500 kV bus resulting from CAISO, LADWP, and NV Energy queued generation, as well as several planned transmission upgrades to serve that generation. These SCD issues are exacerbated by adding any new 500 kV connections at the Eldorado bus, meaning an alternative such as Eldorado–Lugo Circuit 2 would worsen the known issue and trigger additional projects to mitigate the SCD. In contrast, a new Trout Canyon–Lugo line would avoid creating additional SCD impacts at Eldorado while resolving all four identified deliverability constraints, making it the more effective and efficient overall solution.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

 No comments

2. Please provide your organization’s comments on the MIC Expansion Requests

 No comments

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

The Regenerate California Coalition’s comments are focused on three areas in the SCE transmission network.  They are: 1) the SCE Metro Area; 2) the SCE Northern Area and; 3) the SCE East of Pisgah Area. 

SCE Metro Area – Regenerate is pleased to see that the need for the Serrano-Del Amo- Mesa 500 kV reinforcement project can be offset by the strategic placement of large-scale batteries in the SCE Metro Area.  This result clearly demonstrates that batteries can serve as an alternative to major transmission projects as well as a resource that can be dispatched (both charging and discharging) in the market to meet load cost-effectively. It also shows the need for a more coordinated approach between the California Public Utilities Commission (CPUC) and the California Independent System Operator (CAISO) for considering the integration of batteries into the transmission planning process.   

Regenerate supports the evaluation of additional Metro Area transmission projects that can address the SSN (3 pm to 6 pm) constraint that limits the amount of solar power that can be delivered into the SCE Metro Area. It is critically important for meeting the state’s climate goals that batteries located in the SCE Metro Area and elsewhere be charged with zero-carbon electricity, rather than by gas-fired generation. It is clear that batteries can offset the need for fossil generation located in the SCE Metro Area. Regenerate recommends that in future iterations of the IRP and TPP, modeling should be conducted that assumes some fossil generation in the area will be off.  Such an analysis will help parties understand where SSN and HSN transmission constraints will emerge as more renewable energy is developed and where BESS can be optimally placed to meet that demand.

SCE Northern Area – This area includes the Antelope Valley area of Kern and Los Angeles Counties where a large amount of solar and wind development has been built since the development of the Tehachapi Regional Transmission Project (TRTP). Two of the major substations in the TRTP, Windhub and Whirlwind and associated transmission lines, are bottlenecks that restrict the flow of renewable energy to load centers. The CAISO identifies 811 MW of renewable energy as being undeliverable behind the Windhub constraint and 1,268 MW as being undeliverable behind the Whirlwind constraint in the 2035 Base Case portfolio.

The CAISO staff has identified three transmission projects that could mitigate the Windhub constraint and four transmission projects that could mitigate the Whirlwind constraint.  Regenerate supports a detailed evaluation of those alternatives. In addition to evaluating the impact of each project on reducing congestion on Path 26 and in the SCE Metro Area, the CAISO should also analyze the impact of these projects on the operation of gas-fired generation in the SCE Metro Area.  

There are indications in the current IRP process that more solar and storage should be located in the Kern and Fresno areas of the Central Valley and less in the Western Arizona area. More Central Valley power should have a positive impact on the predominant south-to-north power flows on Path 26. The CAISO analysis of the alternative transmission projects should be sensitive to this possible shift in the locations of future solar and storage projects and preserve optionality for more development in the Central Valley.

SCE East of Pisgah Area – Much of this area is located in Southern Nevada and includes the transmission infrastructure owned by GridLiance West.  It also includes the Harry Allen, the Eldorado and the Mohave substations which are important hubs for serving CAISO load. It is at these substations that a very large amount of out-of-state wind and some geothermal power will be delivered. Currently, it is not clear what additional transmission infrastructure will be developed to get power from the two principal resource-rich wind areas, New Mexico and Wyoming, to the CAISO system. The CAISO has indicated that it intends to consult with the regional planning entities, NorthernGrid and WestConnect, and others to identify transmission corridors from these resource-rich areas. Regenerate supports these efforts.

Based on the 2035 base case portfolio, there will be a substantial amount of undeliverable clean energy resources (5,130 MW) located behind the Lugo -Victorville transmission constraint. The CAISO staff has identified three significant transmission projects as alternative ways to mitigate this constraint. They are: 1) a new Trout Canyon to Lugo 500 kV line; 2) a new Eldorado to Lugo 500 kV line and; 3)  the conversion of the existing Marketplace to Adelanto 500 kV line to a Direct Current (DC) transmission project with two new DC converter stations. 

Regenerate supports an analysis of the costs and the benefits of these three alternative projects through CAISO’s production cost modeling process to determine overall impacts to the grid and costs to ratepayers. Given the uncertainty as to how a large amount of out-of-state wind will be delivered to the CAISO system, Regenerate recommends that the CAISO not take any action regarding these projects in the 2025-2026 TPP. We believe that California ratepayers will benefit from further analysis that could be conducted in the 2026-2027 TPP.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

The GridLiance West (GLW) system includes approximately 165 miles of 230 kV transmission lines in Southern Nevada. It includes the Sloan Canyon 500 kV substation which connects to the Eldorado and Harry Allen substations.  

Regenerate notes that there is a considerable amount of clean energy resources that could potentially be developed in the GLW area by 2040.  However, getting the power from the GLW system to load centers in California will require that new transmission be developed to either the Lugo or Adelanto substations. The CAISO identifies the Sloan Canyon to Lugo 500 kV as a way of mitigating the undeliverable power in the GLW system.  

Regenerate recommends that  the CAISO not evaluate mitigations for the undeliverable load from this area in isolation. The evaluation of transmission alternatives for the GLW constraint should also consider the Lugo – Victorville constraint. As noted above for the Lugo-Victorville constraint, Regenerate recommends that the CAISO not approve a mitigation solution for the GLW constraint in the 2025-2026 TPP.  It should be considered in the 2026-2027 TPP.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

 No comments.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

Regenerate observes that there will be a significant amount of costly congestion along Path 15 for the base case portfolio in 2035 and 2040. There is also a sizable amount of curtailment that would occur in the Fresno and Kern renewable areas of the PG&E system in 2035 and 2040.  The Kern and Fresno areas are among the most important areas in California for the development of solar and battery storage resources. By 2040 the base case portfolio shows 19,131 megawatts of solar nameplate capacity and 43,004 megawatts hours of storage capacity. These resources would be developed north of Path 26 and would mitigate congestion on that portion of the CAISO system. Regenerate would support transmission projects that can significantly mitigate congestion and curtailment from solar and storage projects in the Central Valley and that could reduce the use of gas-fired power plants in the Central Valley, the Greater Bay Area, and the SCE Metro Area. 

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

Regenerate supports the framework for studying the 12 proposed transmission projects nominated by independent parties. We agree that these projects should be evaluated on how they mitigate congestion in the Path 15 corridor, the Manning to Metcalf 500 kV line, the Las Aguilas to Moss Landing 230 kV line, the Path 26 corridor and the SCE Metro 230 kV transmission system. 

In addition, Regenerate requests that the CAISO evaluate the impact of the selected transmission projects on reducing the need for local resource adequacy in the SCE Metro area.  Additionally, the CAISO should consider broader reliability and resiliency benefits of developing an additional transmission path to the SCE Metro area.  

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

Regenerate generally supports improvement to the modeling of the allocation of congestion revenues based on the principle of cost causation. We agree that congestion revenues should be allocated in an equitable and transparent manner to promote the most efficient use of the transmission system. 

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

Despite clear mandates, Non-Wires Alternatives (NWAs)—such as energy storage, distributed generation, and demand response—face structural and technical barriers in the Transmission Planning Process. These barriers can impede the realization of the economic and environmental advantages of these solutions.  

One barrier is the assumption about the limited discharge duration for battery storage that would be relied upon to effectively mitigate a transmission constraint.  It is not clear from the CAISO presentation how this limitation is evaluated.  It would be very helpful for the CAISO to specify the amount of megawatt hours of battery storage that would be needed to overcome specific transmission constraints in future presentations. 

Participating Transmission Owners have a financial disincentive to support NWAs and therefore are unlikely to bring them forward for consideration by the CAISO. Under current cost-of-service regulation, transmission owners earn an established rate of return on their capital investments.  NWAs, on the other hand, are often structured as service contracts, which the counterparty typically expenses. If done right, choosing a NWA to mitigate a transmission constraint has the potential to lower transmission revenue requirements.

Additionally, there is a fundamental mismatch between the transmission planning cycle and the procurement processes for Load Serving Entities that are supervised by the CPUC. When the CAISO approves a transmission line in the TPP, it can effectively order a participating transmission owner to build it or conduct a competitive solicitation to determine who will build the transmission project.  If the CAISO were to select an NWA, it is not clear how it would order it to be built. This lack of clarity about the process is a significant barrier for NWAs being carefully considered in the TPP. If the CAISO identifies a suitable NWA, it should define the elements of that alternative specifically enough that the CPUC will be able to move towards implementing that alternative without onerous additional analysis.

Regenerate appreciates the operational complexity that the CAISO faces in integrating NWAs into the market and using them in the transmission planning process.  We appreciate that the CAISO has launched a Demand and Distributed Energy Market Integration working group.  We are optimistic that this working group will bring forward practical solutions to enable behind-the-meter and distribution-connected resources to be integrated into the wholesale markets. These enhancements should be carried forward into the Transmission Planning Process.  

Finally, the CAISO stakeholder presentation included for some projects an evaluation sheet that showed that remedial action schemes, changes to the deployment of batteries and the use of grid enhancing technologies were considered as alternatives for mitigating transmission constraints. It would be very helpful for the CAISO to provide to stakeholders a more detailed presentation as to how these alternatives were evaluated.  

Thank you for considering these comments. We look forward to working with you on these issues.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

Intersect appreciates and supports CAISO’s comprehensive and forward-looking transmission planning process. Intersect also supports LS Power’s Manning 500 kV Auxiliary Collector Substations proposal. The area surrounding the Manning substation in Fresno County offers high-quality solar resources and developable land well-suited for utility-scale projects, making it a valuable location for future clean energy development. Expanding interconnection capability through the proposed auxiliary collector substations would enable additional cost-effective renewable generation in this promising region and further advance California’s SB 100 goals.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

NextEra Energy Resources, LLC commends the CAISO for its analysis showing a need for a new 500 kV transmission line to solve multiple constraints in the East of Pisgah area. This is a step in the right direction, and we look forward to seeing a specific transmission solution recommended in the transmission plan. As shown in the 22-23 TPP and CAISO’s 20-year Transmission Outlook, a new line is essential to deliver resources in the East of Pisgah area, where multiple IRP cycles have transmitted portfolios of cost-effective renewables with demonstrated commercial interest.  Once again, the need for a new 500 kV line is evident. The CAISO should not delay in approving a wires solution in this TPP cycle.

In past TPP cycles, CAISO has excessively relied upon Remedial Action Schemes (RAS) and other load shedding and congestion management solutions which do not provide deliverability for the 16+ GW of solar and battery resources seeking to interconnect in GridLiance West, LLC’s (GLW) queue. Due to lack of available Transmission Plan Deliverability (TPD) in the East of Pisgah area, some projects have converted to energy-only. But the economics of energy-only projects in CAISO are challenging and unlikely to result in projects reaching Commercial Online Date (COD). Therefore, NextEra Energy Resources is pleased to see more sensible results indicating a new transmission solution.

While successive CPUC portfolios have transmitted sizable resource builds in the East of Pisgah area, dating back to the 22-23 TPP, the newest (preliminary) busbar mapping results (for the 26-27 TPP) trend towards even greater resource builds: e.g., ~6.2 GW of solar by 2036 (up from ~2.4 GW of solar in this TPP cycle).  This trend further bolsters the conclusion that a new 500 kV line should be approved in this TPP cycle.

Further amplifying the need for new transmission infrastructure, the 2024 IEPR demand forecast to be used in the next TPP cycle has increased by 4.4 GW statewide by 2035, driven by new electrification and data center growth. To get ahead of this increase in demand, CAISO must build more transmission; congestion management and other low-cost solutions will not suffice.  As shown in CPUC’s draft portfolios for the 26-27 TPP, vast amounts of renewables and storage resources must be built to serve this load coming from developable resource zones like East of Pisgah.

NextEra Energy Resources believes the Trout Canyon – Lugo 500 kV line alternative is likely superior due to its effectiveness, lower cost, and lower risk. First, the Trout Canyon – Lugo 500 kV line solves all the 2035/2040 East of Pisgah on- and -off peak constraints, whereas other alternatives, such as the Marketplace – Adelanto AC-DC conversion (MAP) project, do not. The MAP project does not address chronic limiters in VEA/GLW system, whereas the Trout Canyon – Lugo 500 kV project can relieve the internal VEA/GLW overloads on various 138/230 kV lines. In addition, the MAP project aggravates congestion on Path 26, the Sloan Canyon – Eldorado 500 kV, and Eldorado – McCullough 500 kV lines.1]  Second, the MAP project’s initial $1.1 billion cost estimate provided to CAISO in 22-23 TPP is no longer accurate. Given the significant cost escalation of HVDC equipment, a more accurate estimate is $2.7 billion.[2] By comparison, the Trout Canyon – Lugo 500 kV line does not involve HVDC conversion equipment and was initially estimated at $1.5 -  2 billion.[3] Third, the MAP project presents schedule risks due to the global demand for HVDC converter stations.[4]CAISO should seek updated cost estimates for all transmission alternatives and approve the best alternative that cost-effectively solves multiple constraints.

For all these reasons, NextEra Energy Resources respectfully requests CAISO to approve a new 500 kV line to solve the East of Pisgah constraints in this cycle, and not wait for next cycle. Notwithstanding the out-of-state wind study CPUC has requested CAISO to conduct, it is clear that approving a new line in this cycle is not only least-regrets, it is long overdue.

[1] CAISO 2024-2025 Transmission Plan, Appendix G.

[2] GridLiance West, LLC Letter submitted to CAISO in the 2022-2023 TPP, dated May 17, 2023.

[3] CAISO 2024-2025 Transmission Plan, Appendix F.

.[4] CAISO Addendum to Metcalf and Newark Approved Project Sponsor Selection Reports

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

Pattern Energy offers these comments in support of the 2025-2026 Transmission Planning Process.

Introduction

Pattern Energy is one of the world’s largest privately-owned developers and operators of wind, solar, transmission, and energy storage projects, and one of California’s largest suppliers of clean power with more than 2 GW of operational wind generation serving California customers in addition to the 3,650 MW SunZia Wind facilities currently under construction and the 550-mi, 3 GW SunZia Transmission HVDC system recently completed by Pattern’s affiliate SunZia Transmission, LLC. Pattern Energy is headquartered in San Francisco, California and is guided by a long-term commitment to serve customers, protect the environment, and strengthen communities.

We support the ISO’s efforts to expand regional transmission and enable resource diversity. Reliability and affordability benefits come with the technologically and geographically diverse resource portfolio the ISO is planning for, of which high capacity-factor inter-regional wind is a critical component. To this end, we understand the ISO and the CPUC are working together to make no-regrets transmission investment decisions by studying various ways to integrate the incoming Out-of-State (“OOS”) resources, with some discretion in resources delivery locations. 

A. The CAISO Should Study Interdependence of Northern and Southern Los Angeles 500kV Deliverability Constraints

Recent TPP studies and the 20-year transmission outlook have made clear that some level of in-state upgrades will be required to enable the delivery of OOS resources to CAISO load. Focusing on the southern area, one primary constraint that can only be mitigated through a new significant transmission project is the Lugo-Victorville constraint, located along the northern 500kV path into Los Angeles load from the east.  The Lugo-Victorville constraint is well known and has surfaced in previous TPP studies. Another constraint identified in this year’s TPP is the Serrano-Alberhill-Valley constraint, located along the southern 500kV path into Los Angeles load from the east.  The Serrano-Alberhill-Valley constraint was previously identified and mitigated via rating increases; identification of this constraint in this year’s TPP suggests persistent instances of congestion in the area and further mitigation would also require a new significant transmission enhancement.

Both the Northern and Southern 500kV paths to Los Angeles from the east are critical import points for OOS resources. The CAISO should evaluate future bulk upgrades in the southern area to address the impacts and benefits to the entire southern area, including both the Lugo-Victorville constraint and the Serrano-Alberhill-Valley constraint. Where possible, infrastructure portfolios that relieve both constraints most efficiently should be considered.

B. The CAISO Should Analyze Additional Sensitivities to Evaluate the Efficacy of Planning to Different OOS Import Points.  

Pattern suggests that the CAISO complete a sensitivity study analogous to the Wyoming Wind sensitivity completed during the 2024-2025 TPP.  The CAISO should analyze the impacts of different OOS resource import points on the Lugo-Victorville and the Serrano-Alberhill-Valley constraints. Specifically, Pattern suggests the CAISO analyze the impacts of alternate delivery points of 1,750 MW of OOS wind from New Mexico currently mapped to the Lugo substation which seemingly is contemplated to be delivered via a merchant-developed >700-mile HVDC project spanning 3-4 states. Pattern recently submitted comments to the CPUC busbar mapping process regarding this HVDC project, explaining that such a project would be extremely difficult and expensive to develop within the IRP/TPP planning horizon.

Where there is out-of-state resources without clear candidate transmission projects – such as the wind targeted for delivery to Lugo Substation –  Pattern recommends that the CAISO assume these imports are delivered to import interfaces using long-term firm transmission service, namely the existing Willow Beach and Palo Verde import points which have high levels of MIC potential.  The CAISO could also map OOS resources to existing liquid scheduling points geographically close to the CAISO border (where new transmission infrastructure to the border has lower development risk) such as Westwing. The CAISO should take this approach because merchant transmission is more difficult to justify across difficult-to-permit areas and alternatives such as the use of available transmission service may, especially in the near-term, be a more advantageous option. Assuming the New Mexico wind arrives at or near the CAISO border via scheduling points (rather than assuming merchant transmission is going to extend into CAISO load pockets) creates flexibility for transmission developers to build cost-effective, less complex-to-permit projects where they are required.  This also enables out-of-state generation developers to retain optionality for final delivery points based on the most optimal transmission upgrade portfolio within the CAISO’s existing boundaries.

Pattern recommends that the CAISO work with the CPUC to refine a busbar map of OOS resources using these import points that results in the most cost-effective portfolio of required upgrades. CAISO should make sure resource delivery remains within the limits of existing and planned Available Transmission Capacity (ATC) offered by non-CAISO Transmission Service Providers serving the mapped import points. Transmission service is currently available for delivery to both Willow Beach and Palo Verde from various points of receipt from western New Mexico. Moreover, Pattern recognizes and appreciates the CAISO’s participation in interregional transmission planning studies conducted through WestTEC, and suggests considering any transmission projects identified by the WestTEC studies which could enable New Mexico wind development when refining the busbar map of OOS resources.

Pattern Energy appreciates the opportunity to comment on the 2025-2026 TPP.  We support the CAISO’s development of critical transmission infrastructure and appreciate the CAISO’s efforts to plan for the most optimal delivery solutions for both in-state and OOS resources.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

No comments.

2. Please provide your organization’s comments on the MIC Expansion Requests

No comments.

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

No comments.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

No comments.

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

No comments.

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

No comments.

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

No comments.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

No comments.

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

The City of Santa Clara, dba Silicon Valley Power (SVP), appreciates the opportunity to provide these comments on the November 19, 2025, Transmission Planning Process (TPP) Stakeholder meeting. In particular, SVP wishes to reiterate its significant concerns regarding PG&E’s request for “concurrence” of certain data center load interconnections set forth in PG&E’s September 25, 2025, Request Window Proposals.  The load related to the proposed interconnections was not included in the studies that resulted in the Preliminary Reliability Results for the Greater Bay Area, nor was the load included in the studies that resulted in the Final Reliability Assessment Results posted on October 31, 2025.  As explained in detail in SVP’s October 9, 2025 comments on the September 24-25 Transmission Planning Process meeting (October 9 Comments)[1], the “concurrence” sought by PG&E in its September 25, 2025 Request Window Proposals for the data center load interconnections included in PG&E’s Load Cluster 2024 and Serial Interconnection Studies, and PG&E’s proposed “Capacity Upgrade” projects triggered by the serial loads (slides 57-72 of PG&E’s September 25, 2025 Presentation), would cause significant contingency overloads on key SVP import facilities, putting SVP’s system, as well as the reliability of the Greater Bay Area, in jeopardy. 

SVP Urges the CAISO to Reject PG&E’s Unusual Request for “Concurrence” to Ensure a Comprehensive Regional Transmission Planning Assessment of the Reliability Needs in the South Bay

Although PG&E would have CAISO believe that incremental large loads seeking transmission capacity in a short timeline is a brand-new phenomenon that CAISO has not seen before, it most certainly is not.  In 2016, SVP realized that the requests for transmission capacity within the City by large load customers were far outpacing the load forecast included in the Integrated Energy Policy Report (IEPR) developed by the California Energy Commission (CEC) and used by CAISO in its TPP studies.  In 2018, SVP attempted to convince PG&E to include verifiable SVP load forecasts in PG&E’s submittals to the CEC; those discussions failed.  In September 2020, SVP reached out to the CEC to discuss the IEPR load forecast for SVP, explaining that the TPP reliability report did not show infrastructure improvements in the PG&E system that would allow SVP to meet its anticipated near-term exponential load growth, since SVP’s most recent load forecast was only used in CAISO sensitivity cases, rather than as a base case.[2]  SVP’s outreach to the CEC resulted in a series of discussions and SVP’s provision of evidence that SVP’s load projections were more than just conjecture and speculation; that these loads were “real” and verifiable, they were large, and they were coming to Santa Clara.  It was only when these forecasted loads were fully vetted and assessed that the CEC included them in their IEPR, and CAISO included them as base case in the TPP studies.

PG&E, it appears, is seeking to sidestep this process.  In seeking the CAISO’s “concurrence” in the 2025-2026 Transmission Planning Process that it may move forward with the interconnection of hundreds of MW of anticipated data center load, PG&E seeks to avoid the process prescribed by the CAISO.  Unlike PG&E, SVP dutifully followed the CAISO process, which helps ensure the reliability of not only SVP’s service territory but the entire South Bay. SVP identified an exponential increase in demand over a short period and accordingly sought to have this load included in the CEC’s IEPR (together with any vetting and assessment the CEC requires to substantiate the timing of the anticipated load) so that CAISO can include the vetted load in its base case (not merely in sensitivity studies) and ensure a comprehensive regional transmission planning assessment of the reliability needs in the South Bay.

PG&E should not be permitted to add an incremental 920 MW of data center load at this stage, which is not modeled in the 2025-2026 TPP Base Case, upending the CAISO’s process. If allowed, this renders the Final Reliability Results Assessment for the Greater Bay Area, at least as pertains to the South Bay, meaningless.  Moreover, if PG&E is permitted to circumvent CAISO’s process and interconnect these data center loads before they can be included in comprehensive studies, what would prevent others from doing the same?  For these reasons, along with the technical reasons set forth in SVP’s October 9 Comments, SVP urges CAISO to reject PG&E’s request for “concurrence.” At a minimum, PG&E should be required to submit these new loads to the CEC for review and assessment under the CEC 2025 IEPR, which will enable CAISO to perform a more comprehensive regional transmission planning assessment of the reliability needs in the South Bay in its 2026-2027 TPP. 

If PG&E’s anticipated data center loads are included in the CEC 2025 IEPR, and therefore included in the CAISO’s 2026-2027 TPP studies, SVP must be (1) provided the opportunity to conduct affected system studies in coordination with the CAISO, LS Power, and PG&E, to assess the potential adverse impacts the anticipated PG&E data center loads would cause on the reliability of SVP’s system; and (2) included in any discussions regarding the need to expand CAISO OP7340 and/or the need for a remedial action scheme determined necessary to accommodate PG&E’s anticipated data center loads as a result of CAISO’s 2026-2027 TPP assessment.

SVP, as should be expected of other interested stakeholders, closely follows and adheres to CAISO’s annual process of developing a detailed study plan using the CEC’s demand forecasts and the CPUC’s resource portfolios. Those load and resource forecasts are used in performing the sequential technical studies to develop a comprehensive transmission plan with recommended projects, which is ultimately submitted to the CAISO Board for approval.  PG&E should be required to follow the same process as all other entities and submit its load forecast for vetting and inclusion at the beginning of CAISO’s cyclical process.  Failing to do so not only would allow PG&E to circumvent CAISO’s established planning framework, but would also undermine the integrity of CAISO’s broader effort to ensure a reliable and well-coordinated transmission system for the entire region.

[1] See SVP October 9 comments located at  https://stakeholdercenter.caiso.com/Comments/AllComments/2cd110fd-8815-46b5-887a-fcf3e85603a2#org-0b4c5039-3ce5-4c8f-9a43-260598e66f67

[2] See SVP Comments on the 2020-2021 Transmission Planning Process Preliminary Reliability Assessment Results and PTO Request Window Submissions, dated October 8, 2020.

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

Sonoma Clean Power (SCP) appreciates CAISO’s continued commitment to identifying smaller scale reliability projects that maintain essential grid performance. SCP does not offer project specific comments at this time. However, SCP reiterates its broader position that where reliability driven upgrades can be right sized to also provide incremental deliverability benefits in highly constrained regions, particularly the North of Greater Bay Area (NGBA), CAISO should prioritize such dual purpose solutions. As SCP has noted in past filings, targeted reliability enhancements near substations such as Collinsville, Tesla or Delavan may be capable of unlocking Transmission Plan Deliverability (TPD) without introducing significant additional scope or cost. This type of optimization aligns with CAISO’s obligation to ensure efficient use of the transmission system and advances the state’s clean energy and reliability goals.? 

2. Please provide your organization’s comments on the MIC Expansion Requests

SCP has no comments on the MIC Expansion Requests at this time. 

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

Upgrades to address the Midway-Whirlwind Path 26 constraint could represent a significant portion of the investment approved in the 2025-26 TPP.  To maximize cost-effectiveness, SCP recommends the CAISO frame the mitigation as something that is eligible for both new technologies (reconductoring with advanced conductors) and competitive solicitation - stand alone additional transmission lines, particularly now that SB 254 improves the ability to leverage public financing.  A competitive solicitation that allows PG&E to offer a reconductoring upgrade alongside standalone alternatives from competitive bidders will maximize benefits 

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

SCP has no comments on the GLW area policy assessment results at this time. 

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

SCP has no comments on the SDG&E area policy assessment results at this time. 

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

SCP appreciates CAISO’s analysis of emerging needs in the PG&E area and offers several key observations based on persistent constraints affecting renewable development in Northern California. 

Deliverability Scarcity in the NGBA 

SCP reiterates concerns, documented consistently in prior filings, that TPD scarcity in the North of Greater Bay Area has stalled renewable development despite proximity to major 230 kV and 500 kV transmission corridors. SCP has seen firsthand how TPD scarcity complicates the advancement of geothermal, long duration energy storage (LDES), and other long lead time resources, while driving up procurement costs for Northern California LSEs.  SCP urges the CAISO to approve a 2025-26 TPP that creates additional deliverability in PG&E NGBA, to avoid blocking-out high-value diverse resources in the region seeking to enter Cluster 16. 

Path 26 Constraint Absent in CPUC Modeling 

CAISO confirmed at the November 19 workshop that the Path 26 upgrade that appears needed in this TPP was not part of the whitepaper upgrades provided to the CPUC for modeling, and SCP understands that the version of RESOLVE used for the 2025-26 TPP did not enforce a Path 26 constraint, which is thankfully rectified in the version informing next year’s plan. . This omission may skew portfolio outcomes toward Southern California siting and increase dependence on long distance transfers across an already congested northward path. SCP strongly encourages CAISO to work with CPUC to: 

• Improve the representation of Path 26 constraints in future IRP modeling 

• Evaluate alternative portfolios with higher Northern California siting 

• Compare the cost effectiveness of Path 26 upgrades to targeted reinforcements that increase Northern California deliverability 

Collinsville, Delavan, and Tesla Area Constraints 

SCP remains concerned that the Collinsville, Tesla and Delavan constraints, though acknowledged by CAISO, do not yet fully appear in TPP results. For the past 3 years, TPD has been unavailable in PG&E NGBA due to large-scale area deliverability constraints that are left unaddressed in TPP upgrades.  The CPUC sought to remedy this disconnect, which is caused by TPD locked up by projects in the queue that aren’t in the CPUC’s portfolios, through the “unaccounted for TPD” adjustments included in the busbar mapping used for this TPP.  The CPUC even flagged a Collinsville-Tesla upgrade as being “high” likelihood in the busbar mapping.  SCP was thus surprised that the constraints limiting TPD are not yet showing up in this year’s TPP.

SCP requests the CAISO provide a detailed justification on why upgrades addressing PG&E NGBA constraints are not yet necessary for supporting the CPUC’s portfolio, which included 4.2 GW of resources in 2035 in the region—especially given the region’s unique ability to support resource diversity.  The justification should include an estimate of TPD availability with the proposed portfolio, and if it continues to be zero, a strategy on how to address the disconnect between the scope of TPP upgrades and GIDAP.  

SCP also echoes prior recommendations that CAISO reassess the Collinsville to Humboldt 500 kV project, which may provide near term deliverability and congestion benefits if reconfigured to a phased project through Vaca Dixon. 

Geysers 115 kV Upgrades 

On the November 19th call, CAISO explained that the 115 kV upgrades near the Geysers will be facilitated through LDNUs funded by interconnection customers.  SCP requests clarification on why similar Geysers 115 kV upgrades were treated differently across TPP cycles, one funded as a TPP project (the 2024-25 TPP 115 kV reconductoring between Eagle Rock and Silverado) and others categorized as LDNUs (the 115 kV upgrades in this TPP). Given CPUC’s designation of geothermal as a long lead time resource and the severity of constraints at Eagle Rock, Cloverdale, and Hopland shown in CAISO’s own deliverability assessments, SCP urges CAISO to consider policy driven eligibility for 115 kV upgrades in the region.  Requiring interconnection customers to fund extremely large-scale LDNUs creates a significant barrier for development and puts the CPUC’s need for geothermal capacity in the region at-risk if the project funding the upgrades withdraws from the queue. 

Birds Landing - Contra Costa 230 kV constraint 

SCP is concerned about the Birds Landing-Contra Costa 230 kV constraint, which continues to appear as a binding interface in CAISO’s deliverability analysis. This constraint affects multiple North Coast and inland PG&E substations and is particularly consequential for offshore wind, Central Valley solar, and geothermal integration. As highlighted in prior SCP/RCEA comments, Birds Landing-Contra Costa is a nested constraint whose remediation could enable multiple classes of resources simultaneously. SCP recommends that CAISO elevate Birds Landing-Contra Costa as a candidate for near term policy driven action and publish a sensitivity quantifying TPD unlocked and corresponding congestion reduction. 

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

SCP supports CAISO’s effort to integrate congestion and deliverability considerations into economic study work and offers the following recommendations: 

CAISO’s PCM results consistently identify Path 15 as the most economically congested corridor in California, with congestion rising from $389 million in 2034 to $522 million in 2039. SCP recommends that CAISO evaluate whether incremental TPD, enabling upgrades in Northern California, especially those addressing Delavan and Collinsville constraints, could reduce this congestion by improving north, south transfer flexibility. This aligns with SCP/RCEA’s prior recommendations to classify such upgrades as economic, driven projects when multi-value benefits are demonstrated. 

Additionally, SCP encourages CAISO to recognize that an upgrade providing even modest relief of the Birds Landing-Contra Costa constraint could have meaningful economic effects. As a nested constraint limiting deliverability for offshore wind, Central Valley solar, and geothermal, Birds Landing-Contra Costa is responsible for recurring redispatch costs and CRR underfunding. Its mitigation may offer measurable congestion reduction consistent with CAISO’s multi value economic criteria. 

For all of the constraints mentioned, Midway-Whirlwind, Collinsville, Delavan, Tesla, Birds Landing-Contra Costa, SCP urges CAISO to quantify: 

• Marginal congestion reduction 

• Increased TPD availability 

• Reduction in CRR underfunding 

• Improved utilization of existing PG&E 500 kV backbone 

SCP supports aligning CAISO’s economic assessment framework with the multi-value planning requirements of FERC Order 1920 A, which emphasize holistic evaluation of deliverability, congestion relief, local reliability, and resource adequacy. SCP’s previous comments explicitly encouraged CAISO to quantify marginal congestion reduction from incremental upgrades and to treat solutions that provide broad system benefits as candidates for policy or economic driven approval. 

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

SCP does not offer specific comments on the congestion revenue allocation results at this time, but reiterates the connection between severe TPD bottlenecks and recurring CRR underfunding. SCP notes that upgrades in the Delavan, Collinsville, Tesla corridor may mitigate both deliverability scarcity and financial inefficiencies.? 

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

SCP underscores that Northern California continues to face the most acute intersection of deliverability scarcity, high congestion, and unmet long lead time resource needs in the state. Targeted upgrades addressing the Collinsville, Delavan, and Tesla constraints, combined with updated modeling of Path 26, represent the most impactful near term opportunities to advance California’s climate, reliability, and affordability goals. 

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

Terra-Gen urges CAISO to address the Windhub Area Constraint through the Windhub-Vincent 230 kV double-circuit transmission line upgrade rather than through removal of 203 MW of generic resources at the Windhub substation. This approach better aligns with CAISO’s reliability objectives, least-regrets planning principles, and California’s long-term decarbonization and affordability goals.?

Prioritize Strong Resource Areas

Windhub is directly connected to some of California’s strongest renewable resource areas, including Tehachapi and the Mojave Desert, with a proven development track record and substantial interest. Terra-Gen is aware of multiple projects totaling 800 MW in the interconnect queue that are connecting to the Windhub substation as energy-only. The Windhub-Vincent 230kV Project would create 2,500 MW of deliverability at Windhub and support the immediate development of an additional 1,500 MW of new fully deliverable solar capacity on the proposed gen-ties without requiring additional substation expansion. Assigning or increasing new IRP resources at Windhub takes advantage of California’s strongest renewable resource areas, reducing overbuild, curtailment, and integration costs compared to shifting capacity to weaker areas, while removing 203 MW would move the portfolio away from these least-cost, highest-value locations.?

Resolve Reliability Risks

Removing resources at Windhub would also leave the underlying reliability risk associated with the Windhub Area Constraint unresolved, whereas the Windhub-Vincent upgrade would directly mitigate risks such as adverse stability or cascading outage conditions. Because it both fixes a known reliability issue and unlocks high-value renewable generation needed in multiple planning futures, the upgrade should be considered a “low regrets” project.?

Affordability

As California builds toward SB 100 targets, substations in strong renewable corridors like Windhub will see increasing flows and capacity assignments, making transmission reinforcement a prerequisite to reliably integrating required renewables rather than an optional enhancement. By enabling additional capacity by 2030, the Windhub-Vincent project also allows projects to capture time-limited federal tax incentives, lowering levelized costs and supporting ratepayer affordability—benefits that are not realized if 203 MW at Windhub are simply removed.

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting

1. Please provide your organization’s comments on the Recommended Reliability Projects less than $50 million

2. Please provide your organization’s comments on the MIC Expansion Requests

3. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SCE area

4. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the GLW area

5. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the SDG&E area

6. Please provide your organization’s comments on the Preliminary Policy Assessment Results for the PG&E area

7. Please provide your organization’s comments on the Preliminary Economic Analysis Results

EXECUTIVE SUMMARY

Viridon Path 15 LLC ("Viridon") submits the following comments on the 2025-2026 Transmission Planning Process (“TPP”) Policy and Economic Preliminary Assessment and Study Updates presented on November 19, 2025 (“November 2025 Preliminary Assessment”), and respectfully requests that the California Independent System Operator (“CAISO”) evaluate the alternative transmission solutions outlined below to address congestion on the Path 15 corridor, which CAISO has identified as a high-priority economic study area.

Viridon is a CAISO Participating Transmission Owner with an economic interest in the Los Banos–Gates #3 500 kV (“LBG3”) line, one of the three 500 kV lines comprising Path 15.

CAISO's preliminary production cost simulations presented on November 19^th revealed sharply increasing congestion in the Path 15 corridor. In the 2035 base portfolio, Path 15 is projected to face more than $1.2 billion in annual total congestion. By comparison, Path 26—the next most congested area on the CAISO system—is estimated to incur roughly $350 million in congestion.[1] In the 2040 Base Portfolio, Path 15 congestion burden grows to more than $1.3 billion, while Path 26 is projected to experience ~$370 million in congestion costs.[2] Combined with PG&E's receipt of approximately 10 GW in new data center load applications[3]_­—nearly doubling from 5.5 GW at year-end 2024[4]—and the concentration of new generation resources in southern California and the Central Valley, California’s primary north-south transmission corridor faces unprecedented strain requiring immediate action.

Viridon has identified a suite of rapidly deployable upgrade options using Grid Enhancing Technologies (“GETs”) that can deliver substantial near-term congestion relief and increased transfer capability.  The GETs solutions discussed below can serve as either standalone solutions or building blocks for longer-term transmission reinforcement needs. They can be implemented within existing rights-of-way at a fraction of the cost and timeline of greenfield transmission lines.

Viridon seeks CAISO’s consideration of a comprehensive evaluation of these alternatives alongside long-term solutions identified in the preliminary assessment, recognizing that the urgency of California's reliability needs and climate goals, along with affordability and equity priorities, require both near-term relief and long-term capacity expansion.

PROBLEM STATEMENT: ESCALATING CONGESTION, UNPRECEDENTED LOAD GROWTH & EXPANDING GENERATION PORTFOLIOS ARE INTENSIFYING PRESSURES ON PATH 15

1. CAISO’s Path 15 Congestion Projections Show Rapid and Significant Escalation

The 2025-26 TPP preliminary Production Cost Modeling (“PCM”) results reveal accelerating and accentuated congestion on Path 15:

This escalating congestion on Path 15 is further exacerbating price disparity between northern and southern California transmission customers. Preliminary economic results indicate that the projected Locational Marginal Price (“LMP”) spread between the PG&E Bay Area and the SCE/SDG&E areas would more than double over the next 10 to 15 years relative to the 2024-25 TPP projections.[6]

Additionally, these Path 15 limitations could significantly impact the value the CAISO can deliver through the Extended Day-Ahead Market (“EDAM”). Transfers through California between northern and southern EDAM entities will be limited by congestion on Path 15.

The above results represent significant, tangible economic losses and costs to California ratepayers, which are expected to continue to worsen as load and generation patterns evolve.

2. Data Center Development is Driving Concentrated Load Growth in the Bay Area, North of Path 15

PG&E’s service territory is experiencing a substantial and unprecedented increase in projected load growth north of Path 15 in the Bay Area, driven primarily by large data center development. PG&E has received to date a total of 10 GW of new data center load applications—up from 5.5 GW at the end of 2024—which reflects a fundamental shift in California’s future transmission needs. This includes:

• Close to 2 GW of data center load in implementation phase interconnecting to San Jose by 2029
• 8 GW of additional data center load planned to be in study phase by 2031, with half projected to be under study by 2028.

These figures reflect only PG&E’s current load interconnection requests and do not account for other potential data center load projects within northern California municipal utilities, or proposals such as the 700-900 MW data center load connecting by 2030 at the Manning Substation, along Path 15. Large block load additions of this magnitude represent a major change in future grid needs and underscore the urgency of strengthening intra-regional transfer capability to meet these emerging demands.

3. Resource Development Patterns Exacerbate Transmission Constraints

The CPUC's IRP portfolios for the 2025-26 TPP demonstrate that congestion is expected to worsen absent targeted transmission upgrades indicated by:

• The majority of new resources being planned south of Los Banos
• The CPUC staff being forced to remap resources to less optimal northern California locations to avoid further Path 15/26 overloads[7]
• Solar resources mapped to the Fresno area showing significant increases, reaching 4.4 GW in the next 10 years vs. 3.6 GW in the previous TPP, and 13.6 GW in the next 15 years, up from 5.8 GW[8]
• CPUC staff’s post-ruling remapping reallocating additional solar and storage to several PG&E substations, including 500 MW of solar and 100 MW of 8-hour battery storage at Manning 230 kV.

Critically, the CPUC's least-cost portfolio for the 2026-27 TPP selects Path 15/26 expansion tranches of up to 5.5 GW by 2045,[9] supporting the economic necessity of upgrading these corridors. Specific CPUC findings reinforce this conclusion:

• The first 1 GW transmission expansion tranche is selected as early as 2036, scaling up to 5.5 GW by 2045 based on load growth projections
• RESOLVE modeling shows upgrades provide 450 GW of added north-to-south flows by 2036, increasing to 3,800 GW by 2045[10]
• The third tranche of Path 15/26 upgrades (>2.5 GW) are triggered in all sensitivity cases except the single case with higher carbon emissions[11]
• CPUC analysis indicates these upgrades are necessary even just to serve PG&E's projected load, until offshore wind is delivering energy into PG&E's service area.[12]

Furthermore, the Darden Clean Energy Project, with 1,150 MW of solar and up to 4,600 MWh of battery storage, is not currently modeled on the Manning – Midway 500 kV line (part of Path 15) in the studied portfolios and could further exacerbate Path 15 congestion issues, underscoring the urgent need to increase the path’s capacity.

In parallel, the areas around the Manning Substation, and the LBG3 line more generally, have some of the most active commercial interest for new renewable resource buildout in the CAISO system.  Developing resources in this area and providing deliverability will be critical to meeting long policy and reliability needs.

VIRIDON PATH 15 PROPOSED SOLUTIONS: RAPIDLY DEPLOYABLE & COST-EFFECTIVE

Based on extensive due diligence on upgrade alternatives, Viridon respectfully requests CAISO to evaluate the following grid reinforcement options (“Proposed Solutions”), which can be deployed rapidly:

1. Mid-line Series Compensation on LBG3

• LBG3 is currently the only 500?kV line in the Path?15 that lacks series compensation, leaving it under-utilized while the two compensated 500 kV lines in the path carry most of the flow. Installing a mid-line series capacitor will align LBG3’s impedance with the other Path 15 500kV lines and redistribute flows off the congested eastern lines. This allows for a more balanced system and greater overall utilization of the Path 15 corridor
• Compensation improves power flow distribution and increases transfer limits immediately in a highly cost-effective manner
• Implementation is within existing rights-of-way and does not require a Certificate of Public Convenience and Necessity (“CPCN”).[13]

2. Reconductoring LBG3 with Advanced Conductors

• Results in increased transfer capability and thermal rating of LBG3 using high-temperature, low-sag advanced conductors[14]
• Thermal ratings could be increased to more than twice their current limits
• Estimated to cost less than half of the cost of a new 500 kV line
• Utilizes existing rights-of-way and structures
• Can be done “live” with minimal outages, based on extensive due diligence conducted with industry-leading engineering and construction consultants.

3. Tap into Manning Substation

• Creates a new 500 kV interconnection point along the Los Banos-Gates #3 line connecting from the mid-line series compensation station proposed above into Manning
• Relieves concentration and reliability risk by providing an alternative path for the significant load and generation currently funneling through the Manning substation
• Addresses vulnerability where multiple large-scale projects converge at a single point
• Provides system flexibility and redundancy for both new generation resources and growing data center loads upstream and in the Path 15 region.
• Balances system topology with all three Los Banos–Gates EHV lines having a similar midpoint.

3. SmartValve Power Flow Control

• Modular static synchronous series compensator provides dynamic control to optimize economic dispatch, actively minimize congestion costs and improve market efficiency as conditions change throughout the day
• Redirects power off overloaded elements and onto underutilized lines
• Particularly valuable given Path 15's diverse resource mix (solar, wind, hydro, storage)
• Can mitigate subsynchronous resonance issues in series-compensated networks[15]
• Installation can be synergistic with installation of mid-line series compensation.

These Proposed Solutions can be deployed at a significantly lower cost and on a much faster timeline than greenfield transmission projects while providing substantial qualitative and quantitative benefits—whether implemented individually or as a coordinated set of upgrades—as demonstrated in the next section. Moreover, implementing these solutions simultaneously would create efficiencies by leveraging shared engineering, permitting, and construction mobilization, avoiding duplicative outages, and delivering a more versatile upgrade framework that can better accommodate future system needs and evolving load and generation patterns.

QUANTIFIED BENEFITS: ECONOMIC AND TRANSFER CAPABILITY ANALYSES

Comprehensive economic and transfer capability assessments demonstrate that the Proposed Solutions can significantly reduce congestion and price disparity, lower renewable curtailment, increase system throughput, and deliver substantial economic and policy benefits to the CAISO grid.

1. Production Cost Modeling Results

Viridon has performed production-cost modeling using Hitachi's Gridview application in accordance with CAISO’s Production Cost Modeling methodology, applying the recently released preliminary 2025-26 TPP cases[16] to the 2035 Base. Viridon evaluated the cumulative impact of a set of proposed solutions and, for additional context, also analyzed their performance when combined with complementary transmission reinforcement south of Path 15 (see scenario B below). This analysis yields the following results in comparison with the Base case:

These preliminary results are based on Viridon’s combined set of proposed upgrades, i.e, mid-line series compensation, reconductoring and a tap into Manning Substation.[17] In parallel, Viridon is continuing production-cost analyses for each individual proposed solution to further inform CAISO’s evaluation, particularly as the 2025-26 TPP cases continue to be refined.

The scenario with additional potential reinforcement south of Path 15 was included to capture broader system impacts, develop a more comprehensive solution, and illustrates how complementary upgrades can further improve congestion performance across the corridor. The analyzed reinforcement—a new Gates–Midway 500 kV line to the south—was selected primarily because it represents the most influential downstream 500 kV corridor affecting Path 15 flows. Additional reinforcement north of Path 15 was also included in Viridon’s PCM[18] but did not yield further benefits beyond the ones presented above. These more comprehensive scenarios are offered as representative configurations to understand full corridor benefits (beyond Path 15), recognizing that CAISO’s broader system assessment will define the most effective reinforcements to pursue.

2. Value of Quicker Congestion Relief

Implementing series compensation on LGB3, reconductoring the line with advanced conductors, and tying into Manning offers a near-term, high-value opportunity to address Path 15 congestion far sooner than any greenfield alternative. Reconductoring and series compensation can be deployed at least five years faster than a new 500 kV transmission line, allowing the system to tackle escalating congestion on an accelerated timeline and avoiding prolonged economic impacts. By delivering meaningful transfer capacity increases well ahead of long-lead time greenfield projects, these enhancements provide earlier and more substantial congestion relief. Preliminary analysis indicates that advancing this congestion relief by five years could yield approximately $2.7 billion in total savings[19] to California ratepayers, reflecting reduced congestion costs, lower curtailment, and improved system efficiency during the period before a new greenfield line could come online.

3. Transfer Capability Benefits

Viridon conducted transfer capability analyses to assess how its proposed upgrades would affect power flow across the Path 15 corridor, both on LBG3 specifically and on Path 15 as a whole when combined with complementary system reinforcements.

Viridon’s transfer capability results[20] show:

3. • Flow on LBG3 would increase substantially with reconductoring and 70% series compensation: by over 110% in the south-to-north direction and approximately 120% in the north-to-south direction.

   • When combined with complementary reinforcements north and south of Path 15—an additional Gates–Midway 500 kV line and an additional Los Banos–Tracy 500 kV line—Viridon's proposed LBG3 upgrades (reconductoring, 70% series compensation, and Manning tie) would increase Path 15's total south-to-north transfer capability, as defined in the WECC Path Rating Catalog, by ~1,000 MW under both winter and summer ratings.

4. Capital Cost Savings Analysis

Viridon performed analysis of the potential benefits of enhancing the capacity of the Path 15 and 26 corridors using the CPUC's RESOLVE tool. RESOLVE assesses the least-cost buildout of generating and storage resources, as well as major transmission upgrades necessary for meeting California’s carbon and reliability goals. The RESOLVE analysis showed:

• Without Path 15/26 upgrades, California would pay nearly $3 billion more to reliably serve load and meet carbon goals[21]

• Similarly, absent Path 15/26 upgrades, systemwide curtailments across PG&E, SCE, and SDG&E services areas are estimated to be 15% higher[22]

• An upgrade solution deployable by 2030 (comparable to Viridon's fastest option) is chosen by the CPUC’s RESOLVE model in its earliest available year and is estimated to save California ratepayers over $900 million in the net present value of resource buildout costs.[23]

These capital buildout savings are in addition to the congestion and curtailment benefits identified above.

Viridon’s proposed solutions offer a highly cost-effective and rapidly implementable pathway to relieving the severe congestion on Path 15 and integrating needed renewable generation to meet increasing load. By leveraging targeted, in-corridor upgrades that can be deployed within existing rights-of-way, these alternatives deliver meaningful reductions in congestion and improved power flow distribution on timelines far shorter than new greenfield transmission projects and at a much lower cost to California ratepayers. Notably, preliminary analysis shows that these upgrades, coupled with downstream upgrade, can yield congestion-relief benefits comparable to those of significantly larger and substantially more expensive greenfield solutions, such as a new Whirlwind–Tesla HVDC line, and on a much faster timeline.[24] As a result, Viridon’s portfolio provides a practical, near-term means to address urgent system needs while complementing longer-term transmission expansion.

RECOMMENDATIONS TO CAISO

1. Conduct Comprehensive Evaluation of Viridon Path 15 Alternatives

We respectfully request that CAISO's policy and economic assessment explicitly evaluate Viridon's proposed upgrade options. While each of the proposed upgrades can be assessed individually, evaluating them in isolation understates their full potential. These measures are complementary, and implementing them as a coordinated solution set unlocks significant engineering, permitting and construction efficiencies, while minimizing duplicative outages, and improving overall system performance along the Path 15 corridor. The combined solution set also offers greater versatility to accommodate future load growth and generation shifts. For these reasons, a comprehensive assessment—considering both individual upgrades and the integrated set—is essential to identifying the most cost-effective and timely congestion-relief.

The evaluation should consider:

• Reduction in Path 15 total congestion cost
• Reduction in LMP spread between northern and southern California
• Reduction in renewable curtailment
• Policy support for IRP renewable and storage buildout necessary to meeting California’s carbon and reliability goals
• Implementation timeline advantages, including faster congestion relief compared to greenfield solutions
• Cost-effectiveness
• Flexibility to integrate with broader solutions CAISO may be considering for the broader north-south corridor.

2. Prioritize Solutions Based on Exceptional Congestion Costs

Given the projected $1.2 billion annual congestion cost on Path 15, assuming the 2035 Base portfolio, CAISO should prioritize solutions that can materially increase transfer capability and address congestion on expedited timelines. The benefit-cost analysis should give greater weight to the value of early implementation.

3. Coordinate with CPUC Portfolio Findings

CPUC's least-cost analysis, as part of the ongoing development of the portfolio for the 2026-27 TPP, selects Path 15/26 expansion, with benefits including:

• 450 GWh of added north-to-south flows and 7,450 GWh of added south-to-north flows by 2036[25]
• Up to 3,700 GWh of added north-to-south flows and 22,000 GWhs of added south-to-north flows by 2045[26]
• Mitigation of congestion in both directions[27]
• Support for California's carbon reduction goals.

CONCLUSION

Viridon appreciates the opportunity to provide these comments and stands ready to work collaboratively with CAISO to identify solutions that can provide near-term congestion relief while supporting unprecedented load growth and California's long-term transmission needs. We respectfully request that CAISO:

1. Explicitly evaluate Viridon's proposed alternatives in the 2025-26 TPP
2. Compare these solutions against longer-term projects on a benefit-cost basis
3. Recognize the unique value of solutions deployable faster than greenfield projects
4. Consider how near-term upgrades can complement and accelerate benefits of long-term projects.

Viridon’s analysis demonstrates that these cost-effective upgrade solutions offer significant capital and grid operating cost savings, with benefits measurable in the hundreds of millions to billions of dollars annually. Beyond congestion cost savings, Viridon's proposed upgrades can materially increase Path 15 transfer capability, particularly when deployed as part of a coordinated set of corridor reinforcements.

The exceptional congestion levels on Path 15, combined with unprecedented load growth and resource development patterns, demand immediate action. Viridon's solutions offer a path forward that is technically feasible, economically beneficial, and rapidly deployable.

[1] Page 198 of the 2025-2026 Transmission Planning Process Policy and Economic Preliminary Assessment and Study Updates - Nov 19, 2025.

[2] Id at 203.

[3] Page 2 of PG&E’s 2025 Request Window Proposals presentation – September 25, 2025.

[4] Page 9 of PG&E’s 2024 Fourth Quarter and Full Year Earnings presentation – February 13, 2025.

[5] November 2025 Preliminary Assessment, p. 198 and 203; and CAISO 2024-2025 Transmission Planning Process (“TPP”) Policy and Economic Preliminary Assessment and Study Updates presented on November 13, 2024, p. 26 and p. 43.

[6] Viridon conducted PCM using Hitachi's Gridview simulation tool. The LMP spread between PG&E Bay Area and the SCE Area is projected to be ~$17/MWh (annual average) in 2039 based on Viridon’s PCM using the 2024-25 TPP economic case. The LMP spread for the 2035 Base Portfolio is measured to be ~$50/MWh based on Viridon’s preliminary PCM using the 2025-26 TPP preliminary case.

[7] Feb 20, 2025 Decision p. 60 and Final Compact -Dashboard_25-26TPP_BaseCaseD_2025-02-20 (See for example workbook sheet “Summary_byRESOLVE_area” showing significantly increased solar mapping to southern PGAE relative to RESOLVE optimized build, and see sheet “2035_Criteria_Alignment” indicating for example, that SCE northern solar resources and East of Pisgah Mohave solar resources were “Shifted to North of Path 26 for improve reliability…”)

[8] See CPUC Final Compact-Dashboard_25-26TPP_BaseCaseD_2025-02-20, sheet “PreviousTPP_Summary_byArea” for the 2025-26 TPP Portfolio

[9] Page 105 of the IRP Workshop for 2025 Inputs and Assumptions presentation – February 27, 2025.

[10] CPUC Base Case Results Viewer spread sheet posted October 2025, Transmission sheet, showing forward and reverse flows on the various tranches of upgrades defined by the CPUC.

[11] From CPUC-issued RESOLVE Results Viewers, Transmission sheet showing selected tranches and timing.

[12] CPUC staff response to question during November 12, 2025 IRP Webinar on the Proposed 2026-27 Transmission Planning Process Portfolios and Preliminary Busbar Mapping Results, p. 4.

[13] Per GO 131-E, “installing new mid-line series capacitors on a transmission or power line to support an increase in the power transfer capability” is categorized as an “upgrade” and does not require a CPCN: “An extension, expansion, upgrade, or other modification to an electric public utility’s existing electrical transmission facilities, including electric transmission lines, substations, and switchyards within existing transmission easements, rights of way, or franchise agreements, irrespective of whether the electrical transmission facility is above a 200 kV voltage level”.

[14] Upgrades to PG&E’s end terminals would also be required.

[15] Institute of Electrical and Electronics Engineers’ paper “SSR Implication Assessment Using Modular FACTS”: SSR Implication Assessment Using Modular FACTS | IEEE Conference Publication | IEEE Xplore

[16] 00_CAISO_PreliminaryPCM_BasePortfolio_2035_NovSH case from the Economic Planning Study materials posted November?24,?2025; Viridon refined a single N-2 contingency definition to accurately capture binding constraints along the Path 15 corridor. CAISO has indicated these preliminary cases will continue to be updated through the planning cycle.

[17] The SmartValve power flow control solution is not directly included in the analysis because the modeling methodology still needs validation in Gridview. Viridon stands ready to support CAISO’s assessment of this technology in collaboration with the technology provider.

[18] Studied a new Los Banos – Tracy 500 kV line incrementally to the LBG3 upgrades and new Gates – Midway.

[19] Based on 2035 Base portfolio preliminary PCM results shown in the previous section for solution A, 45% multiplied by $1.2 billion in annual total congestion cost reduction multiplied by 5 years.

[20] Based on the CAISO 2025-26 TPP 2040 Winter Peak PG&E Bulk reliability case and 2040 Summer Peak case, without double-line outages. Each run compares a pre-project baseline to a post-upgrade scenario.

[21] Viridon conducted a RESOLVE simulation using the proposed RESOLVE base case and removing RESOLVE’s ability to trigger the Path15/26 upgrades, and compared the NPV of Total Resource Costs from the CPUC’s Results viewer Dashboard sheet using the CPUC-proposed Delayed Off-Shore Wind Base Case Scenario with that of a comparable RESOLVE run but with the Path 15/26 upgrades disabled. The NPV of Total Resource Costs without the ability to upgrade Paths 15 and 26 was $2.895 billion than the case in which the upgrades were enabled and triggered by RESOLVE.

[22] Id., Curtailment results from RESOLVE’s Results Viewer Generation & Loads sheets, row 121 for each respective cases.

[23] Viridon conducted a RESOLVE simulation using the proposed RESOLVE base case and a modified base case wherein the first tranche of Path 15/26 upgrades was made available starting in 2030 and at a cost of approximately two times the estimated cost of Viridon’s most quickly deployable LBG3 upgrade solution. (Twice the cost was used in recognition that the tranche also represents an upgrade to Path 26, and Viridon roughly assumed twice the cost to include comparable upgrades to Path 26). The NPV of Total Resource Costs between the RESOLVE base case simulation and the revised tranche 1 case was $927 million as indicated by comparing Resource NPVs from respective Results Viewer Dashboard sheets, and the revised tranche 1 case Results Viewer Transmission sheet shows a selection of the modified tranche 1 in the first run year in which the upgrade is made available.

[24] Based on Viridon’s PCM with 24-25 TPP cases.

[25] CPUC Base Case Results Viewer spread sheet posted October 2025, Transmission sheet, showing forward and reverse flows on the various tranches of upgrades defined by the CPUC.

[26] [26] Id.

[27] In accordance with the increased bi-directional flows and as indicated by the reduced curtailment referenced in Section 3 of the Quantified Benefits presented above.

8. Please provide your organization’s comments on the Testing Results of Congestion Revenue Allocation

9. Please provide any additional comments on the November 19, 2025 Transmission Planning Process Stakeholder Meeting