Comments on Intertie Schedule Modeling Enhancements (8/24)

1. Please provide your organization’s perspective on the Intertie Schedule Modeling Enhancements stakeholder workshop presentation on August 24, 2026.

No comments.

2. Please provide your organization’s perspective on enhancing the modeling of intertie schedules on CAISO interties to improve accuracy of congestion management and representation of effects of these schedules under the GAP-Tie design as described in the workshop presentation.

No comments.

3. Please provide your organization’s perspective on the price formation impacts on modeling intertie schedules under the GAP-Tie design as described in the workshop presentation.

No comments.

4. Please provide your organization’s perspective on the Resource Adequacy (RA) imports process, including RA reassignment processes, as described in the workshop presentation.

CDWR’s current interest is understanding the specific roles and responsibilities of each party involved. It will be helpful for CAISO to provide examples that clearly identify the parties involved and describe their respective responsibilities, roles, and privileges. For example, when an RA import occurs: how many potential scheduling coordinators could there be, and what are their roles?

To illustrate, CDWR found the material that explicitly stated the RAAIM responsibility started at the import resource SC but migrated to the generation resource after reassignment to be particularly valuable. Similar language describing which SC is responsible for submitting TSR’s, E-tags, as well as which SC is responsible for RA replacement and outages, would be greatly appreciated.

In addition, phasing out CAISO EDAM internal interties, specifically the change from energy schedules at the intertie to submitting energy schedules at the physical generator and load resources with concurrent TSR submission, represents a significant change to the operational procedures of how CDWR operates with its counterparts.

Therefore, we request CAISO to clarity and provide detailed examples illustrating scheduling coordinator roles for each of the following: for  TSR submission, load, generator, import resource, export resource, E-tag submission, RA showing, RA reassignment, RA acceptance, would be helpful as these changes may necessitate renegotiating of the existing contract to provide power and RA capacity.

In the CAISO/EDAM scenario, what happens if reassignment does not occur (slide 29)? What specific penalties and obligations would remain? And are they the responsibility of the LSE SC? Or the import resource SC?

In the CAISO/EIM scenario, can CDWR or any other load serving entity serve as the import resource scheduling coordinator? If yes, how does this work? The GAP-tie model includes the RA providing generating resource as part of the model, but at the same time, CDWR wouldn’t have direct control over the generating resource.

5. Please provide your organization’s perspective on the examples shared illustrating different intertie scheduling scenarios, including varying the location of the intertie schedule and the source of the supporting generation, and the resulting expectations for delivery and settlement across the day-ahead and real-time markets, as described in the workshop presentation. Are there variations to these examples, different scenarios, or additional elements that would support further understanding?

We believe that two major topics have not been adequately addressed in the scenarios discussed:

1. Roles and responsibilities of transacting parties and scheduling coordinators involved
2. How bids and energy transfers in the GAP-tie models transition from the Day-Ahead market into the HASP and Real Time markets, and specifically how imbalance energy is handled.

1. Roles and Responsibilities

It would be helpful for the next workshop to cover specific  roles and responsibilities of all parties involved, and what (TSR’s, energy schedules, E-tags) needs to be submitted, and to whom (CAISO, WEIM BAA, EDAM BAA).  How many potential scheduling coordinators may be involved in an energy transfer? And which BAA would they belong to: CAISO? Or the external BAA?

First, in the case of an EDAM import into CAISO, such as an import from PacifiCorp into CAISO for example, how many participants are there and who does what? We would like to see breakdowns such as:

Masterfile Registrations

1. SC1: registers import transfer resource, ITR1 in CAISO
2. SC1: registers import TSR1 at ITR1 in CAISO
3. SC2: registers export transfer resource ETR1 in Pacificorp
4. SC2: registers export TSR2 at ETR1 in Pacificorp

Before Trade Date

5. How do we identify PSE to submit E-tag?
6. SC1 submits TSR1 for trade date and import to CAISO
7. SC2 submits TSR2 for trade date and export to Pacificorp
8. SC3 submits energy schedule at load to CAISO
9. SC4 submits energy schedule at generator to Pacificorp

Second, in the case of CAISO to non-EDAM BAA import or export . We understand the situation is different, where energy schedules are submitted at the DGAP instead of the SP-tie, but now that the generation resource is included in the model, CWDR has similar questions about roles and responsibilities:

• Does the import SC need to have control of the generation resource?
• If not, and the import SC submits an energy schedule at the DGAP,
  • What happens if the physical generation doesn’t generate?
  • Who is responsible for outages? Import SC or Generation Resource SC?
  • Is this handled on Pacificorp’s side or CAISO’s side?

2. Real-Time Market Transition

Within the real-time market, it is not clear how imbalance energy is handled in EDAM/CAISO imports and exports. We can foresee 3 sets of data that need to be updated as the market transitions across time from Day Ahead to HASP to Real Time:

• TSR – Do TSR’s need to get submitted for as energy deviates in HASP and RT? If yes? By whom and to which BAA?
• E-Tags – Do Etags need to get submitted as energy deviates? If yes? By Whom and to which BAA?
• Generator Schedules – Generators can participate in the RT market. Are they responsible for communicating updated schedules to the import/export SCs?
• Load Schedules – Loads don’t participate in the RT market. How are their deviations handled in TSR’s and E-Tags?

Related, how does the energy stack work when it comes to energy transfers? Does the entirety of an energy schedule need to transfer across the intertie?

• If Yes, how is imbalance energy handled?
  • How is it handled in CAISO/EDAM?
  • How is it handled in CAISO/EIM?
• If No,
  • How is the proportion of energy transferred calculated? CAISO/BAA follow the TSR?
  • If the energy generated is insufficient to meet the TSR quantity, what happens?
    • How is Handled in CAISO/EDAM?
    • How is it handled in CAISO/EIM?

6. Please provide your organization’s perspective on the concept of phasing out intertie scheduling at CAISO EDAM internal interties (interties between the CAISO and an EDAM balancing area), and associated challenges of supporting EDAM transfers and intertie schedules at the same intertie locations, as described in the workshop presentation.

During the initial EDAM implementation, CAISO established a transitional measure allowing market participants to continue bidding standard imports, specifically for RA resources at what are now internal EDAM transfer locations. Phasing out intertie scheduling at internal EDAM interties fundamentally changes how imported energy and RA capacity must be delivered and accounted for.

We would like some clarity on CAISO’s plans for how things will be handled when additional BAA’s join the EDAM. Will this transition period be repeated with Portland General Electric, BANC, and LADWP when they become EDAM entities? Will there be concurrent and SP-Tie and GAP-tie as there is today with Pacificorp? If not, what option will there be to test out and prepare for the new intertie transitions?

Additionally, the impacts on the real-time market are not as clear. It looks like CAISO will use Real-Time transfer to mirror the RA import Day-Ahead schedules into CAISO BAA and settle the RA imports at Default GAP-Tie. CAISO needs to provide details of analysis and impacts on generic financial or physical portfolio import bids based on its proposal. 

7. Please provide your organization’s perspective on the impacts on commercial arrangements of phasing out intertie scheduling at CAISO EDAM internal interties, as well as potential ways or steps to mitigate any potential adverse impacts. Please be as specific as possible in identifying commercial or other impacts, and potential mitigations to address or minimize those impacts.

Phasing out CAISO EDAM internal interties, specifically the change from energy schedules at the intertie to submitting energy schedules at the physical generator and load resources with concurrent TSR submission, represents a significant change to the operational procedures of how CDWR operates, specifically with LADWP.

Clarity on who should be the scheduling coordinator for each role: TSR submission, load, generator, import resource, export resource, E-tag submission, RA showing, RA reassignment, RA acceptance, would be helpful as these changes may necessitate renegotiating of the existing contract to provide power and RA capacity.

CDWR needs to be able to fully understand the implications of who does what, what additional responsibilities and privileges each role provides, to be able to enter contract negotiation.

8. Please provide your organization’s perspective on any other aspects of the August 24, 2026 workshop.

Please update the SIBR manual to include documentation on how TSR’s imports and exports should be operating in the production environment. 

Pacificorp and CAISO are already EDAM entities and should have been transacting using the new TSR systems. Real world examples, if available, would be of appreciated.

In the case of CAISO to EIM-Non-EDAM BAA imports and exports, what is the specific plan for the turnover going from SP-Ties to GAP-ties? CDWR can envision a few possible scenarios:

• Something like the concurrent transition period occurs where both SP-ties and GAP-ties are available to transact.
• A hard cut-off scenario, where SP-Ties are disabled and GAP-ties are enabled at the same time.
  • In this situation, CDWR would want to have all the GAP-ties pre-registered before the flip occurs and testing in MAP-stage completed to test transactions.

1. Please provide your organization’s perspective on the Intertie Schedule Modeling Enhancements stakeholder workshop presentation on August 24, 2026.

Comments on the Intertie Schedule Modeling Evolution Stakeholder

Workshop – August 24, 2026

Department of Market Monitoring

September 8, 2026

Summary

The Department of Market Monitoring (DMM) appreciates the opportunity to comment on the August 24, 2026 Intertie Schedule Modeling Enhancements Stakeholder Workshop.[1] Given the limited time the ISO allocated in the workshop to discuss the topic of economic bidding at internal extended day-ahead market (EDAM) interties, it is not clear to DMM what issues are preventing economic bidding at internal EDAM interties. DMM believes the ISO needs to dedicate further time to this issue in the next workshop.

Because there is currently no economic bidding at non-CAISO EDAM balancing authority area (BAA) interties, not allowing economic bidding at CAISO’s internal EDAM interties would reduce access to CAISO markets for parties outside EDAM submitting price sensitive bids. Therefore, understanding what issues could prevent bidding at internal EDAM interties, and potential solutions to overcome these issues, should be an important topic of discussion in this stakeholder process.

Comments

Relationship between bidding at non-CAISO EDAM BAA interties and CAISO internal EDAM interties  

If economic bidding were allowed at non-CAISO EDAM BAA boundary interties, then there would seem to be little point to having economic bidding at CAISO internal EDAM interties. An importer could bid at the EDAM boundary intertie, clear economically, and get the price at this intertie. If they were to instead bid at the CAISO internal EDAM intertie, they would still have to wheel through the non-CAISO EDAM BAA. These imports would be settled based on the boundary intertie price minus the CAISO internal EDAM intertie price plus the CAISO internal EDAM intertie price — so that the net payment of these imports at the CAISO internal EDAM interties would be the same as if they had bid at the non-CAISO EDAM BAA boundary tie. In either case, the EDAM optimization would determine whether the import supplied load in the CAISO or non-CAISO BAA and determine transfers accordingly.

However, non-CAISO EDAM entities do not currently allow economic bidding at non-CAISO EDAM interties. Without economic bidding at the internal EDAM interties with CAISO, market participants will lose the ability to access this intertie capacity to participate in the ISO markets with economic bids. Thus, market participants sourcing power from outside EDAM who, before EDAM, may have wheeled across a non-CAISO EDAM BAA to reach the CAISO internal EDAM intertie, are currently limited to self-scheduling at the border of the non-CAISO EDAM BAA. The power would then either supply the non-CAISO EDAM BAA or facilitate EDAM transfers to CAISO or another non-CAISO EDAM BAA. Because this supply is limited to self-scheduling, this reduces competition for supply in the CAISO market and may limit market efficiency since this additional supply is unable to clear based on economic bids aligned with their cost. Economically bid exports are also similarly affected.

The ISO needs to clarify the double counting revenue balance issues

In the stakeholder workshop, ISO staff expressed concern of potential double counting of supply if a non-resource specific import at a CAISO internal EDAM intertie were to end up sourcing power from a generator in a non-CAISO EDAM BAA that has a day-ahead energy schedule.

DMM does not currently understand the potential issue raised by the ISO. To source the power from a generator in an EDAM BAA after the day-ahead market, the importer would also need to export the energy from the EDAM BAA in the real-time markets — i.e., they would have to buy power at the real-time price. This export would need to be served by incremental real-time supply in the EDAM BAA, which could come from some other supply source if the specific generator cannot provide incremental energy.[2] This appears to DMM to be very similar to standard real-time market incremental schedules. The export settlement would provide payment to whomever provided the incremental real-time energy schedule supporting the export. Therefore, there would not be an energy revenue imbalance created by this transaction. This transaction should also not cause a real-time congestion revenue shortfall because these shortfalls are caused by real-time net reductions in settled flows on binding constraints, and not incremental real-time schedules.[3]

The ISO should clarify the potential issues with imports at internal EDAM interties potentially sourcing power from resources inside EDAM BAAs so that the ISO can work with stakeholders on potential ways to overcome these issues. Specifically, DMM asks the ISO to clarify:

• What specific issues are these schedules creating?
• Why are these issues not a concern for imports at CAISO external interties to non-EDAM BAAs that might end up sourcing from a generator in an EDAM BAA?
• If the problem is with imports sourced from generators in an EDAM BAA, why should this also restrict imports/exports sourced/sunk in non-EDAM BAAs?

The ISO needs to clarify how uncleared import bids would reduce transfer capacity

DMM would also like clarification on how import bids that do not clear the market would reduce transfer capacity. It seems feasible to model a constraint that the net transfers plus net imports are less than or equal to the available capacity at the intertie. In this case imports would not reduce capacity available for transfers unless it was lower cost to clear the imports than clear the transfers. This is similar to how the ISO explained the modeling works for the external EDAM intertie at Malin.[4] 

Conclusion

DMM looks forward to further clarification and discussion of these issues with the ISO and stakeholders in upcoming workshops. 

[1]  Intertie Schedule Modeling Enhancements - Stakeholder Workshop, California ISO, August 24, 2026: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Intertie-Schedule-Modeling-Enhancements-Aug-24-2026.pdf

[2]  This could also be a reduction in consumption from other day-ahead load or export schedules.

[3]  Where payments to schedules reducing flows are not offset by payments from schedules increasing flows.

[4]  Day-Ahead Market Enhancements: Configurable Parameters Implementation Working Group Session #5, California ISO, November 20, 2025, p 45: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Day-Ahead-Market-Enhancements-Configurable-Parameters-Implementation-Working-Group-Nov-20-2025.pdf

2. Please provide your organization’s perspective on enhancing the modeling of intertie schedules on CAISO interties to improve accuracy of congestion management and representation of effects of these schedules under the GAP-Tie design as described in the workshop presentation.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

3. Please provide your organization’s perspective on the price formation impacts on modeling intertie schedules under the GAP-Tie design as described in the workshop presentation.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

4. Please provide your organization’s perspective on the Resource Adequacy (RA) imports process, including RA reassignment processes, as described in the workshop presentation.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

5. Please provide your organization’s perspective on the examples shared illustrating different intertie scheduling scenarios, including varying the location of the intertie schedule and the source of the supporting generation, and the resulting expectations for delivery and settlement across the day-ahead and real-time markets, as described in the workshop presentation. Are there variations to these examples, different scenarios, or additional elements that would support further understanding?

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

6. Please provide your organization’s perspective on the concept of phasing out intertie scheduling at CAISO EDAM internal interties (interties between the CAISO and an EDAM balancing area), and associated challenges of supporting EDAM transfers and intertie schedules at the same intertie locations, as described in the workshop presentation.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

7. Please provide your organization’s perspective on the impacts on commercial arrangements of phasing out intertie scheduling at CAISO EDAM internal interties, as well as potential ways or steps to mitigate any potential adverse impacts. Please be as specific as possible in identifying commercial or other impacts, and potential mitigations to address or minimize those impacts.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

8. Please provide your organization’s perspective on any other aspects of the August 24, 2026 workshop.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

1. Please provide your organization’s perspective on the Intertie Schedule Modeling Enhancements stakeholder workshop presentation on August 24, 2026.

• The GAP-Tie model represents a limited improvement for non-source specific RA imports compared to the current SP-Tie model.
• PG&E reiterates its request for a full and detailed walkthrough of the life of an RA import from cradle to grave (see Question #4).
• PG&E seeks clarification on:
  • How would price formation work at an intertie with multiple BAAs at a single tie point under the GAP-Tie model?
  • Is CAISO going to have multiple scheduling points at the same intertie?
  • Does CAISO plan to model injections at an EDAM BAA’s external border as part of its total DGAP?

2. Please provide your organization’s perspective on enhancing the modeling of intertie schedules on CAISO interties to improve accuracy of congestion management and representation of effects of these schedules under the GAP-Tie design as described in the workshop presentation.

The GAP-Tie model represents a limited improvement for non-source specific RA imports compared to the current SP-Tie model. CAISO’s description of the GAP-Tie methodology as creating a weighted average location for the generation coming from the source BA represents an improvement compared to the current SP-Tie design that models a fictitious generator directly on the other side of each CAISO intertie.

3. Please provide your organization’s perspective on the price formation impacts on modeling intertie schedules under the GAP-Tie design as described in the workshop presentation.

PG&E seeks clarification on:

• How would price formation work at an intertie with multiple BAAs at a single tie point under the GAP-Tie model?
• Is CAISO going to have multiple scheduling points at the same intertie?
  • CAISO appeared to suggest in the workshop there could be multiple prices at one tie point (e.g., Malin).
  • Alternatively did CAISO mean there would be one price at Malin, the BPA Default Generation Aggregation Point (DGAP)? If so then would a transfer from PacifiCorp West be coming in across a different intertie?
• Does CAISO plan to model injections at an EDAM BAA’s external border as part of its total DGAP?
  • Does CAISO plan to develop a new DGAP model each time a wheelthrough RA import contract is signed?

4. Please provide your organization’s perspective on the Resource Adequacy (RA) imports process, including RA reassignment processes, as described in the workshop presentation.

At this time PG&E does not foresee a problem with the reassignment process, but does reiterate its request that CAISO provide a full and detailed walkthrough of the life of an RA import from cradle to grave, including the CAISO monthly showing, reassignment, bidding, scheduling, tagging, potential substitution (if needed), real-time scheduling, and finally settlement. And then show how the reassignment process would impact that flow. The examples that CAISO provided at the 8/24 workshop were not well designed to assist stakeholders in fully thinking through potential issues.

5. Please provide your organization’s perspective on the examples shared illustrating different intertie scheduling scenarios, including varying the location of the intertie schedule and the source of the supporting generation, and the resulting expectations for delivery and settlement across the day-ahead and real-time markets, as described in the workshop presentation. Are there variations to these examples, different scenarios, or additional elements that would support further understanding?

See previous comment.

6. Please provide your organization’s perspective on the concept of phasing out intertie scheduling at CAISO EDAM internal interties (interties between the CAISO and an EDAM balancing area), and associated challenges of supporting EDAM transfers and intertie schedules at the same intertie locations, as described in the workshop presentation.

PG&E understands that this is necessary to support the EDAM design.

7. Please provide your organization’s perspective on the impacts on commercial arrangements of phasing out intertie scheduling at CAISO EDAM internal interties, as well as potential ways or steps to mitigate any potential adverse impacts. Please be as specific as possible in identifying commercial or other impacts, and potential mitigations to address or minimize those impacts.

PG&E will continue to evaluate any implications of these changes to our commercial arrangements. At this time, PG&E has not identified any critical issues.

8. Please provide your organization’s perspective on any other aspects of the August 24, 2026 workshop.

No comments.

1. Please provide your organization’s perspective on the Intertie Schedule Modeling Enhancements stakeholder workshop presentation on August 24, 2026.

PacifiCorp appreciates CAISO's presentation during the August 24, 2026, stakeholder meeting. At this time, PacifiCorp believes additional stakeholder discussion is warranted before CAISO moves forward with transitioning from the current intertie scheduling framework to a GAP-Tie construct. The stakeholder discussions highlighted a continued need for additional information and analysis before implementing a significant market design change. While CAISO has identified potential benefits associated with a GAP-Tie framework, stakeholders have raised questions regarding the economic and reliability advantages of the proposal, as well as the continued reliance on modeling assumptions for price formation and source attribution. PacifiCorp appreciates CAISO's commitment to publish a comparative analysis and believes this information will help stakeholders better understand the differences between the current scheduling-point methodology and the proposed GAP-Tie approach. 

The CAISO indicated a desire to phase out intertie schedules at import EDAM internal interties, citing that the transitional design is temporary and contributes to increased transmission conformance, double counting of supply, and inefficient use of transmission. PacifiCorp requests that CAISO present quantitative information at a future stakeholder meeting regarding the frequency and market impacts of transmission conformance and double counting of supply. PacifiCorp also believes the cited transmission inefficiencies primarily affect the day-ahead market, as the transmission capacity is still available for transfers in the real-time market.  

The proposed phase-out of intertie schedules on EDAM internal interties, including MDWP, appears to create unnecessary restrictions on bilateral transactions. PacifiCorp is particularly concerned about potential stranded-load scenarios in which load relies on firm transmission service into CRAG. Limiting the use of existing transmission paths could diminish the value of long-term transmission investments and may require the use of alternative scheduling routes that depend on less-certain transmission availability. PacifiCorp encourages CAISO to further evaluate these edge cases and discuss potential alternatives that preserve operational flexibility while addressing objectives sought. 

While CAISO suggested that participants could instead schedule across EDAM external interties, the practicality of that approach may be more limited than anticipated. As the EDAM footprint expands, restricting the use of certain intertie paths could create unintended congestion on neighboring transmission systems. Market participants may be required to secure additional transmission service, which may only be available on a non-firm basis, in order to serve load. Furthermore, during transmission outages or derates, a single transmission path may be the only viable option for meeting contractual obligations. PacifiCorp requests additional discussion at a future stakeholder meeting regarding alternative approaches and the potential impacts of the proposal on both import and export scheduling. 

2. Please provide your organization’s perspective on enhancing the modeling of intertie schedules on CAISO interties to improve accuracy of congestion management and representation of effects of these schedules under the GAP-Tie design as described in the workshop presentation.

PacifiCorp understands CAISO's preference to move toward a GAP-Tie design, as it is intended to more closely align day-ahead schedules with power flows observed in the real-time market. Throughout the stakeholder process, participants have raised concerns regarding significant business practice changes, resource adequacy delivery implications, multiple locational marginal prices (LMP) at a single intertie location, congestion revenue rights auction impacts, and effects on contractual arrangements. While CAISO has worked to address these issues during stakeholder discussions, additional dialogue is warranted given the magnitude of changing a fundamental market design element that affects transactions at CAISO interties. 

The CAISO has addressed concerns regarding multiple prices at a single intertie location by proposing the use of Default GAP (DGAP) pricing from an adjacent balancing authority (BA). The CAISO acknowledged that this approach is not a perfect solution but stated that it better reflects market conditions than the current use of a "fictional generator" at a scheduling point. During the presentation, CAISO also noted that "operators may need to take additional action to conform transmission elements in the day-ahead market with expected real-time flows." PacifiCorp requests that CAISO provide information on the frequency, magnitude, and market impacts of these transmission conformance actions so stakeholders can better understand the scope of the issue the proposal is intended to address and evaluate whether the proposed design changes are commensurate with the problem being solved.

3. Please provide your organization’s perspective on the price formation impacts on modeling intertie schedules under the GAP-Tie design as described in the workshop presentation.

The examples presented at the workshop demonstrate the MCC and MCL component of the LMP are impacted which at a glance are understood. The comparative analysis of the LMPs at various intertie locations under the current modeling design and the proposed GAP-Tie design will allow for robust discussion on the impacts of GAP-Tie LMP pricing. PacifiCorp looks forward to continued dialogue and further understanding of the benefits of GAP-Tie implementation. 

4. Please provide your organization’s perspective on the Resource Adequacy (RA) imports process, including RA reassignment processes, as described in the workshop presentation.

No comment.

5. Please provide your organization’s perspective on the examples shared illustrating different intertie scheduling scenarios, including varying the location of the intertie schedule and the source of the supporting generation, and the resulting expectations for delivery and settlement across the day-ahead and real-time markets, as described in the workshop presentation. Are there variations to these examples, different scenarios, or additional elements that would support further understanding?

No comment.

6. Please provide your organization’s perspective on the concept of phasing out intertie scheduling at CAISO EDAM internal interties (interties between the CAISO and an EDAM balancing area), and associated challenges of supporting EDAM transfers and intertie schedules at the same intertie locations, as described in the workshop presentation.

As an EDAM Balancing Authority and a load serving entity, PacifiCorp understands the changes with phasing out EDAM internal intertie schedules to limit Type 1 schedules at MDWP and CRAG, leaving Type 2 and Type 4 available from transmission customers and the Entity respectively. PacifiCorp requests confirmation on this understanding as it believes this change would create undue restrictions at intertie locations that are frequently bilaterally transacted at. Several load serving entities in PacifiCorp utilize bilateral interchange transactions to meet their resource sufficiency requirements and secure supply, so eliminating this ability at CAISO EDAM internal interties may disrupt their trading practices.  

Additionally, PacifiCorp has load which utilizes CRAG and would otherwise be stranded during outage conditions without the ability to use Type 1 to serve. PacifiCorp requests the CAISO to discuss the handling of this edge case. As the EDAM footprint grows, there will be other locations frequently bilaterally transacted on that are impacted by this change which need to be considered prior to this policy change. PacifiCorp would like confirmation on whether this phasing out is limited to transfer locations between the CISO EDAM BA and EDAM BAAs or whether this change is also EDAM BAA to EDAM BAA (i.e., PacifiCorp and Portland General Electric). PacifiCorp requests the CAISO to address this understanding and the implications described in a future stakeholder call.

7. Please provide your organization’s perspective on the impacts on commercial arrangements of phasing out intertie scheduling at CAISO EDAM internal interties, as well as potential ways or steps to mitigate any potential adverse impacts. Please be as specific as possible in identifying commercial or other impacts, and potential mitigations to address or minimize those impacts.

As referenced in question 6, edge cases of stranded load need to be considered. There are only so many transmission paths for utilities to schedule energy on. If those transmission paths are limited from market participation, firm rights that have been invested in will lose value and adverse effects would arise due to different scheduling routes utilized on non-firm transmission. PacifiCorp understands that Type 2 could be released but the likelihood of it being awarded is not concrete which is a large impact on load service that needs to be considered.   

Additionally, this proposal may require changes to PacifiCorp’s Tariff attachment T sections 4.1 and 4.3.1 and the impact on the EDAM RSE, other post day ahead sufficiency tests and PacifiCorp transmission customer donations to the market are all not fully flushed out with the phasing out of this design. These changes will have an unknown/unexplained impact on PacifiCorp’s transmission customers and load serving entities by changing the workflow of bilaterial transactions, trading and tagging in the region. Further, this phasing out would restrict PacifiCorp transmission customers that aren't scheduling coordinators and have no desire to become one from transacting with PacifiCorp.

8. Please provide your organization’s perspective on any other aspects of the August 24, 2026 workshop.

No comment.

1. Please provide your organization’s perspective on the Intertie Schedule Modeling Enhancements stakeholder workshop presentation on August 24, 2026.

Comments of Powerex Corp. on

Intertie Schedule Modeling Enhancements

August 24, 2026 Stakeholder Meeting

Powerex appreciates the opportunity to submit comments on the California ISO’s August 24, 2026 meeting on the Intertie Schedule Modeling Enhancements stakeholder process. 

Topic 1 – Proposal to Replace Modeling of Intertie Bids as Injections at CAISO Boundary with Modeling as Aggregate Generation in Adjacent BAA

The meeting focused primarily on the California ISO’s proposal to replace the current representation of intertie bids as generation located at the boundary tie point with a representation of intertie bids as the aggregate generation sources of a balancing authority area (BAA) on the “other side” of that boundary tie point. 

Powerex appreciates that the California ISO’s rules regarding intertie bidding lead to specific challenges.  Namely, intertie bids can be submitted as “system resources,” and are not required to identify a specific generating resource or even a BAA that is the source of the imported electricity. The California ISO has also repeatedly declined to require intertie bids that receive a day-ahead market award to submit an e-Tag on a day-ahead basis, meaning that the source of intertie imports may remain unknown even through the real-time market.  Given these rules, assumptions are made regarding how to represent the generation of electricity—and the resulting flows on the grid—associated with a cleared intertie bid. 

The GAP-Tie Proposal Should Not Move Forward Until Analysis Clearly Indicates That a Material Problem Exists, and that the Proposal Would Lead to Significant Improvements

Currently, the California ISO models an intertie import as a generator located at the specific intertie.  The California ISO’s presentation explained that this representation can be inaccurate, and described some of the implications that could occur as a result.  However, no comprehensive analysis has been provided on the actual frequency, magnitude, or consequences of the current approach.  It is therefore not yet clear whether the current SP-Tie representation is leading to material adverse consequences for reliability, efficiency or pricing accuracy. 

The California ISO is proposing to replace the existing SP-Tie representation (as generation at an intertie) with a different representation (as aggregated generation in an adjacent BAA).  This representation will also be inaccurate; it will even apply to imports offered by Scheduling Coordinators that have no connection to the adjacent BAA where the source is assumed to be. How inaccurate this assumption will be, or how frequently, is unclear, as there has been no analysis presented on the anticipated outcomes under the GAP-Tie approach, including whether accuracy may actually decline in certain circumstances. 

Any change to the representation of how supply flows on the California ISO grid has the potential to have significant impacts on which resources clear the market and the prices determined in that market.  Such changes should only be considered after a careful analysis showing that the existing approach leads to material challenges, and that an alternative approach has been identified that leads to significantly improved outcomes.  Until then, it is unclear whether the benefits of replacing one assumption with a different assumption warrants dedicating limited California ISO and stakeholder resources, given the several other initiatives that are underway. Powerex appreciates that California ISO staff have indicated that an analysis is already in progress, and looks forward to continued engagement on this topic.

The GAP-Tie Proposal Would Be Patently Inaccurate for Imports on DC Interties

Imports delivered on Direct Current (DC) interties, including deliveries to NOB using the Pacific DC Intertie (PDCI), pose a unique circumstance that is not properly addressed under the GAP-Tie framework.  DC interties are controllable devices: the scheduled quantities determine the electricity physically injected into the grid at the terminal.  This makes them different from imports scheduled to AC interties, where the electricity flows are primarily determined by the location of generation and load in the interconnected grid, and are generally not impacted by the choice of delivery point. 

It would be highly inaccurate and inappropriate to represent deliveries at NOB as injections in Bonneville’s BAA.  In the absence of a binding scheduling limit, such a representation would mean that electricity imports at Malin receive the same price as electricity imports at NOB, even under conditions where the California ISO needs electricity delivered to its SP15 region (as occurs with imports at NOB) more than to its NP15 region (as occurs with imports at Malin).

The California ISO’s own indicative data shows this problem clearly.  The table below shows the marginal cost of congestion (MCC) component for deliveries at Malin and at NOB in the Fifteen Minute Market for August 26, 2026 HE22.  The left-hand columns show the MCC under the current SP-Tie methodology, while the right-hand columns show the MCC under the indicative GAP-Tie combinations:

Under the current SP-Tie approach, deliveries on the PDCI to NOB were recognized as providing roughly $1,000/MWh more value to the California ISO than deliveries at Malin.  OASIS data confirms that the scheduling limits were not binding at either location; the entire MCC difference was due to internal physical flow congestion (largely across Path 15).  Under the proposed GAP-Tie approach, however, this difference in value would be entirely eliminated.  This is because deliveries at NOB would be modeled identically to deliveries at Malin; as injections in Bonneville’s BAA.  Both deliveries are therefore modeled as having the same flow impact on constraints in the California ISO.  The flows on the California ISO grid resulting from the two deliveries are unambiguously not the same.

Powerex requests that the California ISO provide a detailed description and discussion regarding how it intends to model deliveries on DC interties, and to fully account for the significantly different circumstance that such deliveries present compared to deliveries scheduled on AC interties.

Greater Clarity is Needed Regarding Proposed Changes and Impacts to CRRs

At the August 24 workshop, the California ISO explained that its GAP-Tie proposal would have implications for CRRs.  The discussion with stakeholders indicated the need for greater clarity on the extent of these implications, and the anticipated changes that the California ISO intends to pursue.  In particular, there appears to be a need for greater clarity regarding the following topics:

1. Whether the GAP-Tie proposal would create new congestion exposure between locations that are currently not covered by existing CRRs;
2. Whether existing CRRs sourcing or sinking at an intertie are moved to the adjacent DGAP or whether new CRRs will be required from adjacent DGAP to the intertie.
3. Will the DGAPs and interties be biddable locations in future the CRR Auctions.

Topic 2: Eliminating Day-Ahead Intertie Bidding at CAISO Interties with Other EDAM Entities

The August 24 workshop briefly introduced the California ISO’s second proposal, which is to eliminate intertie bidding at “EDAM Internal Interties,” referring to the interties between the California ISO and a BAA participating in EDAM.  This proposal raises significant concerns, and Powerex believes that the California ISO should reconsider this proposal until such time as it can be undertaken without causing significant loss of economic supply participation for the California ISO and for the EDAM area.

Intertie bidding has been the principal mechanism through which supply located outside of the California ISO participates in the day-ahead market.  This supply is extensive, at times exceeding 9,000 MW or more of imports into the California ISO BAA.  In addition, this includes a substantial amount of clean, carbon-free supply including supply from hydro resources in the Northwest.  The ability of the California ISO to access supply from a range of different geographic areas also provides it with resource diversity, tapping into sources of supply from parts of the West that may not be experiencing the same conditions or challenges as the California ISO.

With the launch of EDAM, it would perhaps be understandable that the California ISO would seek to encourage or even require supply that is located in EDAM BAAs to participate in the day-ahead market directly—by economically bidding or scheduling the output of specific generation resources—rather than by offering that supply through the intertie bidding framework.  But the California ISO’s proposal is far broader than that, and would eliminate intertie bidding at all EDAM internal interties, even for entities delivering supply from a BAA that does not—and may not ever—participate in EDAM.

Under the California ISO’s proposal, the day-ahead market (including both the California ISO and other EDAM BAAs) would lose access to price-responsive external supply offered under the intertie bidding framework.  To date, no EDAM entity has indicated that it will enable intertie bidding at its external interties.  This means that external supply will no longer be able to be economically offered, and will instead need to be scheduled in fixed quantities, driven largely by the expectation of its value in EDAM.  This undermines the often-expressed desire to encourage participation with economic offers rather than through self-schedules.  By requiring suppliers to commit to a quantity without knowing the market price, such transactions will now entail significantly greater price risk, which can be expected to reduce the quantity and increase the price of external supply that is made available.  It is also not clear whether EDAM entities will support self-scheduling of external supply into their BAAs, to be settled directly through EDAM, or whether external supply will need to be transacted bilaterally with a customer inside the BAA.  This could introduce yet another source of inefficiency and friction in accessing external supply.

Moving forward with the California ISO’s proposal at this time would be a major step backward for all involved, reducing the California ISO’s (and EDAM’s) access to external supply, and restricting market access for entities that do not wish to join EDAM. 

If the California ISO seeks to eliminate intertie bidding from its EDAM internal interties, Powerex believes it must first ensure that there is a fully comparable intertie bidding framework in place at all EDAM external interties.  This includes not only requiring all EDAM entities to enable intertie bidding on their external interties.  It also requires EDAM to adopt and implement a durable framework to allocate congestion value to firm OATT transmission service.  This is because “pushing out” the location of intertie bidding can change the prices that external supply is paid, reflecting the cost of congestion between the “old” and “new” intertie bidding locations.  This congestion-related value currently is received by entities that use firm OATT transmission service to physically deliver to the California ISO boundary, and the California ISO’s proposal should not be bundled with an attempt to shift how this value is allocated.  The California ISO and stakeholders are currently grappling with this issue in the EDAM Congestion Revenue Allocation stakeholder process, and many of the same principles are relevant here.

Given that there is no comparable intertie bidding opportunity available to replace the intertie bidding options that the California ISO is proposing to eliminate, Powerex strongly recommends that this proposal be withdrawn.  If the California ISO wishes to encourage supply located in an EDAM BAA to participate by submitting generator offers rather than through intertie bids, a proposal more narrowly tailored to that specific goal could be explored.

2. Please provide your organization’s perspective on enhancing the modeling of intertie schedules on CAISO interties to improve accuracy of congestion management and representation of effects of these schedules under the GAP-Tie design as described in the workshop presentation.

Please see  Powerex comments CAISO intertie schedule modeling enhancements.pdf

3. Please provide your organization’s perspective on the price formation impacts on modeling intertie schedules under the GAP-Tie design as described in the workshop presentation.

Please see  Powerex comments CAISO intertie schedule modeling enhancements.pdf

4. Please provide your organization’s perspective on the Resource Adequacy (RA) imports process, including RA reassignment processes, as described in the workshop presentation.

Please see  Powerex comments CAISO intertie schedule modeling enhancements.pdf

5. Please provide your organization’s perspective on the examples shared illustrating different intertie scheduling scenarios, including varying the location of the intertie schedule and the source of the supporting generation, and the resulting expectations for delivery and settlement across the day-ahead and real-time markets, as described in the workshop presentation. Are there variations to these examples, different scenarios, or additional elements that would support further understanding?

Please see  Powerex comments CAISO intertie schedule modeling enhancements.pdf

6. Please provide your organization’s perspective on the concept of phasing out intertie scheduling at CAISO EDAM internal interties (interties between the CAISO and an EDAM balancing area), and associated challenges of supporting EDAM transfers and intertie schedules at the same intertie locations, as described in the workshop presentation.

Please see  Powerex comments CAISO intertie schedule modeling enhancements.pdf

7. Please provide your organization’s perspective on the impacts on commercial arrangements of phasing out intertie scheduling at CAISO EDAM internal interties, as well as potential ways or steps to mitigate any potential adverse impacts. Please be as specific as possible in identifying commercial or other impacts, and potential mitigations to address or minimize those impacts.

Please see  Powerex comments CAISO intertie schedule modeling enhancements.pdf

8. Please provide your organization’s perspective on any other aspects of the August 24, 2026 workshop.

Please see  Powerex comments CAISO intertie schedule modeling enhancements.pdf

1. Please provide your organization’s perspective on the Intertie Schedule Modeling Enhancements stakeholder workshop presentation on August 24, 2026.

TransAlta Energy Marketing U.S. (TEMUS) appreciates the opportunity to comment on the August 24, 2026 Intertie Schedule Modeling Enhancements Stakeholder Workshop. During the workshop the CAISO presented the total elimination of economic bidding at internal CAISO/EDAM interties as un fait accompli: however, GAP-Tie modeling and eliminating internal-intertie bidding are separate design choices and should be approached as such.

TEMUS supports congestion modeling improvements and aligning day-ahead market assumptions with anticipated physical flows. However, the changes proposed under this initiative are substantial and will have a significant impact on price formation, commercial transactions, the value of OATT-based transmission rights, and import volumes.

TEMUS recommends preceding under these principles:

1. Preservation of economic bidding;
2. Recognition of  external firm transmission;
3. Protect existing CRRs, and;
4. Require quantitative evidence before adopting GAP-Tie or eliminating internal-intertie bidding.

2. Please provide your organization’s perspective on enhancing the modeling of intertie schedules on CAISO interties to improve accuracy of congestion management and representation of effects of these schedules under the GAP-Tie design as described in the workshop presentation.

While TEMUS appreciates that the GAP-Tie design will improve modeling results, the CAISO has not yet presented evidence that this will improve market efficiency or modeling accuracy enough to justify the potentially negative commercial impacts.

In addition, a broadly averaged distribution may differ significantly from actual operating patterns in particular hours. While CAISO’s single-hour Malin example showed relatively small differences, one hour is not sufficient to determine materiality. TEMUS suggests that volatility and tail-hour exposure may matter more than average differences.

Before transitioning away from the SP-tie design, the CAISO should demonstrate how the proposed GAP distribution is materially more accurate and does not introduce new systematic error, by intertie and under stressed system conditions.

In addition, TEMUS echoes requests from other stakeholders that future workshops provide more detail and examples of how this change will impact current commercial practices, including:

• Detailed bid-to-bill examples;
• Settlement examples;
• Resource adequacy examples, and;
• LMP comparisons between current and GAP-Tie designs.

3. Please provide your organization’s perspective on the price formation impacts on modeling intertie schedules under the GAP-Tie design as described in the workshop presentation.

TEMUS supports maintaining one transparent LMP for each defined intertie location. This will increase market transparency and efficiency.

However, under the GAP-tie design even with one LMP for each intertie there may be a wide range of congestion exposure that is difficult to estimate ahead of the day-ahead market deadline. In future workshops TEMUS would like to better understand the impact of the GAP-tie design on price formation, including:

• How frequently the GAP distribution would change;
• Whether it would be seasonal or static;
• How market participants would receive notice;
• Whether historical price relationships could change through administrative updates, and;
• How stakeholders could validate the assumptions.

In addition to the impact on price formation under the GAP-tie design, there are important price formation impacts resulting from the removing economic bidding at CAISO EDAM internal interties. This change significantly weakens price formation and drastically Increases the incentive to self-schedule upstream.

4. Please provide your organization’s perspective on the Resource Adequacy (RA) imports process, including RA reassignment processes, as described in the workshop presentation.

TEMUS would appreciate additional clarification as to how Maximum Import Capability (MIC) deliverability within CAISO and OATT transmission rights would meld for RA resources contracted to California loads. TEMUS’ understanding from the August 24^th meeting is that MIC is required but not evidence of upstream firm transmission.

In addition, TEMUS would be interested in the answers to the questions that Southern California Edison (SCE) raised during the workshop:

• What prevents the underlying EDAM generator from bidding at a high cap where the original import was subject to different RA import bidding rules?
• Which party bears the GHG obligation?
• Must delivery occur over the same intertie for which import capability was secured?
• How would price-correction rules apply?
• What would a complete bid-to-bill example show?

5. Please provide your organization’s perspective on the examples shared illustrating different intertie scheduling scenarios, including varying the location of the intertie schedule and the source of the supporting generation, and the resulting expectations for delivery and settlement across the day-ahead and real-time markets, as described in the workshop presentation. Are there variations to these examples, different scenarios, or additional elements that would support further understanding?

TEMUS appreciated the additional detail in the scheduling and settlement examples presented at the August 24^th meeting. However, these examples were “high-level”, and it would be helpful for the CAISO to expand the scope to include:

• Who receives each payment;
• How the transaction settles when awards and tags differ;
• How upstream transmission is reflected;
• What happens under negative prices or outages;
• How congestion rights perform, and;
• What changes when economic bidding is unavailable.

6. Please provide your organization’s perspective on the concept of phasing out intertie scheduling at CAISO EDAM internal interties (interties between the CAISO and an EDAM balancing area), and associated challenges of supporting EDAM transfers and intertie schedules at the same intertie locations, as described in the workshop presentation.

TEMUS does not support phasing out intertie scheduling at CAISO-EDAM internal interties unless CAISO first establishes a functionally equivalent economic-bidding option and demonstrates that the alternative preserves access, delivery flexibility, and congestion-hedging opportunities.

TEMUS understands CAISO’s concerns that direct bids at an EDAM internal intertie may create a risk of double counting where the same physical EDAM generation is also offered at its resource node and may reserve transfer capability that could otherwise be used by EDAM optimization. Those concerns should be addressed through targeted design rules – such as making unused transmission from external supply bids available for EDAM optimization once the bid does not clear or the scheduling deadline has passed - rather than by broadly eliminating intertie scheduling.

In addition, the elimination of economic bidding raises important questions not addressed in the workshop regarding transfer capability and scheduling rights and whether they become subordinated to EDAM optimization, especially since CAISO itself noted in the meeting that a market dominated by self-schedules may have to curtail self-schedules to achieve feasibility.

7. Please provide your organization’s perspective on the impacts on commercial arrangements of phasing out intertie scheduling at CAISO EDAM internal interties, as well as potential ways or steps to mitigate any potential adverse impacts. Please be as specific as possible in identifying commercial or other impacts, and potential mitigations to address or minimize those impacts.

The elimination of internal-intertie bidding could materially change the economics and operability of existing transactions. Many arrangements were negotiated based on elements such as the availability of a named CAISO delivery point, the ability to submit an economic bid at that point, established SP-Tie price history, specified transmission paths, allocation of market revenues, and defined day-ahead and real-time obligations.

TEMUS needs to better understand how curtailment would be operationalized for EDAM transfers after the elimination of intertie bidding to suggest how hedging might be modified in commercial arrangements.

8. Please provide your organization’s perspective on any other aspects of the August 24, 2026 workshop.

TEMUS appreciates CAISO’s intention to better understand the commercial impacts of this proposal in greater detail. TEMUS looks forward to reviewing the comparative LMP analysis that the CAISO committed to during the workshop, as well as more detailed scenario materials.

TransAlta also encourages CAISO to coordinate this initiative with the EDAM Congestion Revenue Allocation and the CRR Enhancement initiatives. Decisions regarding GAP-Tie pricing, transfer locations, CRR eligibility, OATT transmission rights, transfer revenue, and congestion-revenue allocation are economically interdependent.

TEMUS cannot support phasing out CAISO-EDAM internal-intertie bidding if the practical result is to replace economic offers from non-EDAM supply with self-schedules at upstream EDAM external interties, or to strand or materially devalue firm transmission and congestion hedges.

1. Please provide your organization’s perspective on the Intertie Schedule Modeling Enhancements stakeholder workshop presentation on August 24, 2026.

WPTF appreciates the opportunity to comment on the Aug 24 workshop. WPTF does not support moving to the GAP-Tie design unless and until the CAISO demonstrates that the change is expected to benefit the overall market. A potential improvement in one aspect of power-flow modeling is not, by itself, a sufficient basis to select a design that also changes bidding opportunities, unit commitment and dispatch, price formation, congestion management, and existing commercial arrangements.

The CAISO should establish whether GAP-Tie modeling actually produces more accurate modeled flows across a representative range of transactions. The proposal replaces the SP-Tie assumption that imports are injected directly at the boundary with an adjacent-area DGAP assumption, and replacing one assumption with another does not necessarily make the resulting power-flow representation more accurate because not all energy importing at one location may be sourced from generation within the adjacent BAA.

Second, even if power flow modeling improves in some circumstances, the CAISO should demonstrate that the net effect provides improved market efficiency. WPTF has repeatedly requested discussion of how this policy will increase self-scheduling, which in turn degrades efficient unit commitment and dispatch decisions, leading to inefficient price formation and congestion management. Those issues remain largely unaddressed and should be discussed and evaluated before the CAISO identifies a preferred design. CAISO continues to discuss price formation and improved benefits solely from a power-flow perspective.

2. Please provide your organization’s perspective on enhancing the modeling of intertie schedules on CAISO interties to improve accuracy of congestion management and representation of effects of these schedules under the GAP-Tie design as described in the workshop presentation.

The GAP-Tie design may improve power-flow representation for transactions that are actually supplied by generation in the balancing authority area adjacent to the intertie. However, improved power-flow representation does not translate into improved congestion management which relies on economic offers and accurate price formation.

Regarding improved power flow modeling; the CAISO has not yet demonstrated that GAP-Tie modeling is more accurate across the broader range of intertie transactions. The proposed design replaces the current assumption that an import is injected at the intertie with a different assumption that it is sourced from aggregate generation in the adjacent balancing authority area. That may be a different representation, but not necessarily a better one. It may be less representative for imports sourced in a non-adjacent area, wheeled through the adjacent area, or supported by generation in another adjacent BAA. The relevant modeling question is therefore not simply whether GAP-Tie is theoretically more consistent, but how often and by how much it more accurately represents expected flows than the current approach.

Regarding improved congestion management; even if the power flow representation is improved (i.e., the shift factors generated from the power-flow model more accurately represent where the actual energy is flowing) that does not mean improved accuracy of congestion management. For congestion management to be efficient, it relies on first having an optimal and efficient set of unit commitment and dispatch decisions made by the market optimization. The CAISO first runs the market optimizer using all offers submitted to determine unit commitment and dispatch. This is then fed into the power-flow model. If the first step (i.e., market optimization output) is inefficient, then the power-flow will also be inefficient/inaccurate.

Moving to the GAP-Tie design as proposed by the CAISO also includes reduced economic offers and increased self-scheduling of imports. Whenever there is an increase in self-scheduling this, by definition, degrades the market’s ability to determine the true least cost and optimal set of resources to commit and dispatch. It then follows that if the unit commitment and dispatch are suboptimal, the ability for the market to efficiently manage congestion is also degraded because it relies on the economic offers to determine how to most efficiently manage the congestion. This is true even if the new assumptions for the energy importing from an adjacent BAA is more accurate than injection right at the border because the power-flow model is first fed an inefficient unit commitment and dispatched set of resources due to the increased self-schedules. Improved power-flow modeling, even if demonstrated, does not necessarily mean improved market efficiency or customer benefits.

3. Please provide your organization’s perspective on the price formation impacts on modeling intertie schedules under the GAP-Tie design as described in the workshop presentation.

WPTF understands that the basic LMP calculation would not change under the GAP-Tie design and WPTF continues to support a single, transparent price for a given product at each intertie location. We agree that mathematically nothing significant will change. We will likely see changes in congestion and loss components due to the change in assumption as to where the energy is sourcing from. However, our main concern with price formation from this proposal has to do with the fact that it will increase self-scheduling and dilute the overall accuracy of price signals which are needed to ensure optimal unit commitment, dispatch decisions, and congestion management.

From the power flow perspective; while mathematically nothing really changes, the “improved” prices CAISO notes this policy will generate is only from the power-flow perspective and only occurs if the new assumption of where the energy is sourcing from is a more accurate assumption that injecting at the intertie today. While we don’t disagree that for some of the imports, the new assumption will be more accurate than assuming it’s injected directly at the boundary, not all energy will actually come from the neighboring BAA it’s assumed to come from. So, the real question is – how much more accurate in aggregate is this assumption compared to the status quo? If energy is assumed to come from one BAA but comes from another, is this actually worse off than assuming its injected at the intertie location.

From a market efficiency perspective; as noted in response to #2, the impact on price formation from this policy is ignoring a significant change – the increase in self-schedules that this policy introduces. WPTF has previously asked the CAISO to evaluate the market-efficiency consequences of the broader design, including the potential increase in self-scheduling as discussed in response to Question 6. Those consequences have not yet been meaningfully addressed. Even if GAP-Tie shift factors improve the representation of some schedules, increased self-scheduling can make market prices less reflective of marginal production costs and reduce the market's ability to make efficient unit commitment, dispatch, and congestion-management decisions. Please see response to question #6 below for more detailed discussion.

4. Please provide your organization’s perspective on the Resource Adequacy (RA) imports process, including RA reassignment processes, as described in the workshop presentation.

No comment at this time.

5. Please provide your organization’s perspective on the examples shared illustrating different intertie scheduling scenarios, including varying the location of the intertie schedule and the source of the supporting generation, and the resulting expectations for delivery and settlement across the day-ahead and real-time markets, as described in the workshop presentation. Are there variations to these examples, different scenarios, or additional elements that would support further understanding?

No comment at this time.

6. Please provide your organization’s perspective on the concept of phasing out intertie scheduling at CAISO EDAM internal interties (interties between the CAISO and an EDAM balancing area), and associated challenges of supporting EDAM transfers and intertie schedules at the same intertie locations, as described in the workshop presentation.

WPTF remains concerned that phasing out intertie scheduling at CAISO EDAM internal interties could materially increase self-scheduling. If market participants can no longer submit economic bids at the intertie where energy is currently delivered to the CAISO, transactions sourced outside the EDAM footprint will need to be self-scheduled at an upstream EDAM external intertie to preserve delivery to the CAISO.

As WPTF noted in prior comments, increased self-scheduling can adversely affect market efficiency. A self-schedule reduces the market’s visibility of the marginal cost of all available supply and generally must be accommodated by the market without being economically compared with other available supply. As a result, the market will be forced to take a self-scheduled import rather than commit or dispatch a potentially lower-cost resource. This is turn also creates prices that do not truly represent the marginal cost of energy at that location; which is a fundamental benefit of having a nodal market. In other words, higher levels of self-scheduling create less meaningful prices for the market to use to make unit commitment and dispatch decisions and for congestion management, resulting in suboptimal and inefficient overall market outcomes.

Increased self-scheduling could also reduce the flexibility available to manage congestion and make market prices less reflective of underlying marginal costs. With fewer economic bids available for redispatch, the market will have fewer options to resolve congestion at least cost. Thus, even if GAP-Tie modeling provides a more accurate representation of the physical impacts of certain schedules, the broader design could still produce less efficient commitment, dispatch, congestion-management, and price-formation outcomes.

Even if the CAISO demonstrates that GAP-Tie improves power-flow modeling in certain circumstances, that finding alone would not demonstrate an improvement in overall market efficiency.

7. Please provide your organization’s perspective on the impacts on commercial arrangements of phasing out intertie scheduling at CAISO EDAM internal interties, as well as potential ways or steps to mitigate any potential adverse impacts. Please be as specific as possible in identifying commercial or other impacts, and potential mitigations to address or minimize those impacts.

WPTF would appreciate it if the CAISO can provide more details regarding how it plans to transition the CRR source/sink locations under a GAP-Tie design, if ultimately adopted. We recall when this was originally being discussed the CAISO understood the concern that changing CRR definitions and nodal prices used to settle the CRRs mid-year creates misalignment and can disrupt the CRR market. We feel it would be best that any changes made to the available source/sink nodes and the prices at which those CRRs clear are done in concert and at the beginning of the year. 

8. Please provide your organization’s perspective on any other aspects of the August 24, 2026 workshop.

WPTF recalls that the CAISO had previously made available the definitions of the new GAP-Tie locations and has posted historical prices for participants to get an idea of how they differ from the existing SP-Tie prices and definitions. We respectfully request that the CAISO re-issue the GAP-Tie definition document and also show where on OASIS the historical GAP-Tie prices are located such that participants are able to access that information.