Comments on Straw Proposal for Uplift, Default Energy Outage Management, State of Charge and Stakeholder Discussion from July 22, 2026

Storage design and modeling

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Comment period
Jul 21, 08:00 am - Aug 05, 05:00 pm
Submitting organizations
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ACP-California
Submitted 08/05/2026, 02:47 pm

Submitted on behalf of
ACP-California

Contact

Caitlin Liotiris (ccollins@energystrat.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

ACP-California appreciates the CAISO’s continued efforts to improve storage design and modeling through this initiative. As discussed more below, we generally support the proposals put forward for storage and hydro Default Energy Bids (DEBs) in the July 2026 Revised Straw Proposal. However, at this time, ACP-California does not support continued development of the new NGR bidding concept. Based on what has been presented to date, we do not believe this concept will provide enough benefits to warrant further development, especially given the complexities it would introduce and remaining unanswered questions about how it would interact with other programs or elements of the market. Therefore, we recommend that CAISO focus on other topics in this initiative and delay further consideration of the new NGR bidding concept for the time being.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

ACP-California does not have substantive comments on the timeline, except to emphasize that – at this juncture – the NGR bidding concept is not ready to proceed towards a subsequent proposal.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

ACP-California supports continued development of the storage DEB using a time-of-day (TOD) approach and directionally supports the proposal put forward at the July 22nd meeting. Specifically, in the latest proposal, we appreciate that CAISO has moved away from utilizing TOD multipliers below 1.0 and has simplified the overall design of the TOD DEBs.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

CAISO should continue to pursue the latest TOD approach to DEB for storage, which is preferable to a static approach. The TOD approach is preferable given that the opportunity costs for storage resources vary across hours of the day and the TOD DEBs can best reflect this reality.   

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

ACP-California generally supports the proposed direction for hybrid DEBs, under which hybrids would be subject to the “greater of” the DEBs for their underlying components.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

ACP-California recognizes it may be reasonable to require a minimum share (e.g., 10%) of the underlying technology type in order to apply the higher DEB of the underlying components. However, we caution CAISO that setting a “greater of” threshold that is too low could cause DEBs to be set below the resource’s opportunity costs. It would be helpful to review the current set of hybrid resource configurations to determine if there are hybrids with very small shares of one high-cost component. This analysis could also help inform what a reasonable threshold for the “higher of” DEB treatment may be.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

CAISO has proposed a new approach for storage bidding where typical interval-by-interval bidding would be replaced by a bid to deviate from end-of-horizon state-of-charge. While we appreciate CAISO exploring this option, we are concerned that continued development and exploration could distract from work to finalize storage and hybrid DEBs and may also distract from consideration and development of other important market enhancements.

At this juncture, ACP-California is unconvinced that a fundamental restructuring of how storage resources interact with the market is necessary. And ACP-California is concerned the proposed new NGR bidding concept would effectively remove the ability for storage operators to control the charging/discharging of their resources and reduce or eliminate the ability to strategically bid in each interval. Additionally, the implementation of this new bidding approach raises a host of questions about how it would interact with other programs and products and how it would reflect some of the operational realities of batteries.

Notably, battery storage resources have cycle count limits which, if not adhered to, can result in degradation of the battery and impact asset life. However, it is not clear how a Scheduling Coordinator for a storage resource could express the maximum daily cycles they are willing to accept under the new NGR bidding structure. If storage resources are unable to control the number of cycles they are undertaking per day, it could impact asset life and lead to real costs for battery storage operators. If this new bidding concept were to proceed, CAISO would need to develop a mechanism to permit cycle count constraints to be communicated to the market operator.

ACP-California also has significant questions about how this bidding concept would interact with elements of the Resource Adequacy (RA) program – including must-offer obligations and RAAIM – as well as with ancillary service awards. It is unclear how a storage resource would meet its must offer obligations under this new bidding paradigm or how it would be assessed RAAIM penalties. CAISO would also need to provide more information on how ancillary service awards would interact with the end of horizon bidding concept.

Given all of these uncertainties and the likely significant implementation lift to develop this new bidding concept, ACP-California does not support additional development of this concept at this time. If CAISO, nevertheless, continues to pursue it, at a minimum, CAISO should more clearly explain the expected advantages, as well as the anticipated implementation lift and how CAISO anticipates the concept would interact with key programs and requirements (including those outlined above).

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

AES
Submitted 08/05/2026, 05:35 pm

Contact

Rahul Kalaskar (rahul.kalaskar@aes.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

AES appreciates the opportunity to comment on the July 22, 2026 discussion of the Storage Design and Modeling – Uplift, Default Energy Bids, and State-of-Charge Management Straw Proposal. AES supports the direction of the revised storage default energy bid (DEB) proposal and continues to believe that near-term enhancements to the storage DEB, together with development of real-time make-whole mechanisms, should proceed before the ISO undertakes broader changes to day-ahead bid cost recovery or the uplift framework. This sequencing reduces the risk that uplift reforms are built on top of a DEB and modeling foundation that itself still needs correction. AES continues to support pausing day-ahead bid cost recovery changes until this broader framework has been established. With respect to the end-of-horizon state-of-charge bidding reframing concept, AES believes the concept is intriguing but not yet ripe for endorsement; additional quantitative analysis is needed before stakeholders can meaningfully evaluate its tradeoffs.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

AES generally supports the proposed near-term timeline. AES encourages the ISO to adhere to the sequencing reflected in that timeline—advancing storage DEB enhancements and real-time make-whole mechanisms ahead of day-ahead bid cost recovery redesign—rather than compressing these steps to meet a fixed date. If new information from the SOC bidding reframing discussion or from real-time make-whole design suggests that additional time is warranted for any single work stream, AES encourages the ISO to adjust the schedule for that work stream rather than allow schedule pressure to shortcut analysis.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

AES supports the proposal to scale price-based opportunity costs upward based on historical hourly LMP comparisons between markets over the prior three days, and supports applying a 1.4 multiplier to price-based opportunity costs in both the day-ahead and real-time markets to bring the storage DEB into closer alignment with the hydro DEB. AES agrees this improves consistency across resource types subject to local market power mitigation. AES requests that the ISO clarify which components of the revised calculation — including the multiplier itself — will be codified in the tariff versus addressed in the Business Practice Manual, since BPM treatment would allow future refinement as empirical data accumulates without requiring a FERC filing. AES also asks the ISO to confirm how the highest-discharge-hour and lowest-price-hour selection will be applied consistently across storage durations.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

AES appreciates the data the ISO presented comparing the static and time-of-day approaches and is open to either construct provided the underlying pricing input accurately reflects systematic price separation between markets. AES asks the ISO to evaluate whether a resource's LMP, its DGAP, or the relevant CAISO Trading Hub price produces the most representative scalar for non-WEIM-only storage resources, since a resource that has recently been mitigated may show a smaller historical price separation than the broader market. The ISO should ensure the pricing input cannot be understated simply because a resource's own recent prices were themselves suppressed by mitigation.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

Consistent with comments AES has provided earlier in this initiative, AES supports development of a dedicated hybrid DEB methodology that reflects the characteristics of a hybrid resource's underlying components. AES supports further development of the greater-of approach as a practical near-term solution, paired with a minimum share requirement to prevent a small component from setting the DEB for the entire hybrid resource, as illustrated by the ISO's example of a 1 MW storage component setting the DEB for a 100 MW hybrid facility.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

AES recommends the ISO set the minimum share requirement using an empirical review of the current hybrid resource fleet's component mix, calibrated so that the requirement addresses the market power mitigation concern the ISO identified without inadvertently excluding a meaningful share of existing hybrid configurations from the greater-of approach. AES is willing to work with the ISO and other stakeholders on the appropriate percentage once fleet composition data is shared.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

AES is skeptical that the end-of-horizon state-of-charge bidding reframing concept is ready to advance at this time and believes further analysis is needed before the ISO or stakeholders can evaluate it on the merits. As the ISO itself notes, embedding opportunity costs beyond the optimization horizon into a single terminal value would require corresponding changes to how other state-of-charge constraints are modeled — including the ancillary services state-of-charge (ASSOC) constraint and the day-ahead market enhancements (DAME) envelope constraints — and to how attenuation factors for regulation, imbalance reserves, and reliability capacity affect opportunity costs across products in the same settlement interval. AES requests that the ISO first develop quantitative examples or simulation results showing how this reframing would perform against today's framework under a range of price and dispatch conditions before stakeholders are asked to weigh in substantively. AES also has concern that price formation under the CAISO proposal, which optimally manages state of charge, will be even less intuitive compared to the current NGR model, which dispatches storage resources based on the price-quantity pair with implicit opportunity costs. 

 

Given AES's broader position that DEB enhancements and real-time make-whole mechanisms should be completed before other structural changes proceed, AES also recommends the ISO treat this reframing concept as a longer-term work stream rather than allow it to compete for near-term prioritization against the DEB and uplift sequencing already underway.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

California Community Choice Association
Submitted 08/05/2026, 03:05 pm

Contact

Shawn-Dai Linderman (shawndai@cal-cca.org)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

The California Community Choice Association (CalCCA) appreciates the opportunity to comment on the Storage Design and Modeling Straw Proposal. In summary, the CAISO should:  

  • Continue development of a “time-of-day” storage default energy bid (DEB) that better reflects storage resource costs when real-time conditions deviate from day-ahead conditions and changes in opportunity costs throughout the day;
  • Adopt the “greater-of” DEB methodology for hybrid resources with a variable generation component;
  • Consider whether a different DEB approach for hybrid resources with gas generation is necessary to ensure market power cannot be exerted; and
  • If the CAISO continues to explore reframing non-generator resource (NGR) bidding, do so only as an additional option that scheduling coordinators (SC) can elect to use, not a mandatory change.
2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

CalCCA has no comments at this time.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

CalCCA supports modifying the storage DEB to vary by the time of day. This approach will better reflect storage resources’ costs when real-time conditions deviate from day-ahead conditions and better reflect how storage resources’ opportunity costs change throughout the day. The CAISO should continue to pursue the time-of-day approach rather than the static-value approach.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

See comments in Section 3 above.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

CalCCA supports developing a DEB for hybrid resources. When the generating component is a variable resource, the CAISO’s proposed solution of taking the greater of the DEBs for the individual components will likely effectively ensure that the hybrid resource cannot exercise market power, as it is very unlikely a zero marginal cost resource will withhold from the market. However, this does not hold true when the generation component is dispatchable (e.g., gas). For example, in the CAISO’s example on Slide 40,[1] in which the hybrid resource’s variable cost is $35 per megawatt hours (MWh) and the storage DEB is $25 per MWh, the greater-of approach could result in economic withholding of the storage component through bids up to $10 higher than the storage DEB. The CAISO should therefore consider whether a different approach for hybrid resources with gas generation is necessary to ensure market power cannot be exerted.  

 


[1]            https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Jul-22-2026.pdf.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

CalCCA understands the CAISO’s desire for a minimum share requirement so that suppliers are not incentivized to configure their resources in a manner that would prevent the CAISO from properly applying market power mitigation (e.g., the edge case of a 100 MW hybrid resource made up of 99 megawatts (MW) of solar and 1 MW of battery storage). To determine how to set the minimum share, the CAISO should first evaluate existing hybrid resource configurations established prior to the issuance of the hybrid DEB proposals to evaluate how resources were configured absent this policy. The CAISO could then set the requirement in line with how existing resources are configured and apply it going forward for future hybrid configurations.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

CalCCA appreciates the CAISO’s desire to more efficiently incorporate the future value of stored energy into storage bidding. However, reframing non-generator resource bidding as described in the Straw Proposal could negatively impact SCs’ ability to manage their resources in other ways. For example, SCs can use multi-segment bid curves to manage grid charging restrictions and shape day-ahead schedules. The ability to do so would be reduced should NGR bidding be reframed in the manner described in the Straw Proposal.

If the CAISO continues to explore reframing NGR bidding in this manner, the CAISO should do so only as an additional option for bidding that SC can elect to use, not a mandatory change. This way, SCs can continue to manage their resources using the existing NGR bidding framework if desired.  

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

CalCCA has no additional comments at this time.

California Energy Storage Alliance (CESA)
Submitted 08/05/2026, 03:45 pm

Contact

Donald Tretheway (donald.tretheway@gdsassociates.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

The California Energy Storage Alliance (CESA) appreciates the opportunity to comment on the July 22, 2026 discussion of the Storage Design and Modeling – Uplift, Default Energy Bids, and State-Of-Charge Management Straw Proposal.  The proposed storage DEB has made significant improvement from prior proposals. CESA requests CAISO determine which components of the revised storage DEB calculation will be included in the tariff and which will be included in the business practice manual (BPM). Over time empirical analysis may support modification of individual multipliers in order to continue to meet the storage DEB guiding principles.  By including the multipliers in the BPM, CAISO could modify, through a stakeholder process to review the empirical analysis, without the need for a FERC filing.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

CESA is supportive of the proposed timeline.  CESA believes that the revised storage DEB can be brought for WEM Governing Body decision before the end of the year.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

Scaling Price-Based Opportunity Costs

CESA supports scaling opportunity costs, upward only, based upon historical comparisons of the hourly LMPs from the prior three days between markets. This change includes near-term systematic price differences between markets in the storage DEB.  This change aligns with the current negotiated option for WEIM-only storage resources. 

CESA requests CAISO confirmation that the opportunity cost will still be based upon the lowest price hour in the highest discharge hours covering the storage duration of the battery.  For example, the 4th highest price in the day-ahead market would be used for a 4-hour battery.

Apply a 1.4 Multiplier to Opportunity Cost

CESA supports applying a 1.4 multiplier to price-based opportunity costs in both the day-ahead and real-time market to further consistency with the hydro DEB.  Based upon discussion at the meeting, CESA supports extending the hydro multiplier to the storage DEB.  CESA understands that CAISO believes this is appropriate because the analysis supporting the hydro DEB development sought to limit hydro dispatch to no more that 4 hours of dispatch in the real-time market in greater than 90% of the days.  Thus, this analysis could equally be applied to a 4-hour battery. 

Apply 1.4 Time-of-Day Multiplier in Real-Time DEB

CESA supports applying a 1.4 multiplier to the real-time DEB in the hours before the hour that set the price-based opportunity cost and 1.0 multiplier after the hour that set the price-based opportunity cost.  This will reduce the probability that a mitigated discharge bid will prematurely deplete the state-of-charge before it is needed for the real-time net load peak.

Include the Gas Floor from the Hydro DEB

CESA supports including the gas floor from the hydro DEB in both the day-ahead and real-time DEB which will help correctly position storage resources in the bid stack when mitigated. 

Removal of Energy Cost

With the inclusion of the gas floor, CESA supports removing the energy cost from the storage DEB calculation while retaining variable operations and maintenance (VOM) costs. 

Charging DEB equals Discharging DEB less VOM costs

CESA supports setting the charging DEB equal to the discharging DEB less VOM costs.  CESA supports the 2026 Variable Operations and Maintenance Cost Review proposal to change the default VOM included in the storage DEB from $0.00/MWh to $14.74/MWh.  This change will ensure that mitigated storage resource have monotonically increasing bids from the charge to discharge.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

CESA believes the static approach could include a scaling approach similar to the time-of-day proposal to recognize changing system conditions.  Likewise, the use of system prices could be included in the time-of-day approach.

The CAISO presented data comparing the static proposal and the time-of-day proposal. CESA requests CAISO analyze if using a resource’s LMP or its relevant DGAP or CAISO Trading Hub for non-WEIM-only storage resource would more accurately reflect system price differences between markets more accurately.  CESA notes that using a DGAP or CAISO Trading Hub would be consistent with the concept of the competitive LMP used in mitigation.  If a CAISO Trading Hub had 20% historical price separation, but an individual resource saw a lower price separation because it had been mitigated the past three days, the aggregate pricing of the CAISO Trading Hub may be a better representation of changing system conditions between markets.  Thus, the scalar could be set at the higher of the CAISO Trading Hub based scalar or the resource’s LMP based scalar.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

CESA supports calculating the DEB for hybrid resources using the highest technology type of DEB for resources within the aggregation.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

CESA believes that the percentage constraint within the calculation should be set by looking at existing hybrid resources.  The percentage should be set at a level that would allow all existing hybrid resources to use the higher-of DEB proposal.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

CESA believes this warrants additional discussion as storage becomes the marginal resource in the market. Reframing non-generator resource bidding, while potentially beneficial and needed, will require significant time investment.  The reframing will require a holistic review of all storage modeling constraints and price formation objectives.

In particular, CESA seeks greater clarity on whether and the extent to which other storage constraints will be impacted. Modifying how end-of-horizon opportunity costs are included in the market optimization will require changes to how other state-of-charge constraints are modeled.  For example, the ancillary services state-of-charge (ASSOC) constraint and the day-ahead market enhancements (DAME) envelope constraints.  The use of attenuation factors for regulation, imbalance reserves, and reliability capacity will further change how opportunity costs between products in the same settlement interval are determined.

Further, CESA recommends careful prioritization with competing storage efforts through the remainder of the year so as not to complete storage design changes that can be implemented in the near term.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

No additional comments

California ISO - Department of Market Monitoring
Submitted 08/05/2026, 03:49 pm

Contact

Aprille Girardot (agirardot@caiso.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

Comments on Storage Design and Modeling: Straw Proposal on

Default Energy Bids, Uplift, and State-of-Charge Management

Department of Market Monitoring

August 5, 2026

Summary

The Department of Market Monitoring (DMM) appreciates the opportunity to comment on the Storage Design and Modeling: Straw Proposal on Default Energy Bids, Uplift, and State-of-Charge Management issued July 15, 2026.[1] While DMM supports some aspects of the ISO’s storage default energy bid (DEB) proposal, we have several significant concerns with the proposed design. The proposed storage DEB will significantly overstate the marginal cost of storage resources in nearly all instances. The proposed storage DEB does not appear to have been developed with the intent of accurately estimating marginal cost, and is instead designed to set DEBs for batteries at a higher level than DEBs for energy limited hydro resources.

DMM recommends that the ISO continue developing the time-of-day approach for storage default energy bids rather than the static approach, as the time-of-day framework can be designed to more accurately reflect the location-specific and time-varying opportunity costs of storage resources. However, DMM recommends that the time-of-day multiplier includes values below one to more accurately reflect falling opportunity costs during highest-priced hours. DMM also recommends that the ISO either remove the price-based opportunity cost multiplier entirely, or at most retain its current value of 1.1 rather than increase it to 1.4, as proposed. This recommendation is particularly important if the ISO continues to limit the time-of-day multiplier to values at or above one.

DMM continues to oppose inclusion of the gas floor in the storage DEB calculation. The gas floor is not related to the marginal costs of storage resources, and DMM does not agree that DEB design should be used to establish an a priori preferred dispatch order among resource types. DEBs should be designed to estimate marginal costs of each resource as accurately as possible, rather than to establish a preferred relative position of resources in the bid stack. Dispatch is most efficient when based on the actual marginal costs of each resource type.

More broadly, DMM encourages the ISO to ensure that the storage DEB remains grounded in a reasonable estimate of storage marginal costs. The combination of the proposed gas floor, 1.4 price-based opportunity cost multiplier, price adjustment scalar, and time-of-day multiplier will significantly overstate storage marginal costs in nearly all instances, particularly during peak hours when local market power concerns are greatest. Implementing a DEB that systematically overestimates storage costs may allow resources with local market power to submit bids substantially above their marginal cost during hours when mitigation is most important.

DMM recommends that the ISO re-evaluate its proposed storage DEB methodology to avoid substantially increasing storage DEB values without empirical evidence and a clear economic rationale demonstrating that such increases are necessary to accurately estimate storage marginal costs. The ISO should evaluate alternative time-of-day multiplier designs, and should provide empirical analysis of how any proposed designs result in DEB values that are consistent with storage opportunity costs.

DMM supports extending the storage DEB framework to all Western Energy Imbalance Market (WEIM) resources using an approach similar to the negotiated DEB methodology currently used for WEIM storage resources. DMM also supports the ISO’s proposal to implement a price adjustment scalar using a framework similar to the scalar currently applied in negotiated DEB calculations.

DMM views the proposed modifications to the non-generating resource (NGR) bidding model as a potential enhancement for storage resources that could allow them to better represent their costs and operational characteristics to the market. However, the proposed NGR bidding framework would not eliminate the need for storage operators to forecast prices over the day, and the proposed model does not address the inefficient real-time bidding incentives for storage created by the current bid cost recovery (BCR) rules. The proposed NGR bidding model is not a substitute or solution for revised real-time BCR rules for storage resources, and DMM does not believe NGR bidding enhancements should be pursued ahead of, or with higher priority than, redesign of storage bid cost recovery rules. 

DMM supports the “greater of” approach to establish an interim hybrid resource DEB. Implementation of the “greater of” hybrid DEB approach should not be delayed in the event that it becomes overly controversial or time consuming to establish an appropriate minimum technology share value, or there is significant implementation cost or complexity to including the minimum share feature.

Comments

Storage DEB

The time-of-day approach provides a more accurate estimate of storage resource marginal costs than the static approach

The ISO presented two approaches to calculating a storage DEB—the time-of-day approach and the static approach. The time-of-day approach for the discharge DEB introduces four new components: (1) inclusion of a gas floor, (2) a scalar to adjust the prices that determine the price-based opportunity cost, (3) an increase in the price-based opportunity cost multiplier, and (4) a time-of-day multiplier applied in the real-time DEB calculation. While DMM believes the proposed time-of-day approach requires several refinements, it remains preferable to the static approach. Therefore, DMM recommends the ISO continue developing the time-of-day approach to address the concerns discussed in the following sections rather than pursue the static alternative.

The static approach reduces the precision of DEBs by retaining a consistent value throughout the day, and failing to capture changing opportunity costs of storage resources across the day. This approach further reduces precision by relying on electricity pricing hub indices rather than locational marginal prices (LMPs). DMM agrees with the ISO’s assessment that using different proxy prices (default generation aggregation point values for the WEIM-only resources and LMPs for extended day-ahead market resources) appropriately balances consistent treatment across resources with the preservation of more accurate location-specific signals. DMM has also previously noted that during critical system conditions, ICE trading activity can be limited, resulting in index prices that may not accurately reflect underlying marginal costs.[2] Consequently, reliance on hub indices may not accurately estimate the marginal costs of storage resources or adequately mitigate opportunities for market power when those indices are based on limited trading activity. Relying on indices to set DEBs may not accurately estimate marginal costs of storage resources or protect from market power exertion whenever those indices are only set by a low volume of trade.

The design of a DEB should be based on estimating marginal costs, not effectuating a pre-determined bid-stack ordering

Both the static and time-of-day approach incorporate a gas floor into the storage DEB calculation. DMM continues to argue against this component because gas prices are not directly related to the marginal cost of battery resources. To the extent that gas prices affect storage opportunity costs, those effects are reflected through electricity prices and therefore captured in the price-based opportunity cost component.

The ISO acknowledges that the gas floor is not intended to estimate storage marginal costs directly. Instead, the ISO states that the gas floor is included to ensure storage resources are not dispatched ahead of hydro resources when both are mitigated. DMM is not persuaded by this justification. Resource dispatch should result from a cost-minimizing optimization based on the marginal costs, not from an administrative preference regarding the relative ordering of resource types. Storage resources should be dispatched before or after hydro depending on the actual marginal costs of those resources in a given interval.

DMM’s understanding is that the gas floor in the hydro DEB was originally intended to account for replacement energy costs and protect against situations in which real-time prices significantly exceed day-ahead index prices.[3] These concerns are already sufficiently addressed in the storage DEB framework. Unlike the hydro DEBs, the storage DEBs rely on LMPs or default generation aggregation point (DGAP) values that are much more representative of expected real-time prices. Moreover, the ISO proposes additional upward adjustments through the price scalar, the opportunity cost-multiplier, and potentially the time-of-day multiplier depending on the hour. Collectively, these components provide substantial protection against underestimating real-time prices, reducing any justification for adding a separate gas-floor component that could become quite large and determine the DEB in instances when gas prices spike significantly.

More fundamentally, DEB design should not be driven by a desire to place one resource type ahead of another in the bid stack. DEBs are intended to estimate marginal costs, and the methodology for one resource type should not depend on the characteristics of another resource, absent a clear economic rationale. DMM therefore does not see a theoretical basis for incorporating the hydro gas-floor component into the storage DEB.

If an accurate estimate of storage marginal cost results in placement of storage below hydro in the mitigated bid stack, but market participants maintain that hydro dispatch ahead of storage is consistent with relative marginal costs, this is more an indication that the hydro DEB is overstating the marginal cost of hydro resources, rather than justification for inflating a storage DEB informed by marginal cost to ensure storage is dispatched after hydro.

An upward adjustment for the prices used to calculate the price-based opportunity cost appropriately addresses differences in prices across the market runs

The ISO is proposing to incorporate a scaling process for both day-ahead and real-time storage DEBs. The day-ahead storage DEB uses prices from the market power mitigation run to estimate prices in the final day-ahead market run. The real-time storage DEB uses prices from the final day-ahead market run to estimate prices in the real-time market runs. These prices would be scaled up to reflect expected differences between the markets. DMM supports this proposal and recommends the ISO use a similar framework to the one DMM uses to adjust DGAP prices in negotiated DEB calculations for WEIM storage resources.

DMM believes this scalar should remain separate from the time-of-day multiplier. The scalar addresses differences between prices used in the DEB calculation and the prices ultimately realized in the market, whereas the time-of-day multiplier is intended to reflect variation in intraday opportunity costs. These components serve distinct purposes and should remain conceptually separate.

There is no economic basis for applying a 1.4 opportunity-cost multiplier throughout the day

DMM does not support the ISO’s proposal to increase the price-based opportunity cost multiplier from 1.1 to 1.4. The existing price-based opportunity cost framework already estimates the highest opportunity cost of the day by using the Nth-highest hourly price, where N corresponds to the resource’s discharge duration in hours. By construction, this methodology already reflects the highest opportunity cost. The ISO’s proposal using the time-of-day approach would further increase this value through three separate mechanisms: a price-adjustment scalar, the opportunity cost multiplier, and the time-of-day multiplier. DMM cautions that these combined adjustments substantially overstate marginal costs in nearly all instances.

DMM’s analysis indicates that the incremental benefits of higher time-of-day multipliers diminish once the multipliers reach approximately 1.3 or 1.4 in the hours with the highest opportunity cost.[4] Rather than applying those higher values only during hours where opportunity costs are greatest, the ISO proposal effectively applies a 1.4 multiplier across all hours and then includes an additional time-of-day multiplier on top of the 1.4 multiplier. Under this structure, DEBs reach values 1.4 higher than the Nth highest price during the peak hours when storage opportunity costs are lowest, and reach 1.96 times higher than the Nth highest price during the hours prior to the peak.

Given DMM’s finding that that the benefits of higher multipliers diminish beyond 1.4, and the ISO has not provided any additional analysis of potential multiplier values, DMM does not see a basis for effectively applying a multiplier of almost 2x during the hours when opportunity costs are highest. More concerning is the resulting overstatement of storage marginal costs during peak hours when opportunity costs are lowest and local market power concerns are greatest. DMM cautions that the proposed storage DEB calculation may substantially overestimate the marginal costs of storage resources without empirical evidence of additional benefit or economic justification.

Because the proposed price-adjustment scalar already addresses day-ahead versus real-time price differences, and the time-of-day multiplier captures changing intraday opportunity costs, DMM recommends eliminating the separate price-based opportunity cost multiplier altogether. At a maximum, the ISO should retain the current 1.1 multiplier rather than increasing it to 1.4 without a demonstrated theoretical or empirical basis. DMM is not persuaded by the ISO’s justification that 1.4 is the appropriate value because it aligns with the value used in the hydro DEB. 

The time-of-day multiplier should include values below one in order to accurately reflect varying intraday opportunity costs

DMM continues to recommend a time-of-day multiplier that reflects both higher opportunity costs before peak hours and lower opportunity costs during the highest-priced hours. During the highest-priced periods, the opportunity cost for storage resources to discharge declines due to fewer future opportunities for the resource to earn higher revenues. As a result, marginal costs during peak intervals are often lower than those implied by the current DEB framework.

By limiting the multiplier range to 1 or 1.4, the ISO’s proposal addresses concerns regarding premature discharge but does not address the longstanding issue that storage DEBs may significantly overestimate marginal costs during peak hours—the very periods in which local market power concerns are the most significant. DMM’s analysis has consistently shown limited evidence of premature dispatch resulting from storage DEBs that are too low.[5] If the ISO is revising the storage DEB framework to address those infrequent instances, it should also address the more persistent concern that DEBs overstate marginal costs during peak net-load hours. 

DMM agrees that the ISO should be cautious when determining the hours when the multiplier falls below one. However, concerns over determining the appropriate hours for the multiplier to fall below one should not justify a DEB design that does not accurately reflect how storage opportunity costs vary throughout the day. The purpose of the DEB is to mitigate prices that exceed competitive levels due to the potential exercise of local market power. By maintaining a DEB that overestimates storage marginal costs during peak hours, and further increasing those estimates through a higher price-based opportunity cost multiplier, the ISO risks allowing resources with local market power to bid further above their actual marginal costs without being mitigated during the periods when mitigation is most important.

DMM therefore recommends that the ISO incorporate time-of-day multipliers below one in order to better align storage DEBs with the underlying opportunity costs of storage resources and improve the effectiveness of the mitigation framework. DMM recommends that the multiplier should fall below one in a set number of hours over peak demand periods, when the highest prices are likely to occur (e.g., 18-22). Similar to the approach discussed in the section below, this period could be determined by empirical analysis of historical data, and could be configurable to reflect changes over time, e.g., due to seasonality or overall pattern changes.

DMM also recommends the ISO incorporate the time-of-day multiplier into the day-ahead storage DEB as well. It is unclear to DMM why the same multiplier cannot be applied to day-ahead storage DEBs and why the ISO instead proposes to use the upper-bound of the multiplier throughout the entire day. DMM supports aligning the storage DEB structure across the day-ahead and real-time markets to support convergence between the two markets.

The design of time-of-day multipliers warrants empirical analysis

The ISO proposes to transition the time-of-day multiplier from 1.4 to 1 based on the Nth highest-priced hour used to determine the price-based opportunity cost. DMM recommends the ISO conduct empirical analysis to determine the hours in which the time-of-day multiplier would have decreased to lower values under this framework. Such analysis would help assess whether the proposed design accurately captures variation in storage opportunity costs across different market conditions.

DMM remains concerned that the proposed approach may not accurately capture opportunity costs in all circumstances. For example, if the Nth highest price occurs late in the evening, such as hour-ending 22 or later, the higher time-of-day multiplier could apply throughout most of the peak period encompassing the N-1 highest priced hours, even though prices are already elevated and relatively few high-priced intervals remain. In these hours, the opportunity cost of storage resources to discharge may already be declining, making the high multiplier less appropriate. Similarly, there may be periods when day-ahead prices peak higher during the morning ramp than in the evening peak period. In such circumstances, it may not be reasonable to apply the lower time-of-day multiplier throughout the remainder of the day. These examples do not capture every possible outcome, but illustrate the importance of evaluating the proposed methodology using historical data. As discussed below, DMM’s empirical analysis finds that both outcomes occur with meaningful frequency under historical market conditions.

DMM conducted analysis to evaluate the hours in which the ISO’s proposed time-of-day multiplier would decrease. This analysis focuses on the fourth highest-price hour because the vast majority of CAISO storage resources are 4-hour duration. Figure 1 shows the frequency with which each hour of the day was the fourth highest day-ahead LMP based on resource-day level data for all CAISO storage resources during 2024 and 2025. The results indicate that the fourth-highest priced hour occurred most frequently in hour-ending 22, accounting for about 18 percent of observations. Under the CAISO’s proposed methodology, this results in the time-of-day multiplier increasing the DEB during many of the peak hours (18-21), even though true opportunity costs in those hours are much lower. In addition, Figure 1 also highlights that in a significant number of observations, the fourth highest-priced hour occurs earlier in the day. In these instances, the ISO’s proposed methodology could result in the highest DEBs occurring during morning hours and no multiplier during the pre-peak hours when opportunity costs are highest.

Figure 1 – Frequency of hour that time-of-day multiplier would decrease under ISO proposal

 

DMM recommends the ISO consider an alternative mechanism for reducing the time-of-day multiplier during hours with lower opportunity costs. One potential approach would be to use the earliest of the four highest-priced hours, subject to an hourly floor to prevent the multiplier from decreasing too early. Figure 2 illustrates the hour in which the multiplier would decrease under this methodology using the historical data described above. Under this approach, the hour in which the time-of-day multiplier decreases would be the later of (1) earliest hour of the four highest priced hours and (2) hour-ending 18. The floor of hour 18 ensures that the time-of-day multiplier is not lowered inefficiently early based on higher prices in the day. As shown in Figure 2, this alternative time-of-day multiplier would decrease in hour-ending 18 in the majority of observations. However, on days when prices peak later, the reduction may occur in hour-ending 19 or 20. DMM notes that this methodology would more consistently lower the time-of-day multiplier during the hours when storage resource opportunity costs are lowest and conditions may be more susceptible to the exercise of local market power.

Figure 2 – Frequency of hour that time-of-day multiplier would decrease under alternative methodology

 

NGR bidding enhancements

The proposed NGR bidding enhancements could improve storage modeling, but should not be pursued as a higher priority than BCR design for storage resources

The ISO has proposed a bidding enhancement model for storage resources that would replace the current price-quantity pair bidding paradigm with an end-of-horizon opportunity cost framework. The proposed NGR bidding framework would allow storage resources to bid a single-value end-of-horizon state-of-charge (EOH SOC) parameter. This parameter would indicate to the market the shadow value of the stored energy at the end of the horizon, which the current market model does not consider explicitly.

DMM understands that in the day-ahead, the EOH bid would provide a parameter for the market software to optimize storage schedules over the day, given the financial willingness of a resource to deviate between its initial and end-of-day SOC. DMM understands that in real-time, the EOH bid will be an hourly bid to express willingness to deviate from the day-ahead SOC at the end of that hour, which similarly will allow the market to assign a value to the SOC outside of the optimization horizon. The ISO has highlighted that the day-ahead and real-time model will both use the registered variable operations and maintenance (O&M) cost parameter to reflect minimum spreads required to cover variable O&M costs incurred by operating within the optimization horizon.

DMM views the proposed modifications to the NGR bidding model as a potential enhancement for storage resources that could allow them to better represent their costs and operational characteristics to the market.[6] Further, the proposed enhancements would eliminate the need to forecast prices and SOC changes within the optimization horizon. However, as DMM understands the proposed model, resources would still need to forecast prices and expected SOC at points beyond the horizon to inform the value of the EOH SOC bid. In real-time, this amounts to a continued need for an hourly forecast of prices and expected resource positioning over the day in order to establish each hourly EOH SOC value. This is what resources need to do today under the current NGR bidding framework to establish bids that appropriately reflect expected intraday opportunity cost. 

Further, the development and implementation of a new NGR bidding model for storage is a large undertaking that seems likely to require significant resources by the ISO and stakeholders. DMM recommends the ISO continue to prioritize BCR design for storage resources and ensure that work on other storage market design changes does not further delay work on storage BCR design. DMM notes that because the proposed NGR bidding enhancements do not address the real-time BCR issues, and because real-time BCR rules must still be developed to handle instances of day-ahead schedule buybacks due to insufficient SOC, BCR rules can and should be developed independently and ahead of any enhancements to the NGR bidding model.

The NGR bidding concept does not address issues with the BCR design for storage resources

The ISO indicated in the straw proposal that this proposed improvement addresses, “[a] key issue[…] regarding storage bid cost recovery: unlike other resources, batteries are not exposed to real-time prices when they fail to meet their day-ahead schedules.” However, the proposal as described does little to nothing to address real-time BCR received when the real-time SOC is not sufficient to meet a day-ahead schedule. Differences between day-ahead and real-time SOC will still occur as they do today. 

Using the day-ahead SOC at the end of each optimization horizon as a reference point for the EOH SOC bid does not impact a resource’s willingness to deviate from that value in real-time. Like real-time energy bids today, the value reflected in the EOH SOC bid would still be determined by expected real-time prices over the day, and estimated intraday opportunity costs based on exposure to those real-time prices when deviation occurs. The proposal does nothing to modify existing BCR rules that insulate storage resources from exposure to real-time prices when day-ahead schedules are undeliverable due to insufficient SOC. Therefore, the proposed approach does not solve DMM’s core concern that the current BCR design does not incentivize efficient real-time bidding by storage resources.[7]

If pursued, the proposed NGR bidding concept should allow storage resources to represent opportunity costs across the full range of SOC

The ISO is proposing to implement a biddable price parameter to allow scheduling coordinators to represent the value of stored energy beyond the market model horizon. However, the ISO has proposed the bidding improvement with just one end-of-horizon opportunity cost. The opportunity value of the stored energy is dependent on the SOC of the resource, and the current formulation of the EOH SOC bidding proposal only takes a single value of the EOH SOC. This assumes the SOC range has an opportunity cost that scales linearly across the full range of SOC.

Deviating from the reference SOC value by different amounts can carry different costs for the resource in future intervals. The opportunity value of the stored energy does not scale linearly, and allowing scheduling coordinators to reflect the opportunity of the stored energy across the SOC range may require the scheduling coordinator to have the ability to submit multiple bid pairs associated with different values of SOC. DMM recommends the ISO evaluate whether multiple SOC-price pairs, or another piecewise representation of terminal opportunity value, would better reflect the economics of stored energy than a single EOH-SOC value.

DMM recommends the ISO detail the tradeoffs between the risk and reward using the proposed bidding concept

The current framework for storage resources allows the scheduling coordinators to reflect private estimates of their costs and benefits in their bidding strategies across the optimization horizon. The new bidding concept reorients a larger portion of the financial decisions of the resource into the market optimization, whereby the day-ahead schedule uses the bid spreads to generate a profit maximizing schedule. The real-time schedule would then attempt to follow the profit maximized day-ahead schedule unless the bid value of stored SOC at the end of each optimization horizon results in deviations from the day-ahead SOC trajectory.

The proposed EOH SOC bidding framework reduces the number of bidding dimensions available to storage resources. In day-ahead, this reduces the need for resources to reflect forecasts of hourly prices through hourly bid adjustments. In real-time, the proposal reduces the need to forecast prices and resource movement between the time of bid submission and the end of the operating hour. The proposal would also place greater reliance on the ISO market model to determine economically efficient charging and discharging decisions within the optimization timeline.

DMM recommends the ISO provide additional analysis describing how the proposed framework changes the allocation of risk and reward between market participants and the market optimization, including the implications for storage revenues, dispatch efficiency, and future bid cost recovery design.

DMM continues to emphasize the need for clarity and consideration of market power mitigation impacts with the new bidding concept

DMM requests the ISO more generally elaborate on the intended direction with SOC bidding, if this framework is likely to be further developed and pursued in the near future. As SOC bidding functionality is explored, it will be important to consider how market power mitigation may work in SOC-based bidding frameworks. Unlike cost-based bids for a given energy output level, the reference levels of SOC bids are not as readily observable and have the possibility of leading to new gaming strategies or exercise of market power. As a result, SOC bidding frameworks will need to be jointly evaluated with future DEB enhancements.

Hybrid resource DEB

DMM supports the “greater of” approach to establish an interim hybrid resource DEB

Hybrid resources currently do not have a DEB, and are not subject to local market power mitigation. DMM continues to place a high priority on the development of a hybrid resource DEB to facilitate local market power mitigation for hybrid resources. DMM previously supported development of a hybrid resource DEB in the near-term by calculating the maximum of the DEBs that apply to each of the generation components that make up the hybrid resource. This aligns with the “greater of” approach the ISO has outlined in the straw proposal. This initial approach should be easy to implement and should achieve the goal of subjecting hybrid resources to local market power mitigation.

As part of the “greater of” approach, the ISO proposes to establish a minimum share requirement, where a given technology would have to account for a minimum share of the overall hybrid capacity for that technology’s DEB to be considered in the “greater of” calculation. DMM sees the concern addressed by this proposal, and agrees that this would be an effective approach to prevent the hybrid DEB from significantly exceeding the marginal cost of the large majority of the hybrid generation capacity in a resource. However, DMM notes that given the composition of the existing hybrid resource fleet, and the intended interim nature of this approach for hybrid resource DEBs, implementation of the “greater of” hybrid DEB approach should not be delayed in the event that establishing an appropriate minimum share value becomes overly controversial or time consuming, or there is significant implementation cost or complexity.

After a near-term solution for hybrid resource DEBs is developed, the ISO should prioritize additional hybrid resource DEB enhancements to more accurately reflect the costs of hybrid resources as a full system of different generation components.

 

 


[1]  Storage Design and Modeling: Straw Proposal on Default Energy Bids, Uplift, and State-of-Charge Management, California ISO, July 15, 2026: https://stakeholdercenter.caiso.com/InitiativeDocuments/Straw-Proposal-Storage-Design-and-Modeling-Uplift-DEB-Outage-Management-State-of-Charge-Jul-15-2026.pdf

[2]  Comments on FERC Order 831 – Import Bidding and Market Parameters Final Proposal, Department of Market Monitoring, September 10, 2020: https://www.caiso.com/documents/dmmcommentsonfercorder831-importbiddingandmarketparametersfinalproposal-sep102020.pdf

[3]  CAISO Tariff Amendments to Enhance Local Market Power Mitigation and Reflect Hydroelectric Resource Opportunity Costs in Default Energy Bids. California ISO, July 2, 2019: http://www.caiso.com/Documents/Jul2-2019-TariffAmendment-LocalMarketPowerMitigationEnhancements2018-ER19-2347.pdf

[4]  Comments on Storage Design and Modeling Working Group Presentation on March 16, 2026, Department of Market Monitoring, April 3, 2026: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-mar-16-2026-working-group-presentation-apr-03-2026.pdf

[5]  2024 Special Report on Battery Storage, Department of Market Monitoring, May 29, 2025: https://www.caiso.com/documents/2024-special-report-on-battery-storage-may-29-2025.pdf

[6]  Comments on Storage Design and Modeling Working Group Presentation on January 22, 2026, Department of Market Monitoring, February 17, 2026: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-jan-22-2026-working-group-presentation-feb-17-2026.pdf

[7]  Ibid.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

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 comments on the straw proposal for storage default energy bid enhancements.

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 comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

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 comments on the straw proposal regarding hybrid default energy bids.

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 comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

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 comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

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 any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

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.

California Public Utilities Commission - Public Advocates Office
Submitted 08/05/2026, 04:55 pm

Contact

Paul Worhach (paul.worhach@cpuc.ca.gov)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

The Public Advocates Office at the California Public Utilities Commission (Cal Advocates) appreciates the opportunity to comment on the California Independent System Operator Corporation’s (CAISO) July 22, 2026 meeting on CAISO’s Storage Design and Modeling Initiative (Workshop)[1] and the July 15, 2026 Straw Proposal on Default Energy Bids, Uplift, and State-of-Charge Management Topic Groups (Straw Proposal).[2]

Cal Advocates provides the following comments on the Workshop and the Straw Proposal:

  • CAISO’s proposed real-time (RT) storge default energy bid (DEB) methodology may significantly overestimate RT opportunity costs and result in unduly high DEB values and distorted market prices.
  • CAISO should use RT time-of-day (TOD) shaping factors with a minimum value of 1.0 before morning and evening peak periods and a value of less than 1.0 during morning peak hours and during and after evening peak periods.
  • CAISO should conduct an updated empirical study jointly for storage and hydro to set the opportunity cost multiplier, day-ahead (DA) and RT price scalars, and TOD shaping factors to establish a consistent DEB methodology for storage and hydro.
  • CAISO should adopt the “greater-than” approach for hybrid DEBs based on an interim minimum 50% capacity-based share for the hybrid resource with the greater DEB.  Longer-term, CAISO should conduct an empirical analysis to set either a capacity-based or an energy-based minimum requirement to ensure that most hybrid resources can operate in a manner consistent with stand-alone and co-located storage without unnecessarily inflating the hybrid DEB.

 


[1] CAISO, Storage Design and Modeling Working Group on Uplift & Default Energy Bids and Outage Management, July 22, 2026 (Workshop Slides).  Available as “Presentation - Storage Design and Modeling – Jul 18, 2026” at: https://stakeholdercenter.caiso.com/StakeholderInitiatives/Storage-design-modeling.

[2] CAISO, Storage Design and Modeling Second Revised Straw Proposal on Outage Management Topic Group, July 15, 2026.  Available as “Straw Proposal - Storage Design and Modeling - Uplift, Default Energy Bids, and State-of-Charge Management - Jul 15, 2026” at: https://stakeholdercenter.caiso.com/StakeholderInitiatives/Storage-design-modeling.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

CAISO’s near-term timeline to complete a draft final proposal by the end of 2026 is reasonable, given the significant effort expended in the Storage Modeling and Design initiative to date.  However, it is not clear whether CAISO intends to include bid-cost recovery (BCR) within the scope of the draft final proposal.  CAISO states that near-term efforts will focus on DEBs and “introducing new bidding concepts,” while longer term efforts will consider BCR reform.[1]  CAISO should focus near-term efforts on DEB and BCR reform, while continuing to develop more fundamental market design changes at a steady pace outside the scope of the immediate proposals.

The development of a new market design and bidding structure for storage resources is a multi-year effort that will involve considerable and focused CAISO and stakeholder participation.  A near-term timeframe is insufficient to introduce new concepts and develop a draft final proposal in a robust manner and would misallocate resources away from the more immediate need for DEB and BCR reform.  CAISO should adopt CAISO’s Department of Market Monitoring’s recommendation to continue to prioritize BCR reform ahead of other storage market design changes.[2]  CAISO should include BCR reform within the scope of the final draft proposal.

 


[1] Straw Proposal at 4.

[2] Department of Market Monitoring, Comments on May 18, Session 14 on Second Revised Straw Proposal on Uplift and Default Energy Bids (DEB), Outage Management, June 5, 2026.  Available at: https://stakeholdercenter.caiso.com/Comments/AllComments/df58b4fb-60d0-4455-a93d-76cf99d51c22#org-f8093cd6-086b-4e19-ac64-163c522f3044.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

CAISO proposes to adopt a DA and RT storage DEB methodology based upon the existing DEB methodology for hydro resources[1] that CAISO developed and adopted in 2018 and 2019 for DA and RT.[2]  CAISO proposes to align the parameters in the storage DEB with the hydro DEB to maintain consistency so that the relative bid-stack positions of hydro and storage are maintained under mitigation.[3]  

CAISO would set the DA DEB to the maximum of: (1) the storage variable operation cost times 1.1, (2) a price-based opportunity cost proxy multiplied by a scalar to account for recent price divergence between the DA market and the market power mitigation (MPM) run,[4] times 1.4, and (3) a “gas floor” component times 1.1 to represent the marginal cost of a gas plant with a heat rate of 11.088 million British Thermal Units (MMBtu) per mega-watt-hour (MWh).[5]  

CAISO would set the storage RT DEB in a similar manner, but with a multiplier in component (2) to account for recent price divergence between the RT and DA markets.[6]  In addition, CAISO would multiply the final RT DEB by an hourly TOD shaping factor of 1.0 for all hours after the hour that sets the proxy opportunity cost, and 1.4 for all hours before the proxy opportunity cost hour.[7]  CAISO would use the TOD shaping factor to represent time-varying RT opportunity costs.[8]  Cal Advocates anticipates that, in most cases, the opportunity cost portion of the formula will determine the DEB, particularly during tight conditions when it is most important to have accurate DEBs for market power mitigation.

The purpose of the price scaling in component (2) is to capture divergences between market pricing runs over the three days prior to the operating day.  CAISO describes this scaling as a way of addressing “stale” values in the DA and RT opportunity costs.  This scaling could introduce more accurate prices if, for instance, the prices in the MPM run were consistently lower than the DA settlement prices.  However, CAISO proposes that the floor of the scaling ratio be set to 1.0, so that prices are always scaled upwards, and not downwards, even if the MPM or DA prices are higher than the DA or RT prices, respectively.[9]   As such, price divergence that reflects lower opportunity costs in the DA and RT markets would be ignored.  This means that the DEB will be scaled up, providing storage resources with greater opportunity to exercise market power, but never down.  Moreover, if CAISO were to adopt the price divergence scaling in component (2), there are temporal complications that CAISO should take into consideration.  The proposed use of a three-day historical proxy will mean that weekday scaling will include price patterns on weekends, and vice versa.  Weekday and weekend days have consistently different pricing patterns, so the scaling may introduce more errors than it resolves.

There are two significant differences between CAISO’s latest Straw Proposal and a similar earlier proposal.[10]  First, CAISO previously proposed that the hourly TOD shaping factors take on values below 1.0, as well as above 1.0, to properly represent dynamic RT opportunity costs that vary below and above the static DA proxy opportunity cost.  CAISO’s prior proposal would set the shaping factors to values between 0.6 and 1.4 throughout the day to represent hours with higher opportunity costs, including hours leading up to the morning and evening peak hours, and lower opportunity costs, such as hours during the morning and evening peaks.[11]  Cal Advocates supported CAISO’s earlier proposal because a TOD factor that varies below and above 1.0 mitigates both the underestimation and overestimation of the RT opportunity cost.[12]  Second, CAISO previously proposed that the RT DEB exclude the 1.1 factor for the variable operation cost and the gas floor and the 1.4 factor for the opportunity cost proxy.  CAISO instead represented time-varying opportunity costs with the TOD shaping factor.  CAISO’s latest Straw Proposal would have CAISO include both the opportunity cost multiplier and the revised TOD shaping factor,[13] which would effectively double pad the DEB calculation and produce a far higher DEB than may be necessary or warranted.

There are five issues of concern in CAISO’s proposed storage DEB methodology: (1) the use of a 1.0 floor for TOD shaping factors, (2) the use of a 1.4 TOD shaping factor in the hours before the hour that sets the proxy opportunity cost and a 1.0 factor in the hours after the hour that sets the proxy cost, (3) the use of three-day historical prices to scale proxy opportunity costs up and not down, and the use of non-representative days to scale weekday and weekend prices, (4) the use of the 1.4 opportunity cost multiplier in the RT DEB calculation together with minimum 1.0 TOD shaping factors, and (5) the use of the 1.4 multiplier from the potentially outdated 2018 hydro DEB formula for current and future storage resources.  Cal Advocates addresses these concerns in the following sections.

 

CAISO should use TOD shaping factors with a minimum value of 1.0 before morning and evening peak periods and a value of less than 1.0 during morning peak hours and during and after evening peak periods.

CAISO’s problem statement for DEB reform indicates that TOD DEBs are necessary to properly value storage’s time-varying RT opportunity costs to avoid overestimating and underestimating the opportunity costs in the DEB calculation.[14]  Storage opportunity costs are highest in the hours preceding system peaks because there is greater economic value in accumulating and holding a state-of-charge during lower priced periods and dispatching later at higher system prices.  Storage opportunity costs are lowest during and after system peaks, because there is minimal or no value in holding state-of-charge during the highest priced hours to dispatch later at lower prices.  CAISO’s proposal fails to address the overestimation of opportunity costs and fails to address the risk of setting the DEB at too high a value during and after system peaks.

If a storage resource is mitigated in the Local Market Power Mitigation (LMPM) process to a DEB value that is too low, CAISO may dispatch the resource prematurely in the RT market and deplete the storage’s state-of-charge.[15]  Consequently, the resource may not be available when CAISO needs it during peak periods, and the resource would miss out on a higher arbitrage value between earlier non-peak and later peak period prices.  Conversely, if the resource is mitigated to a too-high DEB, CAISO may instead dispatch other resources, such as emitting gas resources, precisely when storage is most needed to meet the system peak.  If CAISO dispatches a market power seeking storage resource after mitigation, the resource could set the market clearing price at an unduly high mitigated DEB and thereby increase system costs for ratepayers.

CAISO should find a balance between a DEB that is high enough to avoid premature dispatch under mitigation and a DEB that is too high to dispatch storage or otherwise reward market power seeking resources at an unduly high DEB.

It is reasonable to set the minimum TOD shaping factor value to 1.0 in hours preceding peak hours when there is greater value for storage to accumulate and hold state-of-charge, so that the RT opportunity cost is not set below the DA proxy opportunity cost.  CAISO should conduct a study to determine the appropriate hourly shaping factor above 1.0 for hours preceding morning and evening peaks based on empirical market data.  CAISO should set the TOD shaping value to a level that ensures that mitigated storage is not prematurely dispatched, within a reasonable tolerance level, such as 95 percent.[16]  Similarly, CAISO should set the TOD shaping factor during and after peak periods to a value of less than 1.0, within a similar tolerance level, to ensure that mitigated storage is dispatched when needed during peak hours, and that mitigated storage does not unduly distort peak market clearing prices when dispatched.

 

CAISO’s proposed RT storge DEB may significantly overestimate RT opportunity costs and result in unduly high DEB values and distorted market prices.

CAISO proposes using several factors, all greater than or equal to 1.0, that are multiplied together within the DEB calculation.  Cumulatively, the product of these values creates a value that may significantly overestimate hourly RT DEBs.  CAISO proposes to use (1) a 1.4 factor for the opportunity cost proxy in the RT DEB formula, (2) a TOD shaping factor that takes values of 1.0 or 1.4, and (3) hourly RT price multipliers that increase but do not decrease the proxy opportunity cost component.[17]  If the opportunity cost proxy times 1.4 sets the RT DEB in hours preceding the peak period, the resulting hourly DEBs would be a minimum of nearly two times the DA opportunity cost proxy and would be even higher if the RT scaling factors exceed the minimum value of 1.0.

Likewise, peak period DEBs, if set by the DA opportunity cost proxy, would be a minimum of 1.4 times the DA proxy, and even higher if the RT scaling factors exceed 1.0.  If CAISO applies a minimum factor of 1.4 to already overestimated opportunity costs, it risks distorting real-time peak period energy clearing prices, resulting in increased costs to ratepayers and reduced market efficiency.

CAISO should instead conduct a comprehensive study that includes both hydro and storage resources to appropriately set the DA and RT DEB parameters, as discussed further below.

CAISO should conduct an empirical study to set the opportunity cost multiplier in the DA and RT DEB formulas jointly for hydro and storage resources.

CAISO developed the hydro DEB methodology in 2018 to capture opportunity costs for hydro resources to sell energy in markets outside of the CAISO balancing area.[18]  As such, the empirical study that CAISO used to set the DEB formula parameters was limited to consideration of four hydro trading price hubs using data from October 2017 to September 2018.[19]  CAISO assumed that hydro resources have up to 3 months of available storage,[20] and CAISO acknowledged that hydro opportunity costs are complex and are impacted by uncertain conditions including water inflow, downstream conditions, and legal water management considerations, leading to opportunity costs that may change “drastically” within the same operating day.[21]  CAISO’s analysis concluded that a 1.4 multiplier for the opportunity cost component was necessary to ensure that hydro resources with up to 3 months of storage capacity are not dispatched more than 4 hours per day in a conservative range of 95-99% of the time across the four studied trading hubs.[22]  CAISO has not updated the hydro DEB calculation’s 1.4 multiplier since it was adopted in 2019.[23]

It is not appropriate to assume that the 1.4 multiplier CAISO developed for the hydro DEB is at all appropriate for energy storage resources located within the CAISO balancing area.  There were very few storage resources in the CAISO balancing area between 2017 and 2018, compared with nearly 17 gigawatts (GW) of storage in 2026.[24]  Battery energy storage lacks most of the complex constraints that affect hydro opportunity costs.  Moreover, the metric CAISO used in its hydro DEB study – less than four hours of dispatch per day – fails to capture when the four hours of dispatch occur.  The timing of dispatch and the selected tolerance level are critical to the question of the appropriate multiplier.   By not accounting for timing and tolerance, CAISO may set storage DEBs to unnecessarily high values, which may distort market clearing prices and burden ratepayers with undue market costs.

There may be value in aligning energy limited hydro and energy limited storage DEBs to ensure consistent storage and hydro bid stack positions under mitigation.  However, CAISO should not apply an inappropriately high multiplier derived from an empirical study of exporting hydro resources in 2017 and 2018 to the current 17 GW of energy storage that operates within the CAISO balancing area. Nor should CAISO apply that same inappropriately high multiplier to the projected 13 GW that will come online by 2029.[25]  Rather, CAISO should conduct an updated empirical analysis to determine an appropriate opportunity cost multiplier for storage as the predominant system resource.  CAISO should then reassess the impact on hydro resources and apply an appropriate factor that is consistent to maintain the relative resource bid stack positions under mitigation.  CAISO should, in tandem, conduct an empirical analysis to select the appropriate hourly TOD shaping factors that, when used together with the opportunity cost multipliers, result in DEBs that achieve the dual objective of mitigating both the overestimation and underestimation of time-varying RT opportunity costs.

 


[1] Straw Proposal at 24.

[2] CAISO, Local Market Power Mitigation Enhancements Initiative, Final Draft Proposal (Updated), January 31, 2019 (LMPM Enhancements Final Updated Draft) at 32-42.  Available as: “Draft Final Proposal - Local Market Power Mitigation Enhancements (updated Jan 31, 2019)” at https://stakeholdercenter.caiso.com/StakeholderInitiatives/Local-market-power-mitigation-enhancements-2018.

[3] Straw Proposal at 15.

[4] The final DA proxy opportunity cost in the maximum function is set to the nth highest hourly price of the scaled DA prices, where n is the duration of the storage resource.  The scaled DA prices are calculated by multiplying the prompt DA prices by the ratio of the prior three-day average of DA prices to the price outputs from the MPM.  The same method is used to determine the RT proxy opportunity cost.

[5] Straw Proposal at 22-23.

[6] Straw Proposal at 23.

[7] The nth highest priced hour is the hour that sets the proxy opportunity cost.  See footnote 8.

[8] Straw Proposal at 15.

[9] Straw Proposal at 23.

[10] CAISO, Storage Design and Modeling Working Group on Uplift & Default Energy Bids, and Outage Management, May 18, 2026 at 23.  Available as: “Second Straw Proposal on Outage Management Topic Group - Storage Design and Modeling - May 07, 2026” at https://stakeholdercenter.caiso.com/StakeholderInitiatives/Storage-design-modeling.

[11] Straw Proposal at 15.

[12] Cal Advocates, Comments on May 18, session 14 on Second Revised Straw Proposal on Uplift and Default Energy Bids (DEB), Outage Management, June 5, 2026, Response to Question 2.  Available at: https://stakeholdercenter.caiso.com/Comments/AllComments/df58b4fb-60d0-4455-a93d-76cf99d51c22#org-43bd9820-8430-47c0-a347-9c7954478149.

[13] Straw Proposal at 23.

[14] Workshop Slides at 17.

[15] Premature CAISO dispatch is in part a consequence of the RT market’s limited 75-minute lookahead period, which fails to capture storage’s full charge-discharge storage cycle over multiple hours.

[16] CAISO used a similar tolerance range in setting the hydro DEB parameters.  See LMPM Enhancements Final Updated Draft at 40.

[17] Straw Proposal at 23.

[18] LMPM Enhancements Final Updated Draft at 32.

[19] LMPM Enhancements Final Updated Draft at 38.

[20] LMPM Enhancements Final Updated Draft at 39.

[21] LMPM Enhancements Final Updated Draft at 33.

[22] LMPM Enhancements Final Updated Draft at 33.

[23] See CAISO Fifth Replacement Tariff, May 1, 2026 at Section 39.7.1.7.1.2.  Available as “Section 39 - Market Power Mitigation Procedures as of May 1, 2026” at https://www.caiso.com/legal-regulatory/tariff.

[24] California Public Utilities Commission, Resource Tracking Data, June 2026 (Resource Tracking Report) at 11.  Available as “June 2026 Resource Tracking Data, 7/23/2026” at https://www.cpuc.ca.gov/industries-and-topics/electrical-energy/summer-2021-reliability/tracking-energy-development/cpuc-resource-tracking-data-reports.

[25] Resource Tracking Report at 11.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

CAISO should adopt a TOD approach,[1] conditional on significant modifications as described in response to Question 3.  The static approach would continue to potentially overvalue and undervalue RT opportunity costs.  A TOD approach, if modified to include TOD scaling factors below and above 1.0 and appropriate opportunity cost scalers, would appropriately capture time-varying RT opportunity costs that are higher than a static DA proxy leading up to peak periods, and lower during and after peak periods.  If CAISO does not make these modifications, then it should not adopt either the proposed TOD or static approach.

 


[1] Straw Proposal at 34.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

CAISO’s proposal to apply a “greater-of” approach under which a hybrid resource’s DEB would be equal to the greater of the DEB values applicable to each of the components that make up that hybrid resource, with a minimum share requirement for the resource with the larger DEB, is generally reasonable.[1]  CAISO should set the DEB at a value that is sufficient to ensure that the resource operator is able to manage the state-of-charge of the underlying storage asset in a similar manner as stand-alone resources.  CAISO should ensure that the component that is used to set the DEB makes up a significant portion, if not the majority, of a hybrid resource’s generation output to the CAISO grid.  However, it is not clear that a capacity-based minimum share is sufficient to represent the temporal energy-based output of each of the resources in a hybrid configuration.  For example, one of the hybrid components may primarily generate during hours before the peak, and a different component may output during peak hours.  Adding to the challenge, CAISO does not have visibility into individual resource output but only sees aggregate output.  However, in the interest of moving the adoption of a hybrid storage DEB forward, Cal Advocates supports a minimum 50% capacity-based share requirement for the component that sets the hybrid DEB, or a majority share if the hybrid is composed of three or more resources. 

Hybrid resources are currently not subject to mitigation.  CAISO should not perpetuate the status quo by further postponing development of a hybrid DEB policy, which treats hybrids more favorably than standalone or co-located storage resources.  Without a CAISO-applied DEB, hybrid resources will continue to be exempt from market power mitigation, which enables hybrids to exert market power in ways that could harm both consumers and market efficiency. 

 


[1] Workshop Slides at 34.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

CAISO should conduct a study of hybrid resource market operations to set the minimum component requirement, in line with Cal Advocates’ recommendation that CAISO conduct a study for the RT and DA storage DEB, for use in a longer-term modification of hybrid DEBs.  CAISO’s study should ensure that hybrid resources with a given minimum component percentage are able to manage hybrid storage state-of-charge in an equivalent manner to standalone and co-located storage, without unnecessarily inflating the DEB over a wider range of underlying resource compositions.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

In light of energy storage’s growing dominance on the CAISO grid, Cal Advocates acknowledges and supports the need for a fundamental longer-term storage market and bidding re-design.  A holistic re-design of storage market structure could address many of the issues that are under consideration in this initiative.  However, fundamental reform will require a long-term effort with significant CAISO and stakeholder participation, as well as significant long-term effort in implementing, monitoring, and validating market operations.  In addition, market participants will need to invest considerable effort and time to adapt to a new market.  It is unlikely that new market systems and rules will be fully in place in the near future.  Consequently, until CAISO can fully implement a new storage market design, CAISO’s near and mid-term efforts should focus on reforming the existing BCR and DEB rules such that the market operates in the most efficient manner and provides the greatest benefits for ratepayers.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

Cal Advocates does not have additional comments at this time.

NextEra Energy
Submitted 08/05/2026, 01:53 pm

Contact

Jennifer Solomon (jennifer.solomon@nexteraenergy.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

NextEra Energy Resources, LLC, (“NextEra Energy Resources”) appreciates the opportunity to comment on the CAISO Straw Proposal for Uplift, Default Energy Outage Management, and State of Charge (“Straw Proposal”). NextEra Energy Resources’ comments focus on the proposed concept for reframing non-generator resource (NGR) bidding for storage resources. While NextEra Energy Resources recognizes CAISO's goal of improving state-of-charge (SOC) management and dispatch efficiency, NextEra Energy Resources is not supportive of the reframing concept at this stage. As discussed in further detail below, the proposal raises fundamental design questions that must be resolved before this concept can be meaningfully evaluated. At this time, NextEra Energy Resources recommends CAISO to focus on other scoped topics, including default energy bids (DEBs) and uplift. To the extent CAISO continues to focus on pursuing participation model bid design changes, NextEra Energy Resources recommends that it not be considered as a replacement for the current NGR bidding design, but another option that storage could voluntarily choose while still having access to the current storage bid model.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

 NextEra Energy Resources has no comments at this time.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

 NextEra Energy Resources has no comments at this time.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

 NextEra Energy Resources has no comments at this time.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

 NextEra Energy Resources has no comments at this time.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

 NextEra Energy Resources has no comments at this time.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

 CAISO’s proposed reframing of storage bidding would replace interval-by-interval charge and discharge bids with a single bid or offer to deviate end-of-horizon state-of-charge from a reference value.[1] NextEra Energy Resources is concerned that this effectively transfers operational control over dispatch timing and cycling to the CAISO market optimization. Under the current framework, storage operators retain meaningful ability to influence and manage when assets charge and discharge through interval-level bid curves, enabling management of cycle count and equipment constraints. Replacing this granular control with a single terminal value bid removes that operational influence and delegates dispatch sequencing entirely to the market optimization, which NextEra does not support given the unresolved concern and market design questions described below.

 

CAISO states that the reframed approach lessens the need for interval-by-interval price forecasting.[2] However, submitting a meaningful bid reflecting the "expected value of energy after the market horizon" still requires the operator to assess forward energy values beyond the optimization horizon. It may be difficult for market participants to conduct centralized price forecasting in confidence. In addition, as discussed in detail below, NextEra Energy Resources believes the conceptual proposal creates several critical design questions.

 

Concerns Regarding Strategic Bidding

NextEra Energy Resources is concerned that replacing today's segmented energy bid curves with a single terminal state-of-charge (SOC) scalar may significantly reduce the ability of storage resources to express legitimate economic preferences and operational strategies. A single scalar cannot convey the same breadth of information currently reflected in a ten-segment energy bid curve, including asymmetric willingness to charge versus discharge within the same optimization horizon, varying opportunity costs across hours, alignment with financial transmission rights (FTRs), resource adequacy (RA) obligations, or hedge positions, and prioritization of ancillary service awards when ancillary service value exceeds expected energy arbitrage revenues. CAISO should explain how these legitimate economic preferences would continue to be represented under the proposed participation model and through what specific optimization mechanisms they would be preserved.

 

Under today's segmented bidding, resource-specific cycling cost and opportunity costs are appropriately managed by the market participant through their energy bid curves shape. This flexibility allows participants to optimize dispatch across the entire operating horizon based on their own commercial expectations and operational objectives. For example, a storage resource may rationally choose to discharge at prices that appear below an assumed marginal cycling cost in order to create SOC headroom for an anticipated low-priced charging opportunity later in the day. Likewise, a participant may intentionally charge during a period with limited immediate economic value to position the resource for a higher-value discharge opportunity in subsequent hours. These are economically efficient participant optimization decisions, not market inefficiencies, and they rely on the market participant's ability to determine when and how opportunity costs are reflected in its bids. CAISO should explain how comparable flexibility will be preserved when the market participant's intent is represented solely through a terminal SOC scalar.

 

The proposed framework also raises important implementation questions that require further clarification before stakeholders can fully evaluate the design. Specifically, CAISO should:

  • Specify the units, sign convention, allowable range, and tariff treatment of the terminal SOC scalar;
  • Clarify whether a single value applies symmetrically to both charging and discharging deviations;
  • Explain how DEB mitigation would apply when a resource no longer submits a per-megawatt-hour energy bid curve. In particular, CAISO should clarify whether the terminal SOC scalar itself would be subject to mitigation or caps, and the economic rationale supporting that approach and;
  • Confirm whether real-time bidding would remain anchored to the day-ahead cleared SOC trajectory and whether participants would still be required to calibrate the terminal SOC scalar based on expected future market prices. If so, CAISO should explain how this represents a simplification for market participants and that forecasting burden is actually reduced.

 

Impact on price formation

NextEra Energy Resource is unclear how locational marginal prices (LMPs) would form when the marginal bidder at a given interval no longer submits a per-megawatt-hour energy price but only a scalar willingness to end the horizon with a different state of charge. CAISO should explain how the proposed framework preserves efficient price formation and whether the loss of bid-curve granularity could diminish informational value for market prices. Today, storage bid curves provide information regarding incremental opportunity costs of charging and discharging across different operating ranges, allowing market prices to reflect the marginal value of energy at various output levels.

 

CAISO should also evaluate whether replacing the ten-segment bid curve with the singular scalar parameter could reduce price discovery, especially during intervals where storage is the marginal unit that sets the clearing price. A scalar representation conveys substantially less information than a segmented energy bid curve and may therefore weaken the relationship between resource costs and market outcomes. This has broader implications not only for dispatch efficiency, but also for scheduling coordinators, hedge counterparties, and forward-market participants that rely on transparent and economically meaningful price signals for contracting, risk management, and investment decisions.

 

Interactions with Resource Adequacy

CAISO has not addressed how the reframed bidding paradigm interacts with resource adequacy must-offer obligations. It is unclear how a single end-of-horizon state-of-charge bid satisfies must-offer obligation compliance requirements or how compliance would be assessed. NextEra Energy Resources requests that CAISO clarify how RA availability is demonstrated under this construct and how RAAIM penalty exposure would be assessed when the operator does not control interval-level dispatch decisions.

 

Daily Cycle Count and Grid Charging Constraints

Battery storage resources often have cycle count limits that affect degradation and long-term asset life. It is unclear whether the market participant would retain the ability to specify a maximum daily cycle count constraint in the day-ahead market via the Maximum Daily Energy Limit, Maximum Daily Generating Energy Limit, and/or Maximum Daily Load Energy Limit parameters, or how the optimization would otherwise respect equipment-based limits not captured in a single terminal value bid. Similarly, some storage operators may choose to manage daily cycling limitations by structuring their hourly offer curves to include significant spreads between the charging and discharging portions. Without such mechanisms, the proposed framework could expose resources to excessive cycling and uneconomic degradation.

 

CAISO should also provide details on how the grid charging constraints would function. Specifically, NextEra Energy Resources requests CAISO to confirm that storage operators would continue to be able to submit hourly Off-Grid Charge Indicator (OGCI) bid parameters to indicate their willingness to charge from the grid, even if they would no longer submit hourly energy offer curves under the proposal.

 

Interactions with Ancillary Services Awards

CAISO should also explain how ancillary service bidding and awards would interact with the single end of horizon bid. Specifically, CAISO should clarify whether storage operators would continue to submit ancillary service offers, and if so, how those would be co-optimized against energy given that storage operators would no longer be submitting hourly energy offer curves under the proposal. In addition, CAISO should clarify whether the Ancillary Service State of Charge constraint, attenuation factors for Regulation, and other related deliverability constraints would continue to be enforced to ensure the feasibility of ancillary service awards. It is unclear whether the optimization will continue to reserve the state-of-charge needed to fulfill such awards and whether market participants would be penalized or compensated if the resource cannot achieve its target end of horizon SOC due to its ancillary service commitments. Without clarity on these questions, the proposal creates significant operational and financial risk for resources that wish to participate in the ancillary service market.

 

It is also unclear how the resource will bid into the ancillary service market for each eligible product using the SOC bid. CAISO should explain how the proposed framework will allow NGRs the same access to ancillary services and provide examples of how it would work in practice.

 

Operational Impacts

 

Based on the explanation, it appears that when market conditions don’t justify changing the resource’s end of horizon SOC relative to its beginning of horizon SOC, the storage resource will effectively be optimized based on the variable operations cost (VOC) component, round trip efficiency, and the cost of charging energy within the optimization. This essentially makes the VOC cost the hurdle rate for energy arbitrage throughout the day.

 

This approach won’t fully capture the intertemporal opportunity cost of stored energy. This may result in the optimization discharging the battery too early since the optimization doesn’t adequately value the option of holding energy for future higher price periods. This design could lead to reduced market revenues for storage while also leading to potentially higher relative peak prices under certain conditions. CAISO should provide more details on how the price and non-price portions of storage bids will interact differently under this proposal and investigate possible unintended operational impacts that may result from such a participation model design change, ensuring to be transparent on any negative impacts to reliability and market revenues for battery storage resources.

 

Settlements

NextEra Energy has questions about how settlement would function in practice. It is NextEra Energy Resources' understanding that the end-of-horizon bid influences dispatch decisions but does not directly settle. If the optimization dispatches the resource in a way that results in a deviation from the operator's intended terminal state-of-charge, it is unclear how that deviation is treated in settlement. Similarly, how real-time deviations from the day-ahead state-of-charge trajectory would be settled when those deviations result from market optimization rather than operator action remains unresolved, as does the interaction with existing imbalance settlement for storage and uplift eligibility. NextEra Energy Resources urges CAISO to develop detailed settlement examples before advancing this concept further.

 

NextEra Energy Resources recommends CAISO defer further development of the storage bidding reframing concept until the design questions identified above are resolved. Instead, CAISO should focus its attention on DEBs and Uplift. If CASO continues to develop the reframing concept, NextEra Energy Resource strongly encourages CAISO to consider implementation and market design questions discussed above.

 


[1] Straw Proposal, p. 39.

[2] Straw Proposal, pp. 44-45.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

 NextEra Energy Resources has no comments at this time.

NV Energy
Submitted 08/05/2026, 03:10 pm

Contact

Rodger Manzano (RodgerJoseph.Manzano@nvenergy.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.
2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.
3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

NV Energy appreciates and supports CAISO incorporating a gas floor in both the time-of-day (TOD) and static approach.  NV Energy also supports CAISO responding to stakeholder feedback and proposing a TOD multiplier equal to or greater than 1.0.  NV Energy still believes that a multiplier less than 1.0 would diminish the DEB for a storage resource and inaccurately rank the storage resource in the resource stack.

NV Energy appreciates CAISO explaining that the TOD will be set 1.4 before the hour that sets the price-based opportunity cost and 1.0 after the hour that set the price-based opportunity cost. However, NV Energy still questions the need for a dynamic TOD multiplier and questions how the TOD multiplier will account for situations when the hour that will set the price-based opportunity cost will occur during the morning ramp of the next day following the evening ramp.  This is of particular concern for storage resources that are use limited.  For example, storage resources that cannot grid charge and can only charge during solar production hours would experience lost opportunity costs if they were mitigated and discharged over evening peak rather than the following morning peak where they may be of more value or needed more for reliability. 

NV Energy suggest that CAISO provide details on how the priced-based opportunity cost scalar is calculated and the range of values for the scalar.

NV Energy has some concerns about setting the charge bid equal to the discharge bid minus variable operating cost.  While setting the charge bid equal to the discharge bid minus the variable operations cost is an easily understandable and transparent concept, it would create a dead band in the bid price range between the charge and discharge DEB where the storage resource would not receive a dispatch.  Additionally, when paired with the proposed multiplier, a large variable operating cost could significantly lower a charge bid and present a scenario where the storage resource does not fully charge before peak periods.  Given the interplay between the proposals, the proposed DEB and the storage default variable operating cost may need to be looked at wholistically.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

NV Energy appreciates CAISO responding to stakeholder feedback and proposing an alternative static approach.  NV Energy supports the use of the static approach given that NV Energy’s main concern centers on storage resources being mitigated to an inaccurate DEB and discharging too early resulting in the storage resource not having the needed state-of-charge over peak periods.  The static approach appears to minimize the opportunities for the storage resource to be mitigated to an inaccurately low level and inappropriately placed in the resource in the bid stack.  NV Energy also believes that the static approach closely mirrors the hydro-based framework and may be easier to implement without the complexities of the TOD approach.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.
6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.
7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

NV Energy is currently unsure if the benefits of a new end-of-hour (EOH) bidding paradigm outweigh the costs from the added complexities.  NV Energy urges CAISO to remain focused on the current storage proposals if CAISO chooses to continue development and discussion on reframing the non-generator resource bidding.  NV Energy believes more in-depth discussions are needed and various details need to be addressed.  For example, how would this proposal affect setting the market clearing price, price formation overall, real-time multi-interval optimization, and DEB and bid cost recovery (BCR) calculation.  Currently storage resources are excluded from BCR eligibility if a scheduling coordinator submits an EOH constraint.  Under this new paradigm, would a storage resource still be excluded from BCR eligibility if a scheduling coordinator were to bid the EOH at a high value.  How would CAISO determine when storage resources would be eligible or excluded from BCR?

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

Pacific Gas & Electric
Submitted 08/05/2026, 02:42 pm

Contact

Todd Ryan (tmrt@pge.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

PG&E appreciates the steady progress CAISO has been making on all the storage tracks. Specific to this straw proposal, PG&E would like to suggest:

  1. The default energy bid methods discussion is making good progress and appears to be on track with the CAISO’s proposed timeline
  2. The state-of-charge management has merits but will not be ready by October and should be in its own paper and on its own timeline.
  3. Both the static and dynamic DEB methods are a step forward from today’s method but PG&E sees more flexibility in the dynamic approach.
2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

PG&E appreciates the progress CAISO has made in this initiative, represented by the straw proposal on Default Energy Bids, Uplift, and State-of-Charge management. We’d like to note that progress is being made on all fronts but that the new designs for a default energy bid for storage and hybrid resources is further along in the process than state-of-charge management topic.

PG&E understands that CAISO is aiming for a final proposal in October of this year.  Given this schedule, it seems unlikely that the state-of-charge management will be ready.  PG&E suggests separate timelines for the further development of these two topics.

 

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

PG&E understands that there are shortcomings to current default energy bid for storage resources including that it is not applicable to energy storage units that do not participate in the day-ahead market (i.e., in a WEIM BAA).  The CAISO has put forward two categories of new methods for calculating a storage DEB:

  1. A static approach – uses a day-ahead power price index as the basis for the DEB.
  2. A dynamic approach – which will dynamically scale a reference price based on the time of day and with changing gas prices.

Regardless of which method which ever DEB is selected, PG&E sees it as a positive step forward that the method will be consistent and applicable across the whole market footprint (DA and RT markets).

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

PG&E believes both represent a step forward from today’s method but PG&E believes that a dynamic approach is likely to provide the flexibility to represent the changing opportunity cost of a storage unit.

PG&E has a few questions:

  • Is there a better method of dynamic scaling than using hour of the day?

While the opportunity cost of the storage resource might correlate highly with hour of the day, it appears to be a proxy for the system demand (or net system demand).  Our intuition is that there might be better exogenous explanatory variables (such as forecasted net-load) that more accurately track the near-term opportunity cost for storage. 

  • What are the power price indices that would be used in the static approach?

Can the CAISO provide a more specific definition of the power price indexes?  Are these primarily based on the bilateral market?

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

PG&E appreciates the level of detail CAISO is considering in the hybrid approach to default energy bids.  Hybrid resources are a unique challenge given the many different configurations: e.g., different generation (solar/wind/thermal), different sizing of the storage relative to the generations, … etc.

We believe CAISO is progressing well on this topic.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

The CAISO is proposing a “greater-of approach”. PG&E understands this to mean that the great of the applicable DEBs would apply to the whole unit.  However, stakeholders have expressed concerns that this could allow a generator to install a trivial amount of storage and then use a higher DEB. Clearly this behavior should not be allowed. CAISO has proposed a minimum share before the
“greater-of approach” should apply.

The storage should be able to meaningfully extend the generation into future hours. PG&E does not have a specific answer but would suggest that it might be helpful to think in terms of duration. The foundation of the proposed storage DEB is that there is an inter-temporal opportunity cost associated with the storage unit saving the energy for future hours. This can only be done with a hybrid unit if generation can be directed into the storage at lower value hours and then meaningfully generate in future hours.  For example, a unit 100 MW solar unit with storage that can inject 100 MWh of energy is equivalent to one hour of generation at the solar’s nameplate capacity. Regardless of whether the storage is actually 100 MW for one hour or 25 MW for four, this equivalent duration might be useful in future discussions.    

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

PG&E is excited to continue to develop this concept with CAISO and sees merit in this new framework.  However, we do not believe it will be ready on the same timeline as the default energy bids. PG&E suggests separating out this to its own timeline.

 

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

PacifiCorp
Submitted 08/05/2026, 01:24 pm

Contact

Vijay Singh (vijay.singh@pacificorp.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

PacifiCorp generally supports CAISO's proposed direction for this initiative. We support advancing storage DEB enhancements as a near-term priority and agree with CAISO's efforts to reduce reliance on stale inputs, improve the representation of storage opportunity costs, and develop a framework that can serve storage resources across the EDAM and WEIM footprints. PacifiCorp generally prefers the time-of-day approach over the static approach, supports continued development of a hybrid DEB framework using the greater-of approach with appropriate guardrails, and supports continued stakeholder discussion of longer-term storage bidding concepts. 

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

PacifiCorp supports CAISO's proposed near-term timeline and sequencing. Prioritizing storage DEB enhancements before broader discussions regarding storage bidding reforms and uplift allows stakeholders to resolve foundational design issues and better inform future discussions regarding storage bidding and uplift reform. 

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

PacifiCorp generally supports the proposed storage DEB enhancements. We agree with CAISO's objective of reducing reliance on potentially stale inputs, improving the representation of storage opportunity costs, and establishing a DEB framework that storage resources can readily utilize regardless of market footprint. 

PacifiCorp also supports efforts to better distinguish charging and discharging DEBs and reduce potential state-of-charge management concerns that may arise when mitigated charge and discharge bids converge.  

PacifiCorp agrees that storage DEB enhancements represent a reasonable near-term priority and can help inform future discussions regarding storage bidding constructs and uplift reform. 

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

PacifiCorp generally prefers the time-of-day approach because it more directly addresses the issues CAISO identified with stale values and changing opportunity costs throughout the operating day. The time-of-day approach also better aligns with CAISO's objective of improving bid-stack positioning under mitigation while creating a readily available DEB framework for storage resources across EDAM and WEIM footprints.   

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

PacifiCorp supports development of a dedicated hybrid DEB framework and agrees that component-level characteristics should inform the calculation.   

PacifiCorp generally supports continued development of the greater of approach with appropriate guardrails. Compared to the largest-component and weighted-average approaches, the greater-of approach appears to better preserve consistency between standalone resources and comparable components within hybrid configurations.  

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

PacifiCorp supports establishing a minimum share requirement as part of the greater-of approach to ensure that a small component does not disproportionately determine the DEB for an entire hybrid resource. At this stage, PacifiCorp does not have a specific recommendation regarding the appropriate threshold. We encourage CAISO to provide additional examples and analysis demonstrating how different thresholds would affect a range of hybrid resource configurations before selecting a final value.  

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

PacifiCorp is interested in continued discussion regarding the concept of reframing non-generator resource bidding and appreciates CAISO initiating early stakeholder dialogue on this topic. At this stage, PacifiCorp would benefit from additional discussion regarding the operational, market optimization, and resource sufficiency evaluation implications of such an approach. Additional examples illustrating potential impacts to resource sufficiency, state-of-charge management, hybrid resource participation, and bidding flexibility would be helpful as stakeholders evaluate the concept. 

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

No additional comments. 

San Diego Gas & Electric
Submitted 08/05/2026, 04:19 pm

Contact

Pamela Mills (pmills@sdge.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

San Diego Gas and Electric (SDG&E) appreciates CAISO's efforts to improve storage design and modeling and to address challenges related to the default energy bid and storage state-of-charge (SOC) management, and offers the following comments on the July 22 meeting and straw proposal.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

SDG&E supports the near-term timeline presented at the July 22 stakeholder meeting. As many stakeholders have reasoned, there is value in prioritizing Storage Default Energy Bid (DEB) reforms before undertaking comprehensive uplift reform.

SDG&E views the MSC-inspired SOC bidding concept as a potentially beneficial long-term enhancement to the storage participation model, but not as an incremental or near-term enhancement. Because it would significantly alter how storage operators manage and bid their fleets, CAISO should allow adequate time for stakeholder evaluation and avoid an accelerated implementation schedule. To that end, it may be necessary to pull that element out of the scope of this proposal or phase it for board approval at a later date. More broadly, SDG&E encourages CAISO to remain flexible as proposals evolve and provide stakeholders with sufficient time to assess impacts and offer meaningful feedback.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

SDG&E prefers the multiplier-based Time-of-Day (TOD) DEB proposal, as it appears most capable of addressing the challenges of the current framework, including stale opportunity cost estimates. If implemented appropriately, the TOD approach should better reflect the changing value of stored energy throughout the day and improve mitigation outcomes for storage resources. However, if the resulting methodology proves overly complex or leads to unexpected or uneconomic dispatch outcomes, SDG&E would prefer a simpler static DEB approach. Regardless of the design, the primary objective should be to accurately reflect storage opportunity costs while preserving logical, transparent, and predictable market outcomes for storage resource operators.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

SDG&E generally supports use of the gas floor in either the TOD or Static DEB framework. While the gas floor is not directly tied to storage costs, it appears to provide a reasonable proxy for replacement energy costs by approximating the cost of serving load with a marginal gas-fired resource when stored energy is discharged. The proposed formulation, which uses the greater of the calculated opportunity cost or the gas floor, appropriately limits its application to periods where it is relevant. However, SDG&E would like to know why the 11,068 MMBtu/MWh heat rate value was used.

SDG&E also supports the objective of better reflecting changing opportunity costs throughout the operating day but has questions regarding the proposed multipliers. SDG&E encourages CAISO to evaluate whether it is possible to do storage-specific analysis to derive more appropriate multipliers for the TOU and Static DEBs. Further, it would be helpful for CAISO to provide a clear summary in the next paper or workshop how these multiplier values were developed, what analysis they were based on, as well as any interdependencies they may have with non-market reference prices, and how that translates for storage resources.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

SDG&E appreciates CAISO's efforts to establish a dedicated DEB methodology for hybrid resources and generally supports the proposed greater-of approach. Compared to the Largest Component and Weighted Average alternatives, the greater-of approach appears better positioned to preserve the opportunity costs of storage and maintain bid-stack positioning that is more consistent with comparable standalone resources under mitigation.

As CAISO continues to develop broader storage DEB reforms intended to better reflect storage opportunity costs, SDG&E encourages CAISO to ensure the hybrid DEB framework remains consistent with those objectives. SDG&E supports continued development of the greater-of approach and encourages CAISO to provide additional analysis demonstrating how the proposal performs across different hybrid configurations and market conditions.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

SDG&E agrees that a minimum share requirement is an appropriate safeguard to ensure that a de minimis storage component does not disproportionately determine the DEB treatment of an otherwise generation-dominated hybrid resource. While SDG&E does not offer a formulation for a threshold value, the minimum share requirement should be tied to the storage component's ability to meaningfully shift the generation from the paired resource across hours rather than a percentage of its installed capacity.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

SDG&E appreciates CAISO's exploration of the non-generator resource bidding concept and agrees with stakeholders such as PG&E, Vistra, and WPTF that the proposal represents a significant departure from the current storage bidding paradigm rather than an incremental enhancement. While the concept may offer long-term benefits through improved SOC management and day-ahead/real-time alignment, important questions remain regarding its impacts.

SDG&E believes additional analysis and stakeholder engagement are needed to better understand how storage resources would express operational preferences and opportunity costs under the proposed framework and whether a single SOC-value bid can adequately replace the existing charge and discharge bidding construct. Accordingly, SDG&E supports continued evaluation of the concept but does not view it as a near-term market enhancement and encourages CAISO to take time to develop this concept before advancing to board approval.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

No further comment. 

Southern California Edison
Submitted 08/05/2026, 03:57 pm

Contact

John Diep (John.diep@sce.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

Southern California Edison (SCE) appreciates the opportunity to provide comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management. SCE’s comments can be summarized as follows: 

Timeline and initiative Sequencing 
SCE does not object to CAISO's near-term timeline and supports prioritizing default energy bid enhancements and state-of-charge management before pursuing a broader uplift redesign.  SCE requests greater clarity regarding whether uplift redesign remains within the scope of this proposal. SCE also requests that CAISO provide stakeholders with updated information regarding bid cost recovery outcomes following last year’s implementation of storage BCR enhancements. This will inform stakeholders as to whether uplift redesign should be postponed. 

Storage Default Energy Bid Enhancements 
SCE supports CAISO's time-of-day default energy bid approach because it more accurately reflects storage opportunity costs and changing market conditions than a static framework.  However, SCE requests additional transparency on the proposed scaling methodology, time-of-day multipliers, and price-based opportunity cost adders, and recommends ensuring the approach remains robust across seasonal conditions, future resource mix changes, and bid cost recovery impacts. 

Hybrid Resource Default Energy Bids 
SCE generally supports the greater-of-approach for hybrid default energy bids with a minimum shared requirement to ensure the selected default energy bid reflects the resources dominant operating characteristics.  SCE also recommends that CAISO evaluate whether this approach is appropriate to use across other hybrid resource configurations, including combinations involving thermal resources. 

Minimum Share Requirement for Hybrid Resources 
SCE recommends that CAISO use market data and resource configuration information to inform any minimum share requirement for hybrid resources. SCE believes market surveys and resource  
distribution analyses can help establish appropriate thresholds while minimizing unintended exclusion of resources and ensuring the selected methodology appropriately reflects diverse hybrid resource types. 

State-of-Charge Management and Non-Generator Resource Bidding Concepts 
SCE supports exploring mechanisms that allow market participants to value stored energy beyond existing optimization horizons, including the optional end-of-day (EOD) state-of-charge parameter in the day-ahead market and further exploration of real-time state-of-charge deviation frameworks. However, SCE is concerned that the EOD state-of-charge bidding parameter could create opportunities for strategic behavior if not carefully designed and therefore recommends that CAISO establish appropriate safeguards and obtain input from both the Market Surveillance Committee and the Department of Market Monitoring prior to implementation. SCE also emphasizes that if an EOD bid parameter is adopted, preserving scheduling coordinator flexibility through the existing bidding paradigm is needed. 

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

SCE does not object to the CAISO’s near-term timeline, including the apparent resequencing that prioritizes default energy bid enhancements and state-of-charge management before a more comprehensive uplift redesign.  SCE supports this sequencing if it allows the CAISO and stakeholders to first develop a more accurate mitigation framework for storage resources, particularly because the default energy bid design may affect downstream uplift outcomes. However, SCE recommends that the CAISO be explicit about whether uplift redesign is within the scope of the final proposal for this initiative or will be deferred to a later phase.  If uplift is deferred to a later phase, then CAISO should consider renaming the straw proposal to only those topics covered throughout the end of the year to avoid confusion.  

SCE also recommends that the CAISO provide updated information on observed bid cost recovery trends following recent enhancements made last year as part of the Storage Bid Cost Recovery and Default Energy Bid Enhancements initiative.  The change would replace charge and discharge bids with proxy values in bid cost recovery calculations if the respective bid is deemed to result in inflated BCR payments. This additional information should help stakeholders assess the implications of deferring the broader uplift redesign while prioritizing default energy bid reforms.  Lower energy storage BCR following the implementation of proxy value rules would give SCE additional confidence in the existing CAISO priority list.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

SCE supports the CAISO’s time-of-day approach for default energy bid formulation because it is more likely to reflect the true opportunity costs faced by storage resources throughout the operating day than a purely static approach. The existing framework relies on values that may be stale and not properly reflect shorter-term market dynamics, particularly in real time and during periods when premature discharge could reduce the availability of storage for later high-value hours.  

SCE supports the objective of using a time-of-day structure to better preserve storage capability ahead of periods when discharge may be most valuable but recommends that the CAISO provide justification for the proposed scaling methodology, time-of-day multiplier values, and 40 percent adder on the price-based opportunity cost. SCE suggests justifying the robustness and appropriateness of the fixed multipliers (i.e., 1.1 and 1.4) over time. In addition, SCE encourages the CAISO to prioritize an approach that remains effective across seasonal conditions, including periods that may have implications for BCR outcomes, and that continues to perform as the resource mix evolves. Such an approach would reduce reliance on market dynamics or characteristics associated with specific resource types, such as gas resources or hydro-based DEB formulations, thereby supporting a more durable and adaptable long-term solution. 

SCE also agrees with the general principle of a dynamic TOD multiplier. SCE emphasizes prioritizing visibility around the formulation of the TOD values and robustness under comprehensive market conditions and as the system evolves. SCE recommends that the CAISO periodically analyze whether resulting default energy bid levels remain consistent with mitigation objectives and whether they could affect bid cost recovery uplift outcomes, particularly if uplift calculations rely on default energy bid values. Expected changes in the load curve over the next decades may necessitate changes in the TOD multiplier structure to ensure that the DEBs achieve their goal of allowing storage resources to be available at the times of most significant needs of the system.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

SCE believes that the static approach should not be pursued any further as it fails to account for changing real-time conditions and local price differences in the opportunity cost calculation.  SCE believes that one overarching goal is to mitigate storage in a manner that better reflects the value of stored energy over time, and a static approach fails to accomplish that.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

SCE generally supports the greater-of approach for hybrid DEBs with a minimum share requirement for solar plus storage hybrid resources. Without a minimum share requirement, a hybrid resource with a very small storage component and a much larger solar component could potentially qualify for treatment that does not reflect the resource’s dominant operating characteristics. The same principle should apply for wind plus storage hybrid resources.  

However, to generalize and use the greater-of approach may not be appropriate for all hybrid combinations. For storage plus gas resources, the primary driver by nameplate is likely the gas side with the storage aspect augmenting technical capabilities. However, under the greater-of approach, this may conflict with the higher DEB value taking effective, especially around the complexity as there is consideration of a dynamic (i.e., varying by hour) storage DEB.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

For a solar plus storage or wind resource, SCE requests that CAISO provide a market-wide distribution of observed battery to solar ratios for all hybrid resources participating in the market. It does not make commercial sense to have, for example, a 1 MW battery with a 100 MW solar facility; therefore, such an outlier configuration should be excluded. A percentile distribution could help inform an appropriate threshold while minimizing the risk of unfairly excluding resources. 
 
For hybrid storage and gas (thermal) resources, SCE recommends a similar approach to conducting a market survey to understand resources’ configurations within the market. The result from the market survey can help inform whether the great-of approach is appropriate or should nameplate capacity be used to determine which DEBs would be used.   

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

Regarding DA, SCE supports a mechanism that allows market participants to value stored energy beyond the optimization horizon as an optional end-of-day (EOD) daily bid parameter. This can take the form of the proposed penalty cost as presented to reflect inter-day opportunity costs. However, SCE is concerned that the EOD bid parameter could create opportunities for strategic behavior such as opportunities to withhold.  For example, market participants may have an incentive to submit inflated penalty values if doing so increases the likelihood that state-of-charge is preserved for future hours when prices are expected to be higher.  If the penalty price parameter materially influences dispatch outcomes, the ISO should include safeguards in the proposal to ensure that submitted values reasonably reflect the economic value of storage energy and do not distort market outcomes. Before any final proposal is approved, the proposal should be evaluation by both the Market Surveillance Committee (MSC) and Department of Market Monitoring (DMM). 

In addition to the EOD daily bid parameter, SCE believes the existing hourly charge/discharge bidding paradigm is sufficient to reflect the intraday arbitrage opportunity cost and is necessary to retain flexibility to reflect complex bilateral contractual costs. As such, a model that detracts from status quo should be opt-in for scheduling coordinators that prefer a simpler participation model. In any implementation, market participants’ approach in determining an appropriate value may lead to market inefficiencies. Considering this, SCE recommends ISO identify metrics that track the implementation of an EOD SOC value parameter to validate its effectiveness over time.? 

Regarding RT, SCE supports further exploration regarding a real-time SOC-deviation bidding framework. Due to the sensitivity to A/S deliverability and implied uplift, SCE recommends CAISO lead with high-key design guidelines when exploring solutions. Similar to DA solutions, SCE would strongly prefer any implementation that retains scheduling coordinator flexibility via optional levers.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

SCE does not have any additional comments.

Terra-Gen
Submitted 08/04/2026, 03:02 pm

Contact

Jake McDermott (jmcdermott@terra-gen.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

Terra-Gen appreciates the work of CAISO in advancing needed reforms to storage DEBs alongside a robust stakeholder process that resulted in several iterations of different DEB formulations. Terra-Gen supports the Time-of-Day (TOD) storage DEB primarily due to its ability to better preserve SOC for evening peak periods (i.e., prevent premature dispatch) and its usage of TOD multipliers between 1 and 1.4. With respect to the hybrid DEB proposal, Terra-Gen prefers the "greater-of" approach among the 3 different options and believes it should not have a minimum share applied at this time. However, Terra-Gen remains concerned that hybrid resource operators are not given clear tools and guidance on how best to manage SOC needs given the disconnect between the tariff and the BPM for market operations. In the absence of needed edits to the market operations BPM that would align dynamic limit usage with the tariff, CAISO should refrain from applying DEBs to hybrid resources.  

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

Terra-Gen is supportive of moving forward with the near-term timeline as discussed at the July 22, 2026 meeting, subject to some qualifications. For the revised straw proposal and draft final proposal due later in the fall, Terra-Gen recommends that CAISO only seek to move forward with a new DEB formulation applied to storage and for CAISO to take more time with the hybrid DEB. The different hybrid DEB options presented at the July 22 meeting are a good start and it’s worth having additional stakeholder conversations and proposal refinements before coalescing around a final hybrid DEB design. By contrast, CAISO has improved the proposed storage DEB options over several stakeholder meetings. That time frame has allowed for useful stakeholder feedback in shaping the final contours of the storage DEB.  ? 

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

Terra-Gen supports the Time-of-Day (TOD) storage DEB over the static storage DEB. While we appreciate CAISO's attempts to provide an additional DEB construct for stakeholder feedback, the TOD DEB formulation attempts to differentiate charge and discharge DEBs through scalars applied to the max of 3 different values: the variable operations cost, price based opportunity cost, and the gas floor. Some of these values are included in the static DEB formulation, but Terra-Gen specifically supports preserving valuable SOC in the periods leading up to the evening peak. This appears easier to accomplish when the DEB can change throughout the day and is structured to prevent premature dispatch in advance of daily peak conditions. Realistically, a DEB that is higher in hours prior to peak periods will better advance this goal. 

 

Additionally, the TOD better solves some of the underlying issues outlined by CAISO, including the "stale" values that permeate the existing DEB. While the TOD DEB does not eliminate the issue, the scaling factors set between 1-1.4 will meaningfully mitigate it. The TOD DEB allows for better placement of storage within the bid stack – another important improvement that Terra-Gen supports. 

 

Terra-Gen recommends that CAISO consider future refinements to the storage DEB that may allow for additional visibility into the next day's real-time DEBs. There are occasional seasonal peaks during early morning hours. In those instances, it may be more valuable for the market to further limit dispatch in the evening peak and save it for the next morning. While Terra-Gen does not have a concrete proposal on this topic, it may be prudent to analyze potential multi-peak period days and how best to structure the multipliers accordingly. 

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

Terra-Gen recommends that if the TOD DEB is implemented, CAISO should track how often each of the three price variables used by the RT DEB (i.e., max of variable operations cost, price-based opportunity cost, and gas floor) binds for both EDAM and WEIM-only resources. Terra-Gen still finds that there should be a single DEB methodology applied across the fleet irrespective of whether the BAA is within EDAM or is WEIM-only. This cannot be reasonably accomplished for WEIM-only resources given that the RT DEB for EDAM is scaled based on the difference between DA and RT LMPs. That said, CAISO should track how often a resource's DEB is set by the different elements and should revisit the DEB formulation later if there's a stark divergence between how similar resources are mitigated based on WEIM-only or EDAM status. 

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

Terra-Gen appreciates the different proposed options within CAISO’s straw proposal along with the numerical examples of how each would function for a range of project configurations. At this time, it is still premature to apply a DEB to hybrids without clearer tools or considerations around managing the SOC for certain configurations. In addition, Terra-Gen is concerned that the DEB formulations contained within the straw proposal do not adequately capture the range of operational costs for hybrids. 

 

Within the March 9, 2026, issue paper and straw proposal on mixed fuel resources, CAISO highlighted that the “market model does not possess the necessary visibility into the operations of the hybrid storage asset, particularly state-of-charge." At the March 16, 2026, stakeholder meeting, CAISO also noted that "hybrids self-optimize and are fully responsible for meeting availability requirements." This self-optimization is done by the scheduling coordinator specifically because CAISO does not directly manage a hybrid's applicable storage component through the imposition of constraints within the market model. This presents a clear challenge for resource owners: scheduling coordinators must self-manage the SOC external to the market model, are responsible for meeting any availability requirements, and now may face bid mitigation down to a DEB. If the CAISO still desires for hybrids to self-manage and optimize SOC through bids, it follows that operators must have bidding flexibility to effectively do so. That bidding flexibility is compromised when a resource is mitigated down to a DEB, and has the market override its own attempts at SOC self-management. 

 

This inconsistency could be solved in 2 different ways: either through revisions that align the BPM with the tariff which provides explicit permission to utilize dynamic limits as a tool to manage a hybrid's SOC, or alternatively, through new market constraints that prevent awards leading to infeasible dispatch instructions later in the day. Terra-Gen prefers and recommends the former approach, as this would align BPMs with the existing tariff language. For example, Sec. 30.5.6.2 (Hybrid Resource Bids) within the tariff concretely describes that SCs "may also use Hybrid Dynamic Limits to manage onsite charging of an energy storage component." The BPM for market operations however only describes scenarios for dynamic limit applicability for "unavailability due to state of charge" or "to reflect onsite charging." The same BPM is further unaligned with the tariff by claiming that "resource operators will need to manage the state of charge of any storage component through typical (Price, MW) bid submissions." 

 

In the absence of providing scheduling coordinators needed tools to manage the SOC for hybrid resources under bid mitigation, CAISO should not apply any existing DEB formulation to hybrids. Hybrid assets are unique in that they may have grid-charging restrictions as conditions of tax credit eligibility. These restrictions are specific operational constraints that are not reflected within either the static or TOD storage DEB. As a result, while many hybrids may combine a VER with a storage system, their operational considerations are quite different than each of their individual components. These differences make it inappropriate to simply apply any existing off-the-shelf DEB to hybrids without accounting for these constraints or aligning the BPM with the tariff with respect to SOC management.  

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

Terra-Gen does not support a minimum share requirement as part of the "greater-of approach" to a hybrid DEB. As discussed during the July 22, 2026, stakeholder meeting, resources were historically built in a hybrid configuration for specific purposes. A key reason for doing so is related to investment tax credit (ITC) treatment for energy storage projects. Before the enactment of the Inflation Reduction Act (IRA), storage projects were only able to access the ITC if they charged from the renewable component of the facility. This is what led to many projects opting for a hybridization approach rather than co-location: hybridization and grid-charging restrictions led to conformity with tax incentive rules.  

 

Within the straw proposal, CAISO highlights its "concerns about whether this methodology would properly mitigate the exercise of market power for some hybrid configurations under certain circumstances...given this potential for misuse, the ISO believes that any application of the greater-of approach should include a minimum share requirement." It is unclear if CAISO's concern centers around the possibility of developers adding a small storage component to what would have been a VER for the purposes of obtaining a higher DEB. If this is CAISO's concern, then a minimum share is not warranted as this is not how developers make decisions around the types of resources and configurations to construct. CAISO's concern around a 100 MW hybrid composed of 99 MW PV and 1 MW storage ignores that during evening hours, the plant would dispatch entirely from its storage component, making the much lower LMP based DEB an inappropriately low bid to mitigate down to. 

 

Instead of establishing a minimum share up front with no data on market outcomes, Terra-Gen recommends that CAISO table this proposal until there is a clear need within the market to establish a minimum share. If that need arises, CAISO can properly flesh out the contour of what an appropriate minimum share would look like and the underlying problem it aims to solve as evideced by market data. Nonetheless, if CAISO does intend to apply a minimum share requirement to any hybrid DEB, Terra-Gen recommends that CAISO investigate the current fleet of operating hybrids and set the minimum share requirement to the smallest percentage share of any individual component level. This ensures that existing assets are unharmed through an after-the-fact DEB imposition. 

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

At this time, Terra-Gen recommends tabling this topic until a later date. This change would starkly alter bidding for storage resources, which may not be advisable given the myriad of other policy topics that CAISO intends to work through in this initiative.  

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

Vistra Corp.
Submitted 08/06/2026, 05:50 am

Contact

Cathleen Colbert (cathleen.colbert@vistracorp.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

Vistra appreciates CAISO’s continued work on storage design and modeling and supports near-term development of the storage DEB and hybrid DEB proposals, provided CAISO gives stakeholders sufficient analysis and implementation detail before finalizing the design. Vistra recommends that CAISO select the Static Approach for the revised storage DEB, modified to incorporate the strongest elements of the Time-of-Day (TOD) proposal, including a scalar to address stale input risk and an empirically calibrated Short-Term Component multiplier documented in the BPM.

While Vistra recognizes that CAISO’s revised TOD proposal is meaningfully improved, Vistra remains concerned that the TOD approach may create false precision by administratively identifying the hour used to establish the price-based opportunity cost and then stepping down the multiplier before the actual discharge hours relevant to the resource’s daily duration. If CAISO proceeds with the TOD approach, it should explain how the design will address premature multiplier step-downs, shoulder-season days with non-continuous discharge hours, and inconsistent opportunity-cost estimates for similarly situated EDAM and WEIM resources.

Vistra also supports CAISO’s greater-of proposal for hybrid DEBs but does not believe CAISO has demonstrated that a minimum-share threshold is necessary. CAISO should adopt the greater-of approach, monitor hybrid resource configurations, and consider a threshold only if observed development practices support such a change. Finally, Vistra does not support advancing the reframed NGR bidding concept in this initiative. Any end-of-hour state-of-charge bidding enhancement should be evaluated separately and designed to supplement, not replace, interval bids needed for dispatch and price formation.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

Vistra supports continued near-term development of the storage DEB and hybrid DEB proposals, provided CAISO gives stakeholders sufficient analysis and implementation detail before finalizing the design. The near-term timeline should not be used to advance the reframed NGR bidding concept. If CAISO continues to explore reframed NGR bidding, it should do so in a separate stakeholder process with a complete problem statement and analysis of bidding, dispatch, and price formation.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

Vistra appreciates CAISO’s presentation of a straw proposal with two alternatives: Time-of-Day approach and Static Approach. Vistra supports the CAISO moving forward with a proposed option between these two in its revised straw proposal expected in early September. The current real-time storage DEB does not always reasonably capture real-time opportunity costs, particularly when real-time market conditions change materially from day-ahead market results. A revised DEB that better reflects the opportunity cost of preserving limited stored energy for discharge hours across the operating day is important for efficient dispatch, price formation, and reliability.

Vistra acknowledges that the TOD Approach in the straw proposal is meaningfully improved compared to the previous version of the proposal. However, we continue to have concerns that the TOD Approach may misrepresent storage opportunity costs and may apply different price inputs or opportunity-cost estimation methods to similarly situated storage resources across EDAM and WEIM. Vistra continues to believe the Static Approach is the superior foundation because it better avoids false precision and can better preserve a resource’s four-hour discharge capability if the Short-Term Component (STC) multiplier is empirically calibrated. Vistra supports CAISO advancing a revised storage DEB proposal in the next iteration, but recommends that CAISO select the Static Approach, modified to incorporate the strongest elements of the TOD proposal.

While Vistra does not prefer the TOD Approach, the simplified TOD proposal is an improvement over prior, more complex designs. Vistra remains concerned that the design may produce a storage DEB that misrepresents its opportunity costs more often than the Static Approach. Vistra has two principal concerns. The approach may step down the multiplier before the hour used to establish the price-based opportunity cost, which appears to be assumed to represent the first discharge hour for the resource. If that hour does not correspond to the fourth-highest priced hour or the actual first discharge hour for the resource, the DEB may not preserve the resource’s four-hour capability as intended. If the lower multiplier applies during midday charging opportunities, the mitigated charging range may not preserve sufficient economic headroom for the resource to acquire state of charge needed for later discharge hours.

Vistra requests the following additional considerations on the TOD Approach before it progresses further.

  1. CAISO should evaluate how often the hour used to establish the price-based opportunity cost does not correspond to the actual nth-highest priced hour or the actual first discharge hour relevant to the resource’s daily duration.
  2. CAISO should provide an explanation for how the TOD Approach would work during a shoulder season day where the highest hours are non-continuous occurring partially in the morning and partially in the evening.
  3. CAISO should consider adopting a consistent price source for similarly situated storage resources across EDAM and WEIM unless CAISO demonstrates that different price inputs are necessary and do not create inconsistent mitigation outcomes.
4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.

The Static Approach has three important advantages over the TOD Approach:

  • First, it may reduce the risk of false precision by establishing a value intended to preserve a resource’s discharge capability for its daily duration without requiring CAISO to precisely identify when the relevant discharge hours will occur;
  • Second, use of an electric trading hub price may better represent broader system opportunity costs where nodal prices are affected by local conditions, congestion, or mitigation outcomes that do not reflect system-wide need; and
  • Third, Third, a common or consistently derived price input would reduce the risk that similarly situated storage resources receive materially different DEBs solely because they participate through EDAM or WEIM.

The TOD Approach appears to have an advantage in that it estimates a scalar to reflect changing conditions over recent days. The TOD Approach continues to raise two concerns:

  • First, the TOD Approach attempts to identify when storage is likely to begin discharging and then steps the multiplier down to 1.0., however if the hour setting the price-based opportunity cost occurs in the morning during e.g., the shoulder-season then this approach could prematurely reduce the TOD multiplier and sustain it through the remainder of the day.
  • Second, the TOD approach may estimate opportunity costs differently for storage resources depending on whether they participate through EDAM or WEIM, even though their relevant operating characteristics do not differ.

Vistra encourages the CAISO to continue improving the Static Approach. The strongest elements of the TOD proposal are its attempt to address stale input risk through a scalar and its expectation that the applicable multiplier would be supported by empirical analysis. CAISO should incorporate both concepts into the Static Approach. First, the CAISO could incorporate the scalar concept by scaling the electricity hub prices by the ratio of the weighted-average Fifteen Minute Market prices across the 16-hour block period over the past three days and its applicable peak index price. Second, the CAISO could update the STC multiplier on a recurring basis that is applied to the scaled Short-Term Component based on empirical analysis performed to initially set the 1.4 multiplier as documented in Local Market Power Mitigation Enhancements Draft Final Proposal,[1] and to document the multiplier in the BPM.

If CAISO pursues the TOD Approach instead of the Static Approach, CAISO should explain why the time-of-day result is more reasonable and how it will address concerns regarding applying the step-down too early, holding the step-down across the middle of the day, and estimating opportunity costs differently between EDAM and WEIM.


[1] See Page 39-42, https://stakeholdercenter.caiso.com/InitiativeDocuments/DraftFinalProposal-LocalMarketPowerMitigationEnhancements-UpdatedJan31_2019.pdf.

5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

Vistra supports CAISO’s greater-of proposal for hybrid DEBs because mitigation should not understate the costs or opportunity costs of a hybrid resource’s underlying components. The proposal is directionally reasonable because it reduces the risk that mitigation will suppress a hybrid resource’s bid below the expected incremental cost of a material component.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

Vistra does not believe CAISO has demonstrated that a minimum-share threshold is necessary. For solar-plus-storage hybrid resources operating as variable energy resources, the stronger incentive is generally to maximize production rather than to exercise supply-side market power through mitigation outcomes. Vistra recommends that CAISO adopt the greater-of approach and monitor hybrid resource configurations before adopting a minimum-share threshold. If observed development practices indicate that new configurations are being designed to circumvent the policy intent of the greater-of framework, CAISO would then have a record to support considering a threshold.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

Vistra does not support advancing the reframed NGR bidding concept in this initiative. CAISO has not demonstrated that the current NGR bidding framework creates a problem requiring this broader redesign, nor has CAISO sufficiently explained how the concept would affect bidding flexibility, dispatch decisions, clearing prices, or interactions with other storage state-of-charge constraints.

Vistra incoroporates our previous comments on the topic by reference here. We reiterate that interval bids remain central to dispatch and price formation. If CAISO believes an end-of-hour state-of-charge value or related bidding concept could improve storage modeling, CAISO should evaluate that concept separately and design it to supplement, not replace, the bidding structures needed for interval dispatch and market pricing.

CAISO should prioritize implementable DEB improvements in this initiative and defer any broader NGR bidding reform to a separate, holistic stakeholder process if it chooses to continue exploring the concept.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.

None currently.

WPTF
Submitted 08/05/2026, 04:30 pm

Submitted on behalf of
Western Power Trading Forum

Contact

Kallie Wells (kwells@gridwell.com)

1. Please provide a summary of your organization’s comments on the July 22, 2026 stakeholder meeting and the straw proposal on Default Energy Bids, Uplift, and State-of-Charge Management.

WPTF appreciates CAISO’s responsiveness to stakeholder feedback. The revised design addresses WPTF’s principal concerns with the earlier, more complex TOD proposal, including unclear multiplier-setting, the potential for counterintuitive price formation, and ambiguity regarding the DEB applied to the charging range. However, CAISO should conduct analysis to determine the hours to which each multiplier applies and establish monitoring for unintended dispatch and pricing outcomes as storage becomes marginal during more hours. The multiplier values and applicable hours should remain in the BPM so they can be adjusted promptly based on market experience. WPTF also generally supports the proposed hybrid DEB framework, but CAISO should analyze the composition of existing hybrid resources before establishing a minimum-share threshold. Finally, WPTF remains unpersuaded that reframing NGR bidding is necessary or an improvement over the current design and does not support advancing that concept at this time.

2. Please provide your organization’s comments on the initiative’s near-term timeline as shared during the July 22, 2026 stakeholder meeting.

WPTF supports continued near-term development of the storage DEB and hybrid DEB proposals, provided CAISO completes the requested analysis and provides sufficient implementation detail. The schedule should allow stakeholders to review the analysis supporting the multiplier hours and hybrid minimum-share requirement before those design choices are finalized. The NGR bidding concept should not proceed because CAISO has not demonstrated that it is needed or would improve upon the current framework.

3. Please provide your organization’s comments on the straw proposal for storage default energy bid enhancements.

WPTF appreciates CAISO’s incorporation of stakeholder feedback in this iteration. WPTF’s primary concern with the earlier TOD proposal was that its complexity could produce counterintuitive price formation without a clear basis for the multiplier values or the hours to which they would apply. The simplified design largely addresses those concerns.

In particular, the revised proposal addresses WPTF’s concerns regarding: (1) how CAISO would establish and apply multiple hourly multipliers; (2) the potential use of multipliers below 1.0 during peak net-load hours, which could cause mitigated storage to set lower prices during peak hours than during midday hours; and (3) the need to clearly define the DEB applicable to the charging range.

WPTF understands that a 1.4 multiplier would apply to all hours before the hour used to establish the price-based opportunity cost, such as the fourth-highest-priced hour, and a 1.0 multiplier would apply thereafter. Limiting the design to multipliers of 1.4 and 1.0 is a reasonable simplification. However, we believe additional discussion should be had to help ensure that the step down to the 1.0 multiplier is done in the most appropriate hour. For example, there could be a case where the 4th highest hour setting the price-based opportunity cost is hour 8 and then hours 19-21 are the next three highest priced hours. Based on the current proposal, the DEB would step down to 1.0 multiplier in hour 7 and remain at that level throughout the rest of the day including the midday hours. WPTF raises this scenario to highlight we should think through how best to set the logic used when determining the hour in which the 1.0 multiplier is applied such that the outcome of the DEB aligns with the intended outcome of the policy effort.

Also, CAISO should monitor how often storage is marginal during hours assigned the 1.4 and 1.0 multipliers and whether the resulting mitigated bids produce counterintuitive price patterns. For example, a $100/MWh base DEB would become $140/MWh in an hour assigned the 1.4 multiplier but remain $100/MWh during a later peak net-load hour assigned the 1.0 multiplier. If storage becomes marginal in both periods, the DEB could support higher prices during the earlier, lower-demand hour than during the peak period. This risk may be limited if CAISO accurately selects the applicable hours, but it could become more significant as storage penetration increases. CAISO should therefore establish monitoring and revisit the multiplier values or hours if these outcomes occur with meaningful frequency.

If the TOD approach is ultimately adopted, the multiplier values and the hours to which they apply should be specified in the BPM rather than fixed in the Tariff. This would allow CAISO to respond promptly to observed market outcomes through the BPM stakeholder process without requiring a new FERC filing for every adjustment.

4. Please provide your organization’s comments on the comparison between the time-of-day and static approaches, whether there are elements of the static approach that should be leveraged in the time of day approach, and whether there are elements of either approach that merit modification.
5. Please provide your organization’s comments on the straw proposal regarding hybrid default energy bids.

WPTF generally supports the proposed greater-of approach for hybrid DEBs. Using the higher applicable component DEB can help avoid understating the costs of a higher-cost component when the hybrid resource is mitigated. However, the approach will only produce reasonable outcomes if the minimum-share requirement does not underestimate the DEBs of each underlying component. WPTF provides more detail on this element in response to question #6 below.

6. Please provide your organization’s comments on how the ISO should determine a minimum share requirement to apply as part of the greater-of approach for hybrid default energy bids.

Establishing the minimum-share requirement is challenging because mitigation applies to the hybrid resource’s full energy bid, not solely to the component that satisfies the threshold. For example, if a 100 MW hybrid contains 10 MW of storage and the minimum share is set at 25 percent, the storage DEB would not be considered and the solar DEB would apply to the entire resource. Because the solar DEB is likely at or near $0/MWh, that result would not accurately reflect the opportunity cost of the storage component, thus underestimating the DEB.

Before selecting a threshold, CAISO should analyze the capacity shares of the underlying components of existing hybrid resources and provide stakeholders with an aggregated summary. Although the market may not have access to this information, CAISO may have it through interconnection or registration data. The threshold should be informed by the observed resource configurations and tested against representative examples to ensure it does not systematically exclude a material storage or thermal component. For example, if the analysis shows that the higher-cost component generally represents at least 25 percent of hybrid capacity, a 25 percent threshold may be reasonable; otherwise, CAISO should consider a lower threshold or another safeguard.

7. Please provide your organization’s comments on the discussions questions regarding the concept of reframing non-generator resource bidding.

WPTF remains unpersuaded that reframing NGR bidding is necessary or would improve upon the current modeling and bidding design. CAISO has not demonstrated a material problem that the concept would solve or sufficiently explained the effects on bidding flexibility, dispatch, mitigation, and settlement. WPTF therefore does not support advancing the concept at this time.

8. Please provide any additional comments, feedback, or examples. You can upload supporting materials using the attachments field below.
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