Comments on Uplift & DEB, State-of-Charge Management, and Mixed-Fuel and Distribution-Level Resources Meeting on Sep 29, 2025

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

Boston Energy appreciates the opportunity to provide feedback on the ongoing policy discussions affecting storage resources in CAISO markets. Our comments are primarily focused on the CAISO providing stakeholders with clarity on the outage management process for storage resources subject to distribution level charge constraints.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

Boston Energy's only comment at this time is to say that removing day-ahead BCR for a certain resource type, but not others should be thoroughly discussed with stakeholders to ensure that storage resources aren’t experiencing financial losses based on CAISO market inefficiencies or out of market actions.    

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

Boston Energy has no comments at this time.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

Boston Energy has no comments at this time.

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

Boston Energy has no comments at this time.

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

The guidance provided by CAISO on which nature of work outage cards not to use when reporting distribution-level charging constraints is important information for Scheduling Coordinator (SC's). However, it is equally important for CAISO to clarify which specific outage cards should be used in these situations.

SC's need clear instructions on how to accurately reflect these restrictions through the outage card process. We ask the CAISO to provide additional guidance so that SC's can appropriately report such outages moving forward.  

Last, Boston Energy is concerned with the CAISO’s approach of providing such important guidance within a 78-page policy presentation.  It’s clear from the presentation that ISO is expecting SC’s to take action immediately.  Burying this directive in the middle of a policy presentation has the possibility to be missed by stakeholders.  Boston Energy would have expected the ISO to issue a market notice to all stakeholders or at a minimum reach out directly to SC’s with distribution level constrained assets to make sure they are aware of the ISO’s position.       

7. Provide your organization's comments regarding the SOC Management Topics

Boston Energy has no comments at this time.

8. Provide your organization's comments regarding the PRR 1627 Changes

Boston Energy has no comments at this time.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

Boston Energy has no comments at this time.

10. Are there alternative methods to calculate solar HSL that you recommend?

Boston Energy has no comments at this time.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

Boston Energy has no comments at this time.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

Boston Energy has no comments at this time.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

Boston Energy has no comments at this time.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

The California Community Choice Association (CalCCA) appreciates the opportunity to comment on the September 29, 2025, Working Group meeting (WG Meeting). The comments herein recommend that the CAISO:

• Adopt the stakeholder-supported, principle-based approach of “determining the actor that caused negative revenues,” rather than a blanket elimination of day-ahead bid cost recovery (BCR);
• Require the submission of the day-ahead initial state-of-charge (SOC) parameter within a certain accuracy range to be eligible for BCR and ensure the accuracy range is set conservatively enough such that the parameter cannot be used to inappropriately inflate BCR payments;
• To fully understand the impacts of out-of-merit dispatches, provide stakeholders with data on the BCR cost impacts due to out-of-merit dispatches when they occur;
• Clarify that the transmission-induced nature-of-work is not an appropriate outage card to reflect routine charging constraints and provide guidance on which nature-of-work should be used to reflect these charging constraints; and
• Provide in its next update on proposed revision request (PRR) 1627 changes, data on the changes in cost to the market before and after the implementation of the PRR.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

CalCCA supports the CAISO eliminating opportunities for strategic bidding to inflate BCR payments and agrees with the stakeholder-supported, principle-based approach focused on “determining the actor that caused negative revenues.”[1] The CAISO’s solution should adhere to this principle, rather than instituting a blanket elimination of day-ahead BCR, unless the CAISO can demonstrate all cases of day-ahead BCR are driven by scheduling coordinator action rather than CAISO market or operator action.

CalCCA also directionally supports the CAISO’s proposal to require the submission of the day-ahead initial SOC parameter within a certain accuracy range to be eligible for BCR. In general, scheduling coordinators should be responsible for accurately reflecting their resources’ characteristics rather than relying on a default value. The CAISO, in consultation with the Department of Market Monitoring should ensure the accuracy range is set conservatively enough such that the parameter cannot be used to inappropriately inflate BCR payments.

[1]            CAISO Slides, at 10.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

CalCCA appreciates the data provided by the CAISO regarding the performance of CAISO storage resources under the multi-interval optimization and is encouraged by the low frequency of out-of-merit dispatch. To fully understand the impacts of out-of-merit dispatches, however, the CAISO should provide stakeholders with data on the BCR cost impacts due to out-of-merit dispatches when they occur. This data will help inform stakeholders of whether the instances of out-of-merit dispatches have a material impact on the costs to load.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

CalCCA has no comments at this time.

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

CalCCA has no comments at this time.

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

During the WG Meeting, the CAISO stated that it has observed distribution-level resources using the “transmission induced” outage nature of work to reflect charging constraints associated with the charging distribution service chosen by the resource during the interconnection process. The CAISO stated that resources should not use the transmission induced outage nature of work to reflect routine charging constraints. CalCCA agrees with the CAISO that the transmission-induced nature-of-work is not an appropriate outage card to reflect routine charging constraints given the distribution resource elected to interconnect where potential charging constraints exist.

The CAISO did not, however, provide guidance on which nature of work should be used to reflect these charging constraints. Clear outage reporting requirements are necessary for resources to provide the CAISO with transparency on resource charging constraints and availability. The CAISO should therefore continue to work with stakeholders to provide this clear guidance.

7. Provide your organization's comments regarding the SOC Management Topics

CalCCA has no comments at this time.

8. Provide your organization's comments regarding the PRR 1627 Changes

CalCCA appreciates the CAISO’s continued monitoring and reporting of PRR 1627 changes. In its next update, the CAISO should provide data on the changes in cost to the market before and after the implementation of the PRR. If possible, the CAISO should perform a counterfactual analysis comparing what the costs would have been under the previous calculation methodology compared to the actual costs after the implementation over the same time period, so that market participants can fully understand the impacts of the change.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

CalCCA has no comments at this time.

10. Are there alternative methods to calculate solar HSL that you recommend?

CalCCA has no comments at this time.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

CalCCA has no comments at this time.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

CalCCA has no comments at this time.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

CalCCA has no comments at this time.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

The California Energy Storage Alliance (CESA) appreciates the opportunity to comment on the September 29, 2025, Storage Design and Modeling working group.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

CESA does not support eliminating day-ahead bid cost recovery (BCR) for storage as an independent market design change. CESA continues to support a holistic review of a necessary make-whole payment design when shortfalls are caused by CAISO market limitations and storage operator actions. CAISO has highlighted that “forced” buy-backs and sell-backs for day-ahead energy schedules in the real-time market are the primary drivers of storage BCR. Thus, there is an interaction between the two markets when determining the appropriateness of a make-whole payment. CESA believes this initiative should focus on a real-time make-whole payment for storage leveraging the conceptual framework CESA provided earlier.     

The key principle regarding a new storage real-time make whole payment design is whether the shortfall was caused by the storage operator or caused by CAISO market shortcomings.  CESA’s conceptual framework is to eliminate forced buyback (sellback) hours (from highest to lowest) from the make-whole settlement for each hour the storage operator is dispatched using energy bids inconsistent with real-time conditions. At the September 29 working group, CAISO proposed an accuracy threshold for the day-ahead initial state of charge (ISOC) bid parameter to be eligible for real-time BCR or any successor paradigm. A similar approach could be applied to the ISOC. If the ISOC used in the day-ahead market were lower by the amount the resource could be charged in a given operating hour, then the highest forced buyback hourly shortfall would be excluded from the real-time make whole calculation. CESA looks forward to CAISO developing a proposal consistent with the conceptual framework.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

CESA appreciates the data provided by the CAISO regarding the accuracy of the real-time multi-interval optimization. The current BCR design developed for thermal resources considers start-up costs, minimum load costs, and energy bid costs when calculating an interval’s shortfall. Energy bid cost shortfalls are not the primary driver of real-time BCR for thermal resources but are the single driver of the need for a real-time make whole payment for storage. Out-of-merit dispatches in approximately 10% of intervals seem to justify a real-time make-whole payment for storage. Currently, the out-of-merit dispatches could result in a real-time BCR payment for storage resources.  During the working group, CESA requested the CAISO provide data on how often other resource types are dispatched out-of-merit based on the resource’s energy bid.

While CAISO summarized that RTD binding intervals are comparable to advisory interval prices, there are some outliers observed during the morning peak. CAISO also stated that schedules between binding and advisory intervals are generally comparable. Outliers are why a make-whole payment is necessary. If the outlier causes a storage resource to not cover its costs over the day, the storage resource deserves a real-time make-whole payment.

CAISO’s summary of the impact of out-of-merit dispatch understated the potential impact on a storage resource and the need for a real-time make-whole payment. While storage resources receive out-of-merit dispatches in less than 10% of intervals, it seems very high and could be materially higher than other resource types. Likewise, while ~84% of storage resources have less than 10% of out-of-merit dispatches, that means ~16% have greater than 10% out-of-merit dispatches. Given the level of out-of-merit dispatches for some resources, a real-time make whole payment is needed. CAISO should also seek to understand the root causes of the out-of-merit dispatches to determine if market design enhancements are necessary.

Lastly, the CAISO summarized that a higher frequency of out-of-merit dispatches was observed during the summer months and in afternoons (HE14-17). This is potentially concerning if storage resources are not being dispatched consistent with the resource’s discharge and charging bids just prior to the evening net peak. Given the potential reliability issues this could create, CAISO must determine the root causes behind this observation.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

In general, CESA supports reasonable requests by CAISO to enhance telemetry and other resource information that will improve the CAISO dispatch of resources. During the working group, CAISO mentioned that the iHSL proposal would apply to all solar resources. If this is the case, CAISO should discuss this change with a broader stakeholder group than those in this initiative focused on improving the hybrid model. 

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

No additional comments. 

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

CESA does not support using a nature of work that is not exempt from the resource adequacy availability incentive mechanism (RAAIM) for WDAT storage resource subject to distribution charging constraints. CESA supports including the charging restrictions placed on WDAT storage resources in the Master File. If these operational constraints were modeled in the optimization, there would be no exposure to RAAIM penalties. Until the operational constraints are modeled, WDAT storage resources should continue to use an outage nature of work that exempt from RAAIM penalties. 

First, it is illogical to subject storage resources to RAAIM penalties if the CAISO’s ultimate goal is to introduce new Master File parameters to adequately reflect distribution-level charging restrictions in the market optimization. The CAISO is unjustified in applying a RAAIM penalty for a near-term solution when once the operational characteristic is included in the market model there would be no outage subject to a RAAIM penalty.

Second, if the CAISO has issues with the calculation of qualifying capacity (QC) developed by the CPUC, CAISO should engage in a CPUC process and not inappropriately apply RAAIM penalties the purpose of which is NOT to validate QC calculations.

CAISO attempted to justify its position by arguing that WDAT storage resources made this decision by not choosing Firm charging service. This was not a viable choice for resources interconnecting with SCE. SCE requires that resources fund all upgrades to resolve all N-1 contingencies, which is an unreasonable expectation of a project developer. In addition, the static charging tables are intended to be an interim solution put in place until SCE can deploy a sub-transmission level constraint management system (CMS). SCE currently estimates that this system will be completed in Q2 of 2027. CESA notes that the CAISO’s security constrained economic dispatch (SCED) enforces N-1 contingencies in the market and does not penalize storage resource not dispatched to charge because a constraint is binding.  This further justifies using a RAAIM exempt nature of work during this interim period.

During the working group, a stakeholder asked CAISO what nature of work should be used for charging constraints. CAISO was unable to or unwilling to answer this question during the working group. If CAISO does not believe that “transmission induced” is the correct nature of work, should the resource use the “technical limitations not in the market model” nature of work?  CAISO should clarify publicly for all stakeholders how to reflect distribution charging constraints since the CAISO currently is unable to model these operational limitations and not subject to RAAIM penalties. 

7. Provide your organization's comments regarding the SOC Management Topics

CESA reiterates that complete documentation of the storage modeling constraints in the integrated forward market, residual unit commitment process, fifteen-minute market, and real-time dispatch are needed to perform a holistic review of storage participation in the CAISO markets.  CESA first raised the value of this in comments provided January 8, 2025, and heard agreement with the value proposition. However, after 10 months, what should have been the starting point for effective and efficient improvements to conditions giving rise to the need for real-time make whole payments, the documentation has still not been developed.  

CESA appreciates briefly discussing the changes to the Day-Ahead Market Enhancements business requirements specification regarding the envelope equations in the working group. However, CESA is becoming increasingly concerned with the proliferation of attenuation factors and the impact to storage dispatch and overall price formation by distorting opportunity cost calculations. CAISO must closely monitor the inefficiencies caused by including attenuation factors based upon forecasted usage which will always be wrong. CAISO should also plan to review its findings with the Markets Surveillance Committee.   

8. Provide your organization's comments regarding the PRR 1627 Changes

CESA appreciates the regular updates regarding the performance of FRU since the product was added to the state-of-charge constraints with attenuation factors. CAISO noted that there have been seven instances of negative FRU prices. This is concerning because it is further evidence that the SOC with attenuation factors is undermining price formation by incorrectly calculating opportunity costs between charging/discharging energy and other products. CESA looks forward to additional discussion in the working group on the resolutions the CAISO is considering internally.    

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

No additional comments. 

10. Are there alternative methods to calculate solar HSL that you recommend?

No additional comments. 

11. Provide your organization's comments on the presentation offered by the Fluence Energy

CESA appreciated the presentation by Fluence Energy. The presentation highlighted the need for storage operators to consider the state of charge, state of balance, and state of health of the underline storage technology to optimize bidding and participation in the CAISO markets. CESA notes that the presentation highlights the willingness of storage operators to maximize the capabilities of their resource, if the CAISO rules create incentives to do so.   

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

CESA appreciated the presentation by GridSME on behalf of Wellhead Power Services. Wellhead has developed a resource combination of a gas turbine and energy storage located at the same point of interconnection using either hybrid market model. The proposal to use the higher of the variable fuel cost option or the storage default energy bid illustrates a point CESA highlighted in the Price Formation Enhancements Rules for Bidding above the Soft Offer Cap.  In that initiative, CESA highlighted the need to correctly position storage in the bid stack to avoid dispatch inconsistent with real-time system conditions. The proposal outlined by Wellhead is aligned with CESA position how to improve default energy bids for storage. 

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

No additional comments. 

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

Comments on Storage Design and Modeling

Working Group Presentation on September 29, 2025

Department of Market Monitoring

October 14, 2025

Summary

The Department of Market Monitoring (DMM) appreciates the opportunity to comment on the Storage Design and Modeling working group presentation dated September 29, 2025.[1]

DMM appreciates the ISO’s attention to storage bid cost recovery (BCR) issues. DMM continues to support eliminating day-ahead (DA) BCR for storage resources unless specific instances are identified where DA BCR is clearly appropriate for storage resources. The ISO and stakeholders have not demonstrated that day-ahead BCR for storage resources is necessary to support market efficiency. Further, the current DA BCR design for batteries can lead to unwarranted BCR payments and is susceptible to gaming.

DMM recommends a similar approach to establishing real-time (RT) BCR eligibility for storage resources, with a default of no BCR, and eligibility for RT BCR is only provided under specific situations when it is deemed appropriate. This would address market efficiency issues created by the current RT BCR design for batteries, and would also solve other issues, including unwarranted RT BCR due to inaccurate DA initial state-of-charge (ISOC) parameters. If the ISO instead chooses to individually address each scenario that could lead to unwarranted RT BCR, DMM supports the proposals to require and incentivize accurate submissions of the DA ISOC parameter. DMM notes that even if the DA ISOC is accurate, there is still a bidding incentive issue if storage resources receive BCR for day-ahead buybacks due to insufficient state-of-charge.

DMM appreciates the ISO’s analysis indicating there is a low frequency of the market dispatching storage resources uneconomically. DMM continues to urge stakeholders to consider the overall benefits of multi-interval optimization (MIO), as an uneconomic dispatch in one interval may allow the storage resource to earn greater profits in future intervals. DMM’s analysis presented in these comments finds that batteries earn greater net energy revenues as the result of MIO, compared to schedules that are only driven by prices in the binding interval.

Developing DEBs for hybrid resources should be a relatively high priority. Currently, hybrid resources are not subject to local market power mitigation (LMPM). These resources should be subject to LMPM, and the ISO should develop an expedited default energy bid (DEB) approach to estimate the resources’ marginal costs. The DEB for hybrid resources can then continue to be enhanced as needed in future initiatives.

DMM supports the ISO’s direction to distribution-level resources to not use a “transmission induced” outage to reflect their distribution system charging constraints. DMM recommends further enhancements for the resources to reflect their charging limitations in the market and through the outage management system (OMS).

Comments

DMM supports battery BCR only where appropriate and necessary to support market efficiency

DMM supports the ISO addressing storage bid cost recovery issues as a top priority. DMM supports the ISO’s proposal to eliminate DA BCR for storage resources as there has yet to be any demonstration of DA BCR for storage resources being necessary to promote market efficiency or incentivize efficient bidding. In addition, DMM has found the vast majority of day-ahead BCR for storage resources arises from uneconomic schedules due to parameter submissions by the scheduling coordinators.[2],[3] As mentioned in previous comments, DMM recommends redesigning storage BCR rules to assume no eligibility, and only add eligibility under specific situations where it is deemed appropriate and necessary to support market efficiency.[4] If the ISO elects to maintain any DA BCR eligibility for batteries, DMM recommends the ISO or stakeholders provide examples or detailed scenarios where DA BCR is necessary to support market efficiency to justify incorporating these scenarios into the DA BCR framework.

DMM recommends the same bottom-up approach be taken to establish rules for real-time bid cost recovery for batteries. The current real-time bid cost recovery rules remove the exposure to real-time prices for storage resources with day-ahead schedules, which incentivizes these resources to submit real-time bids that are inconsistent with estimated real-time intraday opportunity costs, and can result in inefficient dispatch of storage resources in the real-time market.[5] DMM recommends the ISO determine which scenarios warrant RT BCR for storage resources and eliminate RT BCR in all other instances.

DMM supports stronger incentives to submit accurate day-ahead initial state-of-charge

As DMM has previously noted, allowing real-time bid cost recovery for day-ahead buybacks due to insufficient state-of-charge (SOC) can lead to inefficient bidding and market outcomes. In addition to creating inefficient real-time bidding incentives, the current BCR design can also disincentivize submission of accurate DA ISOC values. This can lead to schedules that may be infeasible in real-time, and therefore can lead to increased levels of unwarranted BCR for day-ahead buybacks. The day-ahead ISOC parameter may be inaccurate because battery operators submit estimates that are not likely to materialize, or because battery operators fail to submit an estimate and the default of zero is different than the telemetered state-of-charge at the beginning of the operating day. DMM supports the ISO’s proposals to address the current lack of incentive for storage resources to submit accurate DA ISOC parameters.

DMM supports the ISO requiring the submission of the DA ISOC in order to submit DA bids, especially if the ISO inserting a default value for any missing submissions would be used as justification to provide BCR when the ISO’s default value is inaccurate. DMM believes that it would be more efficient if stakeholders were incentivized to submit accurate DA ISOC estimates. DMM recommends the ISO consider that this could be achieved by removing RT BCR for DA buybacks due to insufficient SOC. DMM would also support a proposal to incentivize more accurate ISOC estimates by making battery resources ineligible for RT BCR if their day-ahead ISOC is substantially different than their telemetered ISOC at the beginning of the operating day. However, DMM notes that even if resources submit accurate DA ISOC estimates, continuing to provide RT BCR for day-ahead buybacks due to insufficient SOC still results in inefficient bidding incentives and inefficient dispatch of storage resources in real-time.  

Multi-interval optimization provides benefits that exceed the cost of uneconomic dispatches

Stakeholders have raised concerns about uneconomic dispatches of storage resources driven by the multi-interval optimization, which considers prices in advisory intervals when providing dispatch instructions to resources in the binding interval. DMM has recommended analyzing both the benefits and costs of the multi-interval optimization (MIO) prior to considering whether or not the ISO should provide uplift to storage resources for the uneconomic dispatches that may occur as a result of MIO.[6]

DMM appreciates the ISO’s analysis on the frequency of uneconomic dispatches of storage resources, which found that 80 percent of storage resources were dispatched uneconomically in less than 10 percent of intervals.[7] While this analysis provides some insight into the potential costs associated with MIO, the discussion has yet to focus on the potential benefits of MIO.[8] By considering prices in advisory intervals, a storage resource may receive an uneconomic dispatch in one interval that allows them to earn higher profits in future intervals.

To provide more insight into the benefits of the multi-interval optimization, DMM modeled a counterfactual of battery schedules based solely on the economics in the binding interval. DMM compared each unit’s schedule under this counterfactual “no MIO” model to the actual market schedules for each unit under MIO. Using these two schedules, along with locational marginal prices (LMPs), we can estimate the net energy revenues under the two different outcomes and compare them to assess the potential benefits of MIO.

It is important to note that this counterfactual does not account for many of the other reasons that dispatches in the binding interval may be uneconomic. The counterfactual solely accounts for resources’ bids, LMPs, state-of-charge, and ancillary state-of-charge constraint. As such, the counterfactual may imply schedules that are not feasible due to other reasons and could therefore over-estimate counterfactual profits that would occur without MIO. Currently, this analysis only calculates counterfactual schedules for the fifteen-minute market (FMM) and compares estimated FMM net energy revenues based on actual and counterfactual FMM schedules and FMM LMPs.

To demonstrate the importance of considering the benefits of MIO, we analyze the same storage resource on the same day highlighted by NextEra in the June 30^th working group presentation.[9]^,[10] Figure 1 shows the actual schedule (dotted blue line) and the counterfactual schedule (orange line) of this resource on March 19, 2025, the day it received the uneconomic dispatch discussed in the presentation. During this presentation, NextEra noted this particular storage resource received an uneconomic schedule to discharge in hour-ending 17, which can be seen by the dotted blue line in Figure 1. Comparing the two schedules indicates that while the counterfactual schedule does not result in the uneconomic dispatch in hour-ending 17 or the other uneconomic dispatch in hour 22, it also does not schedule the resource to charge in hour-ending 18 or discharge in hour-ending 23. Figure 2 shows the FMM LMPs of this resource on this day, and it indicates that the deviations in hour-ending 18 and 23 allowed the resource to earn greater profits in those intervals.

By using the LMPs across this day, DMM estimates that the unit’s net energy revenues from the actual MIO schedule are 8 percent higher than the net energy revenues based on the unit’s counterfactual no-MIO schedule. This is a conservative estimate for the benefit of MIO on this day, as there may be other limitations on the battery that may be affecting the actual schedule that are not accounted for in the counterfactual. This example highlights the importance of considering more than just an uneconomic dispatch in a single interval, because that dispatch may position the battery to earn more profits later in the day – by either charging at a more negative price or discharging at a more positive price.

Figure 1              Actual and Counterfactual Schedule of Battery Resource on March 19, 2025

Figure 2              FMM LMPs of Battery Resource on March 19, 2025

DMM extended this analysis to calculate the estimated daily net energy revenues for all storage resources in the FMM based on both their actual MIO schedule and the counterfactual no-MIO schedule and relevant FMM LMPs. Specifically, the analysis included 138 CAISO storage resources from October 2024 to September 2025 that were on-line by the start of the sample period. This analysis is an initial exercise and is intended to introduce an approach that measures not only the costs of MIO but the benefits as well. The analysis currently does not consider schedules or revenues in the day-ahead or five-minute (RTD) market. All numbers reflect estimated settlement of the resource’s FMM schedule only on FMM prices.

Figure 3 compares the distribution of daily net energy revenues for the actual schedules with the daily net energy revenues for the counterfactual schedules. Table 1 provides some additional statistics on these distributions. The analysis indicates that overall, battery resources are very likely to earn higher net energy revenues from the MIO compared to market solutions that only consider the economics of the binding interval.

Figure 3. Distributions of net energy revenues estimated for MIO vs. non-MIO schedules

Table 1.  Distribution of estimated daily net energy revenues for MIO vs. non-MIO schedules

Daily net energy revenues from schedules using the MIO are 24 percent higher than net energy revenues from the counterfactual no-MIO schedules. In addition, the distribution of daily net energy revenues of actual schedules has a much longer tail of positive profits. This indicates that there is a higher probability of realizing some more extreme profits under the MIO that the resources would miss out on otherwise. This result is intuitive, as the MIO may optimize resources in the binding interval to capture upcoming price spikes that appear first in advisory intervals and may not be anticipated in the expectations of future prices that inform resource bids in the binding interval. 

As noted above, this initial analysis is intended to establish a more complete assessment of the potential costs and benefits of MIO, extending the focus beyond individual intervals that may result in uneconomic dispatch. The results here provide a conservative estimate of the benefits of MIO and further refinements could improve the accuracy of the counterfactual. DMM will leverage this framework and continue to refine the analysis to further demonstrate the costs and benefits of the multi-interval optimization.

DMM supports mitigation of hybrid resources with an easily implementable default energy bid that can be enhanced in future initiatives

DMM continues to place a high priority on subjecting hybrid resources to local market power mitigation. This requires first developing a default energy bid for hybrid resources. To subject hybrid resources to local market power mitigation, in the near term DMM supports calculating a DEB for hybrid resources using the maximum of the DEBs that apply to each of the generation components that make up the hybrid resource. In cases where the resource is paired with storage, the DEB would often be driven by the opportunity cost of the storage component.[11] This initial approach should be easy to implement and should achieve the goal of subjecting hybrid resources to local market power mitigation in the near-term. After a near-term solution for hybrid DEBs is implemented, hybrid resource DEBs should continue to be enhanced to more accurately reflect the costs of hybrid resources as a full system of different generation components.

DMM has previously recommended the hybrid DEB vary hourly for hybrids with storage components.[12] The DEB for hybrids with a storage component should follow the hourly storage DEB enhancements as proposed by DMM for storage resources.[13]

In addition to future enhancements to allow hourly variation, hybrid resource DEBs should leverage the existing CAISO DEB structure that allows resources to have multiple bid segments in the DEB curve. This may be appropriate as hybrids can have underlying technologies with potentially very different marginal (or opportunity) costs. In hybrid configurations with hybrid components such as natural gas and storage, the opportunity cost of the storage resource may far exceed the variable costs of the natural gas component. In cases like this, for operational ranges where the storage resource is not being dispatched to increase the output of the hybrid resource beyond the operation of the gas resource, the DEB should reflect the cost of the lower cost of the gas resource, and not the higher opportunity cost of the storage resource.

As the storage DEB is being enhanced in this stakeholder process, DMM supports using the current storage DEB in the interim for hybrid resources with a storage component to subject hybrid resources to some degree of mitigation. However, DMM recommends the ISO and stakeholders discuss potential issues with using the current storage DEB for hybrid resources, and consider these issues in the ongoing refinements of a DEB for hybrid resources in the future.

DMM supports improved transparency and modeling of distribution-level charging constraints; DMM supports the ISO’s guidance that “transmission induced” outages are not the appropriate tool to reflect these constraints

Distribution-level resources have unique charging characteristics, and DMM continues to recommend the ISO identifying these resources in Master File. Further, DMM recommends the ISO develop a long-term solution to distribution-level resources to manage the unique constraints. A key element of the long-term solution DMM recommends is improvement to transparency of the charging limits imposed on distribution-level resources from the distribution system operator (DSO) tariffs.

In the near term, the ISO has directed resources to continue to reflect these limitations through OMS, and instructed resources not to use the “transmission induced” outage card.[14] DMM has previously observed distribution-level resources using these outages and brought this issue to the attention of the ISO. DMM agrees the transmission induced outage card is inappropriate for distribution-level charging constraints that are known constraints of the resource’s interconnection, and not the result of an outage on the transmission or distribution system. DMM encourages the ISO to provide guidance to the market participants on the correct outage card type to use in the interim, and develop a long-term solution to managing these constraints. 

DMM recommends the ISO develop a lasting solution to managing and monitoring distribution-level charging constraints. In the forthcoming OMS enhancements, DMM continues to recommend the ISO include a unique outage card type that reflects these limitations. The transmission induced outage card is exempt from the resource adequacy availability incentive mechanism (RAAIM). The distribution-level charging constraint limitation should not be exempt from RAAIM because this limitation is known in advance of the development of the resource, and not a result of a transmission or distribution equipment outage. As the ISO considers development of a unique outage card for these constraints, it too should not be RAAIM exempt, or exempt from any potential future mechanism to incentivize RA availability.

Given the nature of the constraints, DMM recommends the ISO pursue a policy that allows distribution-level resources to reflect their limits with as little latency as possible. As DMM has previously noted, this could potentially be achieved through the use of dynamic limits by distribution-level resources, but only if they are registered in Master File as distribution-level resources, and only if there is sufficient data available for monitoring the use of such limits.[15]^,[16] If dynamic limits were to be used for this purpose, DMM recommends considerations for resource adequacy be thoroughly contemplated, as DMM has discussed in previous comments.[17]

[1] Working Group on Uplift & DEB, SOC Management, and Mixed-Fuel & Distribution-Level Resources presentation, California ISO, September 29, 2025: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

[2] Comments on Storage Bid Cost Recovery and Default Energy Bids, Department of Market Monitoring, July 18, 2024: https://www.caiso.com/documents/dmm-comments-on-storage-bcr-and-default-energy-bids-july-8-2024-workshop-jul-18-2024.pdf

[3] Comments on Storage Design and Modeling Working Group Session 1, Department of Market Monitoring, January 8, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-working-group-session-dec-11-2024-jan-8-2025.pdf

[4] Comments on Storage Design and Modeling May 28, 2025 Presentation, Department of Market Monitoring, June 11, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-may-28-2025-presentation-jun-11-2025.pdf

[5] Comments on Storage Design and Modeling June 30, 2025 Presentation, Department of Market Monitoring, July 16, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-jun-30-2025-working-group-presentation-jul-16-2025.pdf

[6] Comments on Storage Design and Modeling June 30, 2025 Presentation, Department of Market Monitoring, July 16, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-jun-30-2025-working-group-presentation-jul-16-2025.pdf

[7] Working Group on Uplift & DEB, SOC Management, and Mixed-Fuel & Distribution-Level Resources presentation, California ISO, September 29, 2025, slide 33: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

[8] It is important to remember that there are a variety of other reasons besides economics in advisory intervals that can result in uneconomical dispatches.

[9] NextEra Presentation – CAISO Storage Design and Modeling Initiative, NextEra Resources, June 30, 2025, slide 5: https://stakeholdercenter.caiso.com/InitiativeDocuments/NexteraPresentation-StorageDesignandModeling-Jun30-2025.pdf

[10] DMM received consent from NextEra to present additional analysis of this example resource in an anonymized    fashion.

[11] Comments on Storage Design and Modeling June 30, 2025 Presentation, Department of Market Monitoring, July 16, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-jun-30-2025-working-group-presentation-jul-16-2025.pdf

[12] Ibid.

[13] Comments on Storage Design and Modeling Working Group Session 2 and 3, Department of Market Monitoring, March 7, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-working-group-sessions-2-and-3-mar-07-2025.pdf

[14] Working Group on Uplift & DEB, SOC Management, and Mixed-Fuel & Distribution-Level Resources presentation, California ISO, September 29, 2025: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

[15] Comments on Storage Design and Modeling Working Group Session 2 and 3, Department of Market Monitoring, March 7, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-working-group-sessions-2-and-3-mar-07-2025.pdf

[16] Comments on Storage Design and Modeling June 30, 2025 Presentation, Department of Market Monitoring, July 16, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-jun-30-2025-working-group-presentation-jul-16-2025.pdf

[17] Ibid.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

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. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

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. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

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. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

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. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

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. Provide your organization's comments regarding the SOC Management Topics

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. Provide your organization's comments regarding the PRR 1627 Changes

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.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

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.

10. Are there alternative methods to calculate solar HSL that you recommend?

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.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

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.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

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.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data 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.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

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) September 29, 2025 meeting on CAISO’s Storage Design and Modeling Initiative[1] and CAISO’s Draft Straw Proposal on Day-Ahead (DA) Bid Cost Recovery (BCR) for Storage.[2]

Cal Advocates provides the following comments on the September 29, 2025 meeting:

• Cal Advocates supports CAISO’s Draft Straw Proposal to eliminate DA BCR for storage resources.
• Cal Advocates supports CAISO’s Draft Straw Proposal to require storage operators to submit initial DA state-of-charge (SOC) parameters.
• CAISO should conduct an analysis of the overall impact of Multi-Interval Optimization (MIO) on storage revenues that includes both revenue gains and revenues loses due to MIO.

[1] CAISO, Working Group on Uplift & DEB, SOC Management, and Mixed-Fuel & Distribution-Level Resources, September 29, 2025 (September 29 Workshop).  Materials available at: https://stakeholdercenter.caiso.com/StakeholderInitiatives/Storage-design-modeling.

[2] CAISO, Working Group on Uplift & DEB, SOC Management, and Mixed-Fuel & Distribution-Level Resources (September 29, 2025 Workshop Slides) at 11-13.  Available at: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

Cal Advocates supports CAISO’s Draft Straw Proposal to eliminate DA BCR for storage resources.[1]  CAISO analysis shows that the “vast majority” of DA BCR to storage results from uneconomic schedules due to scheduling coordinator (SC) bid parameter submissions,[2] which indicates that most DA BCR payments result from operator action and thus should be ineligible for BCR.[3]  CAISO elimination of DA BCR would be effectively equivalent to adoption of a principle-based approach that would disallow DA BCR for conditions related to operator action rather than CAISO market design.  CAISO elimination of DA BCR provides a straightforward and effective approach to protect ratepayers from unwarranted DA BCR costs.

Cal Advocates also supports CAISO’s Draft Straw Proposal to require SCs to submit initial DA SOC parameters to be eligible for real-time (RT) BCR.[4]   SCs currently have the option but are not required to submit an initial DA SOC.[5]  Currently, if the SC does not submit an initial DA SOC, CAISO sets the initial DA SOC to a default value of zero.  A default value of zero may be inaccurate and lead to uneconomic dispatch and associated BCR under CAISO’s current DA BCR rules. 

SC submission of more accurate initial DA SOC estimates based on telemetry and available market information will likely improve the DA scheduling process and market efficiency and would obviate potential RT BCR resulting from inaccurate initial DA SOC parameters.  Cal Advocates agrees with CAISO that a requirement to submit an initial DA SOC to be eligible for RT BCR would incentivize SCs to provide an accurate SOC value and to use available bidding tools to reach the submitted initial SOC.[6]  

More accurate CAISO market parameters provide benefits to ratepayers from resultant improvements in market efficiency. Cal Advocates supports CAISO’s proposal to require SCs to submit accurate initial DA SOC parameters combined with CAISO’s proposal to eliminate DA BCR.

[1] September 29, 2025 Workshop Slides at 11.

[2] September 29, 2025 Workshop Slides at 11.

[3] See CAISO, Working Group on Outage Management, Uplift & DEB, and Mixed-Fuel & Distribution-Level Resources, August 14, 2025 (August 14 Workshop Slides) at 53.  Available at: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Aug14-2025.pdf.  CAISO indicates that most stakeholders support a principle-based approach to BCR focused on determining the actor that caused negative revenues   If the resource does not recover its costs due to SC action, BCR is not warranted.

[4] September 29, 2025 Workshop Slides at 13.

[5] The Department of Market Monitoring (DMM) has previously stated that current BCR rules fail to incentivize storage SCs to provide accurate estimations of their initial DA SOC.  DMM, Storage Design and Modeling: Storage Bid Cost Recovery, June 30, 2025 at 2.  Available at: https://stakeholdercenter.caiso.com/InitiativeDocuments/DMM-Presentation-Battery-BCR-Discussion-Jun-30-2025.pdf.

[6] September 29, 2025 Workshop Slides at 14.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

CAISO’s analysis of storage operation under the RT MIO process shows that, with some outliers, RT prices in binding intervals are generally consistent with advisory interval prices, and that CAISO RT storage schedules in the binding interval are comparable to storage schedules in the advisory intervals.[1]  CAISO’s analysis also shows that binding internal out-of-merit dispatch happens in less than 10 percent of the binding intervals.

However, as noted in the workshop, out-of-merit dispatch in the binding interval may result either in revenue gains or revenue losses over the trading day.[2]  Thus out-of-merit binding interval dispatch does not correlate to overall MIO-related revenue loss.  If RT prices in the binding interval are generally consistent with advisory prices, as CAISO analysis shows, on balance it would be expected that MIO would have a neutral impact on storage revenue.  If CAISO continues to use RT BCR to compensate MIO-related revenue loss but not account for MIO-related revenue gain, storage may accrue long-term unwarranted revenue to the detriment of ratepayers.

In addition to the price and schedule analysis CAISO provided in the September 29 Workshop, CAISO should conduct an analysis of the overall impact of the MIO on storage revenues, including both revenue losses and revenue gains.  

During the workshop, several participants recommended CAISO consider a more detailed analysis of outliers in the RT binding and advisory price data.[3]  CAISO should not change market rules based on the existence of a few rare observed outliers, and should not assume market conditions caused those outliers.  There will always be outliers in any real-world data.  In statistical terms, sampling on outcomes is a fraught way to learn about causal effects.  Just because an outlier is observed and was exposed to unusual market condition A or B, it does not mean that the market conditions caused the outlier.  If CAISO presents this outlier analysis, it should make very clear whether the market conditions caused the outliers, or if the analysis only presents correlations.  CAISO should not base any policy decision on non-causal patterns.

[1] September 29, 2025 Workshop Slides at 17.

[2] September 29 Workshop Recording, available at: https://www.youtube.com/watch?v=jx6uXvjXW34 at 1:33:30.

[3] September 29 Workshop Recording at 1:20:20.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

Cal Advocates does not have comments at this time. 

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

Cal Advocates does not have comments at this time. 

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

CAISO reminded SCs that, under CAISO’s Business Process Manual (BPM) for Outage Management, it is not appropriate for SCs to use transmission-related outage cards to reflect distribution-level charging constraints.[1]  Storage operators have the option to contract for various levels of charging service from distribution operators, and thus charging-related outages are under the control of storage operators.[2]  Cal Advocates agrees with CAISO that SCs should follow the specified operational and reporting requirements in the CAISO BPM.

[1] September 29, 2025 Workshop Slides at 57.

[2] September 29, 2025 Workshop Slides at 53.

7. Provide your organization's comments regarding the SOC Management Topics

Cal Advocates does not have comments at this time. 

8. Provide your organization's comments regarding the PRR 1627 Changes

Cal Advocates does not have comments at this time. 

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

Cal Advocates does not have comments at this time. 

10. Are there alternative methods to calculate solar HSL that you recommend?

Cal Advocates does not have comments at this time. 

11. Provide your organization's comments on the presentation offered by the Fluence Energy

Cal Advocates does not have comments at this time. 

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

Cal Advocates does not have comments at this time. 

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

 Cal Advocates does not have additional comments at this time. 

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

esVolta, LP (“esVolta”) appreciates the opportunity to comment on the September 29, 2025, Storage Design and Modeling Working Group Presentation. These comments are limited to the sole issue of a proposal for changes to outage reporting codes for distribution-level charging constraints. esVolta continues to support current CAISO practices, recognizing that restrictions imposed by transmission providers based on arbitrary and non-transparent determinations that are beyond our control are appropriately reflected on outage cards as a transmission-induced generation outage and thus RAAIM exempt.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

esVolta continues to support and encourage CAISO to follow its official stakeholder process and vet proposed revisions to CAISO initiatives and the Business Process Manual or any contemplated changes, for example, the Storage Design and modeling Initiative, under the “Working Group Session 9: Uplift and Default Energy Bids (DEB), State-of-Charge Management, and Mixed-Fuel and Distribution-Level Resources” effort.

esVolta contends that it is evident that any inclusions in an opt-in webinar presentation do not constitute official market notice of business practice changes, operational changes, emergency information sharing, etc.  While we appreciated the opportunity to preview options CAISO  is considering at the September 29^th working group meeting, many times only a small subset of market participants attend or are even aware of such convenings. As a result, only select market participants will view or be aware of any unofficial CAISO considerations. The mere fact that CAISO is requesting stakeholder feedback on the “proposals” shared in “Working Group Session 9: Uplift and Default Energy Bids (DEB), State-of-Charge Management, and Mixed-Fuel and Distribution-Level Resources” indicates that CAISO is only floating proposals that it may be contemplating.

Requesting stakeholder feedback is one of the first steps to properly following processes and procedures for making changes to established market practices, business practice manual change that have been Board-approved, such as how storage resources have been reflecting charging restrictions in outage cards.  Many energy storage resources in CAISO have followed the practice of selecting “transmission-induced outage” to reflect charging restrictions imposed by transmission providers that are beyond the storage resource’s control. esVolta contends this classification adequately represents the actions of the transmission provider and the captive nature of the energy storage resource in complying with charging restrictions imposed that change periodically based on determinations of the transmission provider.

The September 29, 2025 Storage Design & Modeling (SDM) Working Group Slide Deck states that resources “should not use the transmission-induced generator outage” to reflect “routine” charging limits. CAISO should continue to allow energy storage resources that are limited by charging constraints imposed by transmission providers to use the Transmission-Induced outage category. These outages are not “routine” and are changed frequently depending on congestion or line limitations and are completely outside of the control of the resource itself. CAISO acknowledged that these restrictions are currently reported through OMS and that the ISO needs transparency on such constraints: an implicit recognition that the operational characteristics are not yet modeled in the market. It is only appropriate that any “official” changes would be accompanied by a CAISO market-wide notice or notification.

esVolta continues to support the current CAISO practice of recognizing that charging restrictions imposed by transmission providers based on arbitrary, non-transparent, and changing determinations that are beyond our control are accepted and reflected on outage cards as a transmission-induced generation outage and thus RAAIM exempt. Further, the CAISO Board’s perspective on this related issue is very informative in the 2018 CA ISO Transmission Induced Outage White Paper:

“The Board-approved policy adopting RAAIM was that “resource outages will be excluded from the availability incentive process if an outage is beyond the resource’s control.” The CAISO now acknowledges that this transmission-induced generation outages caused by planned and CAISO-approved transmission outages should also be considered RAAIM exempt.”

Until CAISO provides a modeled solution, these resources should continue using a RAAIM-exempt nature of work for distribution-imposed limits. Penalizing storage with RAAIM during a bridge period would be neither just nor reasonable, and it conflicts with the September 29 framing that these limits are “routine” and tied to distribution service selection rather than equipment outages. 

Accordingly, esVolta urges CAISO to not make any changes to the use of transmission induced for a charging constraint that is outside the control or knowledge of an energy storage resource operator. Further, CAISO should (1) memorialize any outage-coding direction via Market Notice instead of verbal guidance; (2) model distribution-level charging limits so OMS workarounds are no longer needed; and (3) in the interim explicitly authorize a single RAAIM-exempt outage code for distribution level charging restrictions. This path aligns incentives, preserves compliance certainty, and avoids punitive outcomes for constraints outside of the resource’s control and that the ISO itself has yet to model. 

7. Provide your organization's comments regarding the SOC Management Topics

8. Provide your organization's comments regarding the PRR 1627 Changes

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

10. Are there alternative methods to calculate solar HSL that you recommend?

11. Provide your organization's comments on the presentation offered by the Fluence Energy

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

NextEra Energy Resources (Energy Resources) appreciates the CAISO’s transparency and responsiveness to stakeholder input into the Storage Design and Modeling Initiative. We commend the CAISO for establishing a working group process to work through the various, complex problem statements raised in the initiative.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

Energy Resources generally supports incentives to make submitted day-ahead initial SOC values as accurate as possible to yield an efficient day-ahead market solution. However, Energy Resources questions the value of making the day-ahead initial SOC parameter mandatory and imposing new penalties for deviations between planned and actual day-ahead initial SOC values.

For one, CAISO should not underestimate the complexity that storage operators face in forecasting this initial SOC value ahead of the operating day and how much of the complexity originates from CAISO market processes including market power mitigation, MIO dispatch, Flexible Ramp Product awards, the envelope constraints that will be used to procure Imbalance Reserves in the future, and Regulation attenuation factors. These CAISO processes can all cause a storage resource’s SOC to differ significantly from the initial SOC value the resource submitted in the day-ahead market despite being largely beyond the storage operator’s control.  

Second, although CAISO noted that storage resources have tools like the End of Hour SOC bidding parameter for meeting their submitted or default day-ahead initial SOC values, it is unclear whether increased use of such tools is truly a desirable outcome if it results in outcomes such as the storage fleet aggressively discharging before midnight to align with their default 0 MWh day-ahead initial SOC values. With respect to the End of Hour SOC parameter specifically, Energy Resources notes that use of this parameter would effectively require the storage resource to sacrifice BCR eligibility in the current real-time interval in exchange for preserving BCR eligibility for a future day-ahead interval.

Moreover, Energy Resources is skeptical that mandatory submission and strict penalties for inaccuracy are necessary in the first place. If CAISO’s goal is to make the day-ahead solution as accurate as possible, Energy Resources would argue that storage resources already have sufficient incentives in the form of buyback risk. A resource is only eligible to receive BCR if it realizes a net loss in a given market on a given trade date. Therefore, unless a resource is deliberately engaging in gaming behavior to purposefully realize a net loss and inflate BCR payments, the resource is effectively exposed to buyback risk. If the problem lies with storage resources not submitting day-ahead initial SOC values and the default 0 MWh values being inaccurate, Energy Resources believes changing this default to telemetered SOC in hours 8 and 9 prior to the day-ahead market close could be a reasonable improvement. However, if in CAISO’s view the problem continues to lie with gaming behavior and excessive BCR payments, Energy Resources believes existing market monitoring and enforcement mechanisms (not to mention the increased scrutiny resulting from this stakeholder initiative) are sufficient deterrents.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

Energy Resources thanks CAISO for the extensive effort undertaken to begin understanding how MIO impacts the storge fleet. These preliminary results confirm that OOM dispatch is far from a rare occurrence for storage resources. Energy Resources cautions that while CAISO’s findings indicate 80% of storage resources are affected by MIO less than 10% of all RTD intervals, this does not mean MIO is insignificant. Indeed, even a 1% frequency can have significant impacts – positive or negative – on a storage resource’s net revenues depending on the size of the resource and the delta between the resource’s economic offer and the binding LMP.

Energy Resources reiterates its suggestion during the September 29^th meeting that CAISO expand its analysis to:

(1) Include instances of OOM idling (i.e., MIO dispatches to sit idle at 0 MW when the resource was economic to either charge or discharge), which according to Energy Resources’ analysis appears to be the most frequent form of MIO dispatch; and

(2) Estimate the overall net financial impact of MIO on the storage resource revenues.

In previous presentations to this working group, Energy Resources highlighted instances of apparent sub-optimal MIO dispatch drawn from its own operational experience. Energy Resources remains hopeful that MIO is fulfilling its intended purpose and positioning storage resources (based on advisory price forecasts) better than storage operators themselves are able to do with limited information, thereby improving both storage revenues and market efficiency. However, this has yet to be borne out by CAISO’s analysis or Energy Resources’ experience. Energy Resources looks forward to continued discussion of CAISO’s analysis and reiterates that if CAISO cannot conclusively demonstrate that MIO is an unequivocal net positive for storage operators, storage operators should be entitled to compensation for MIO-driven losses beyond their control.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

Energy Resources believes CAISO's proposed irradiance-based high sustainable limit represents a significant technical advancement that is implementable with proper planning. The f(PAIRD) formulation demonstrates mathematical rigor, and CAISO's presentation examples clearly show how iHSL can bridge the gap between telemetry and irradiance data to deliver more accurate forecasting. This is particularly evident in challenging scenarios like ramping periods and supplemental energy dispatch situations where traditional HSL methods struggle.

Successful implementation requires recognizing the operational complexity involved. Resource owners will need adequate time to calibrate the critical mathematical relationships between irradiance and telemetry that are unique to each facility. The monthly calculation of saturation points and slope parameters demands careful validation across diverse operating conditions.

Most importantly, the industry must avoid rushing implementation. Resource owners need to test and tune these algorithms across their fleets, followed by sufficient lead time for fleet-wide scaling. The integration with existing Follow DOT protocols and supplemental energy dispatch systems requires careful coordination to prevent operational conflicts.

Without this measured approach, Energy Resources foresees risks including forecast accuracy degradation during transitional periods, dispatch optimization conflicts, and potential revenue impacts.

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

No comments.

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

No comments.

7. Provide your organization's comments regarding the SOC Management Topics

No comments.

8. Provide your organization's comments regarding the PRR 1627 Changes

No comments.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

No comments.

10. Are there alternative methods to calculate solar HSL that you recommend?

No comments.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

No comments.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

No comments.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

CAISO and the CPUC have simultaneously advanced multiple initiatives that will reduce the "showable" capacity of storage resources—including CPUC's UCAP methodology refinements, CAISO's marginal ELCC + historical availability framework, and updated outage guidance. While CAISO has explicitly recommended that resource owners address these capacity reductions through oversizing and augmentation to outpace natural degradation, the organization's own Material Modification Assessment (MMA) process cannot accommodate the resulting workload.

At the October 8, 2025, New Resource Implementation Fair, CAISO acknowledged that its MMA process is overwhelmed and operationally constrained. Energy Resources has directly experienced these delays, which create an untenable situation: as capacity measurement becomes more restrictive, the very solutions CAISO recommends become administratively unavailable due to process bottlenecks. Energy Resources believes this creates a regulatory paradox where the CAISO’s policy direction does not match its administrative reality, and the consequences place contractual capacity obligations at risk.

Energy Resources requests CAISO consider improvements to the MMA process that offer expedited review protocols for capacity maintenance projects, standardized pre-approval for common augmentation scenarios, and risk mitigation provisions that protect resources undertaking good faith enhancement efforts. These process improvements would benefit all stakeholders—enabling CAISO to achieve its capacity optimization objectives while providing resource owners viable pathways to maintain contractual compliance. Without immediate action, the disconnect between policy intent and administrative capacity will undermine grid reliability and create unnecessary commercial risks.

Energy Resources stands ready to collaborate on implementing these essential process enhancements.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

PG&E supports improvements in storage modeling and emphasizes the need for deeper analysis and transparency across multiple areas.

• Day-Ahead BCR for Storage: PG&E recommends retaining the automated Day-Ahead BCR process and expanding exclusions to include initial SOC settings that may lead to uneconomic dispatches.
• Performance Under Multi-Interval Optimization: PG&E recommends CAISO to investigate localized forecast errors that may cause systematic losses for certain battery resources.
• Outage Reporting for Distribution-Level Charging Constraints: PG&E supports CAISO’s outage clarification but calls for deeper analysis and tools to improve battery charging reliability.
• SOC Management Topics: PG&E requests a documented process for hourly envelope factor updates and clarification on the basis for hourly variation.
• PRR 1627 Changes (Negative Prices): PG&E requests a focused discussion on negative prices, including their validity, implications for capacity awards, and consequences of non-performance.
• Alternative Methods to Calculate Solar HSL: PG&E supports HSL simplification and advocates for automated CAISO calculations using solar resource inputs.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

PG&E recommends preserving the existing automated BCR framework. If any gaming opportunities or design flaws are identified, they should be addressed through targeted design fixes or temporary disqualification of the involved resources, rather than dismantling the entire process.

• Looking ahead, CAISO is experiencing a rapid increase in battery storage installations. In this evolving landscape, maintaining an automated BCR process is indispensable. The current analyses rely on historical data and may fail to capture emerging trends or future operational complexities. While removing an automated process may seem administratively simple, reestablishing it later would be time-consuming and disruptive.
• While CAISO and previously DMM have presented analyses indicating that batteries generally do not incur BCR in the Day-Ahead market, it is important to recognize that the qualification for BCR is based on whether a resource loses money over the course of a trading day. This does not account for cases where a resource incurs losses during specific intervals due to infeasible dispatches. A deeper, interval-level analysis is necessary to uncover such instances and understand their implications.
• PG&E recommends retaining the automated Day-Ahead BCR process and enhancing evaluation criteria for excluding losses due to effective self-scheduling. Specifically, initial SOC settings that force charge/discharge should be added to existing self-scheduling excluded from DA BCR.  If there are other cases, CAISO should describe them.  Note that the concern with initial SOC is not the discrepancy between forecast and actual, but whether the initial SOC interacts with other parameters, in particular max and min bid in SOC limits and clearances, to produce out-of-the-money dispatches.
  • The discussion around bid-in or CAISO-determined initial SOC versus actual SOC is relevant to Real-Time BCR, not Day-Ahead BCR.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

PG&E urges CAISO to examine whether certain resources are unfairly impacted by localized effects, and to disclose these findings to promote fair and transparent market outcomes.

• CAISO’s analysis sets a reasonable baseline: CAISO’s Market-Informed Optimization (MIO) performs well on average and is widely recognized as a model for real-time dispatch. However, the key issue that needs further attention is the extent to which individual batteries experience losses—both actual financial losses and missed opportunities—due to forecast errors in MIO that manifest locally rather than globally.
• PG&E is particularly interested in understanding whether specific resources are systematically disadvantaged by these localized effects. If so, what are the defining characteristics of those resources? For example, are they tied to particular locations, operational constraints, times of day or year, or specific market conditions? Identifying such patterns is critical.
• If localized losses are found to be frequent or systematic, they present a strong case for considering make-whole or BCR payments to affected battery resources. PG&E encourages CAISO to investigate and disclose these dynamics to ensure fairness and transparency in market outcomes.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

No comment.

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

No comment.

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

PG&E agrees with CAISO’s clarification about what qualifies as a transmission induced outage, while reserving judgment as to the bright line between controllable and uncontrollable restrictions on charging.  CAISO appears to put the entire burden of expectations on batteries that it also intends to treat as critical reliability resources.  PG&E recommends a more detailed analysis of the nature of charging restrictions for batteries located behind distribution constraints. Even if CAISO’s treatment of such outages remains unchanged, PG&E encourages the development of tools to support more dependable battery charging.

7. Provide your organization's comments regarding the SOC Management Topics

PG&E reiterates its request for a documented business process for the calculation and updating of the hourly envelope factors, independent of or in addition to discussion of the topic in the EDAM parameters working group.  PG&E also requests clarification of whether hourly variation in the values would be based on risk levels, historical dispatch levels, or both, noting that because Imbalance Reserves and Reliability Capacity awards to batteries allow bidding of real time energy at any level (subject to RT LMPM), historical dispatch levels are likely shaped by past bidding strategies and hence would not be forecastable as truly independent variables might be.

8. Provide your organization's comments regarding the PRR 1627 Changes

PG&E recommends a dedicated presentation focused solely on the meaning and implications of negative prices. Specifically, we seek clarification on three key points:

1. Are there circumstances in which negative prices are appropriate, and others where they may be considered erroneous or invalid?
2. Does CAISO view nonzero capacity awards at negative prices as meaningful in certain situations?
3. If so, what are the consequences for resources that fail to fulfill awards issued at negative prices?

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

No comment.

10. Are there alternative methods to calculate solar HSL that you recommend?

 PG&E appreciates and agrees with the proposed simplification of HSL submissions. However, PG&E continues to advocate for viewing the proposal as a foundation for enabling automated CAISO calculations of HSL, based on solar resources providing the necessary inputs, rather than exclusively using it to suggest how the derived values should be calculated.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

No comment.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

No comment.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

No comment.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

PGE appreciates the opportunity to participate in this stakeholder group and requests that the CAISO clarify which working group topics are relevant to EIM and future EDAM entities, and, conversely, clearly identify when a topic applies solely to the CAISO balancing authority area.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

While PGE’s current participation is limited to the real-time market, the topic is pertinent for future EDAM readiness. PGE agrees with WPTF and others that the CAISO should defer elimination of day-ahead BCR for storage resources until additional evaluation and alignment across markets are achieved.

However, PGE could also support a phased or conditional approach including deferred implementation until the DAME envelope constraints are active and the CAISO has defined objective criteria for distinguishing market optimization error from operator behavior. Likewise, establishing a reasonable accuracy threshold for initial SOC submission as a prerequisite for any residual BCR eligibility would also help ensure fairness and consistency across balancing areas.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

PGE appreciates the CAISO’s analysis on storage performance under multi-interval optimization and the effort to quantify the frequency of out-of-merit dispatches. However, based on operational experience, the CAISO’s assurances that such dispatches have minimal impact are not yet apparent to PGE.

When a resource receives an unexpected or uneconomic dispatch operating target, there is little visibility into whether it stems from advisory-interval positioning, forecast assumptions, or other modeling factors. PGE requests that the CAISO provide additional explanatory data to demonstrate how and why the current MIO design is functioning as intended, including examples of advisory-interval behavior that illustrate the trade-offs between short-term economics and forward feasibility. Greater transparency on these mechanisms would help EIM and future EDAM entities assess potential effects on real-time settlements, uplift attribution, and operational confidence.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

7. Provide your organization's comments regarding the SOC Management Topics

8. Provide your organization's comments regarding the PRR 1627 Changes

PGE recognizes that system trends following implementation of PRR 1627 have remained stable and appreciates the CAISO’s continued monitoring and analysis of storage resource performance under the revised SOC formulation.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

10. Are there alternative methods to calculate solar HSL that you recommend?

11. Provide your organization's comments on the presentation offered by the Fluence Energy

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

PGE encourages additional discussion on the modeling of fuel types for hybrid resources. Under the current CAISO framework, hybrid resource configurations are limited. As hybridization continues to evolve, market participants are exploring multi-technology configurations that better optimize multi-fuel hybrid resources (for example, a wind farm co-located with solar and battery storage).

To better represent the physical and operational characteristics of these emerging hybrid configurations, PGE recommends that the CAISO consider expanding its hybrid resource model to allow for more fuel types. This enhancement would improve alignment between the Master File and the actual configuration of hybrid facilities, promote accurate market participation, and ensure that the modeling framework remains compatible with the region’s increasingly diverse generation fleet.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

REV Renewables (REV) appreciates CAISO continuing to move ahead on this initiative and provide data analysis to support discussions. As noted below, REV does not support removing Day-Ahead (DA) Bid Cost Recovery (BCR) and requests a more holistic review of BCR. REV also requests more information on Multi-Interval Optimization (MIO), and notes the data provided indicate a potentially concerning trend.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

REV does not support removing DA BCR for storage at this time. While the reasons for DA BCR may be limited, CAISO should not move forward with eliminating before it does a more holistic review of BCR for storage. This review should include DA and real-time (RT) situations so as to avoid unintended consequences.

REV also does not agree with requiring the submission of the DA ISOC parameter to be within a given range of accuracy (e.g., +/- N%) as a prerequisite for eligibility for RT BCR or any successor paradigm. The financial exposure of any error in submitted DA ISOC and realized SOC across midnight of the operating days is fully owned by the resource owner and shouldn’t carry any extra burden.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

REV appreciates the MIO data analysis provided; it is a very helpful starting point for further analysis and discussions. At a minimum, this data analysis indicates a need to maintain RT BCR, especially given that it may have a disproportionate impact on some storage resources. REV requests future RT BCR discussions include consideration of whether the 24-hour horizon for BCR is appropriate for storage. For example, if MIO out of merit dispatch leads to a 50% reduction in revenue for the storage resource for the day, but the resource is technically revenue positive for the day, is that a reasonable outcome? Or in a more extreme example, out of merit dispatch could remove nearly all earnings for the day but the resource still has $10 revenue for the day, is that a reasonable outcome?

REV offers the following requests and observations:

• The increasing frequency of out of merit dispatch from MIO is concerning. CAISO data shows this out of merit dispatch mostly occurs during the early morning and evening net peak when storage resources are needed most, but MIO may not allow them to position themselves to meet CAISO’s need. Additionally, data show the frequency is increasing in summer 2025 compared to summer 2024; CAISO brought online several gigawatts of storage during this time which indicates it may be an increasing problem for storage and the CAISO market.
  • Over 15% of resources (~2 GW) have out of merit frequency of greater than 10%. Some resources experience up to 17% out of merit dispatch. To put this in perspective, this means CAISO could be giving out of merit dispatches for 2.4 hours a day (10% of the day). While CAISO highlighted most resources have less than 10% out of merit dispatch, flipping this data seems to show a potentially concerning picture, though it would be helpful to understand how this compares to other resource types.
• Request for more data analysis –
  • How does performance of storage in MIO compare to other resource types?
  • CAISO provided binding vs. advisory data for system marginal energy cost (SMEC), but how would this look at a nodal level when based on Locational Marginal Price (LMP)? Resources are settled based on LMP and not SMEC, so this view would be helpful.
  • What are the most common reasons for out of merit dispatch?
  • What is the net revenue impact to storage resources from MIO?
    • REV acknowledges MIO may help resources, but it is unclear if MIO helps more than hurts or vice versa.
    • While CAISO highlights RTD SMEC binding vs. advisory intervals were ±$10, this could be a deal breaker for some resources on revenue for the day given increasingly thin price spreads in the CAISO market.
  • Does this indicate need to tweak or eliminate MIO?
    • MIO was initially created to be able to position resources that needed time to ramp up to be available. However, given the market has a large and growing storage fleet that is extremely responsive, does CAISO still need MIO to position resources? Or could CAISO move to a spot market that settles every 5 minutes, as is done in several other markets including ERCOT and SPP? REV highlights that additional market products already exist, including Imbalance Reserves and Flexible Ramp, that could solve for uncertainty in the market.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

REV has no comment at this time. 

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

REV has no comment at this time. 

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

REV has no comment at this time. 

7. Provide your organization's comments regarding the SOC Management Topics

REV has no comment at this time. 

8. Provide your organization's comments regarding the PRR 1627 Changes

REV has no comment at this time. 

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

REV has no comment at this time. 

10. Are there alternative methods to calculate solar HSL that you recommend?

REV has no comment at this time. 

11. Provide your organization's comments on the presentation offered by the Fluence Energy

REV has no comment at this time. 

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

REV has no comment at this time. 

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

REV has no comment at this time. 

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

San Diego Gas and Electric (SDG&E) appreciates the opportunity to comment on the September 29 Storage Design and Modeling stakeholder meeting. SDG&E’s comments are provided within the subsequent questions.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

Through this initiative, CAISO has reviewed and identified potential drivers for storage bid cost recovery (BCR) to determine instances where these payments are warranted. While we agree that there are far fewer instances of DA BCR overall, we believe any changes to the BCR rules must follow a uniform conceptual framework, regardless of whether they apply to the day-ahead or the real-time. It is SDG&E’s position that if a forced buy-back or sell-back of energy is the result of the CAISO market optimization, the storage resource should be eligible for a make-whole payment. To that end, SDG&E opposes broad language which disqualifies all DA BCR on the basis that storage resources in the day-ahead do not warrant uplift, since storage resources in the day-ahead may still be subject to negative revenues attributable to actions outside a SC’s control.

SDG&E agrees that day-ahead self-schedules and uninstructed deviations should not be eligible for a make-whole payment because these actions are in the control of the storage SC. CAISO’s market design should not provide incentives for resources to manipulate their bids or operations such that they receive unwarranted compensation that is not aligned with the intent of BCR.

SDG&E supports exploring methods to improve the accuracy of DA initial state-of-charge (SOC) by either modifying the default value or incentivizing SCs to provide accurate SOC information, within a reasonable threshold. Like the development of the BCR framework, any proposed reporting requirements should be forward-looking and consider how the evolution of the market, such as the introduction of imbalance reserves and the storage envelope equations, could make currently reasonable accuracy thresholds unreasonable in the future.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

SDG&E appreciates CAISO’s in-depth analysis of storage performance under multi-interval optimization. The effort to identify patterns in out-of-merit (OOM) dispatch provides valuable insight into how storage resources are dispatched and whether corrective uplift mechanisms need developed and refined.

We believe this topic warrants further investigation and support a second phase of this work. While the aggregate frequency of OOM dispatch appears low, the concentration of these events during peak hours—particularly in the summer afternoons—suggests a more nuanced view is warranted.

To better evaluate the magnitude of the issue, we request CAISO separate OOM dispatch impacts by hour. This would allow stakeholders to assess whether the cost implications are material and whether it would be more impactful to prioritize other topic areas within the SDM initiative.

Finally, we encourage CAISO to consider that cost impacts may be significant in individual hours and that certain resources may be disproportionately affected due to location-specific factors and congestion. A resource-level analysis could help identify whether some assets are more vulnerable to OOM dispatch, especially from low frequency, high magnitude events

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

In general, SDG&E supports methodology enhancements to improve forecast accuracy. Including irradiance (via the saturation point and slope) in the HSL calculation could meaningfully improve data quality. However, prior to taking a position on whether iHSL is a feasible enhancement, SDG&E requests CAISO to give additional details on how this would be implemented. Would there be any changes to how this data is reported to the CAISO as compared to the current HSL reporting? Would there be an explicit formula provided for the iHSL? Would CAISO continue to validate this data for accuracy, and what checks would be conducted to ensure this value is reasonable?

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

No comment.

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

SDG&E is open to alternative guidance for reporting routine charging constraints for distribution-level storage resources other than the transmission-induced generator outage nature of work (NOW). If suitable, CAISO could create a new NOW specific to these instances, which would allow for the proper bucketing of outage information and data, or instruct the use of other NOWs such as Plant Trouble.

7. Provide your organization's comments regarding the SOC Management Topics

No comment.

8. Provide your organization's comments regarding the PRR 1627 Changes

SDG&E appreciates the data shared by CAISO regarding the PRR 1627 changes, which indicate no major impacts on battery performance from the incorporation of the flexible ramping product awards into the SOC accounting. However, given the anomalous scenario identified with negative FRU pricing, SDG&E supports the ongoing investigation of pricing impacts from implementation.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

No comment.

10. Are there alternative methods to calculate solar HSL that you recommend?

No comment.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

SDG&E has no comments on the Fluence Energy presentation at this time.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

SDG&E has no comments on the GridSME presentation at this time. 

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

No comment.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

As discussed below, the Six Cities do not oppose the CAISO’s proposed approach regarding Day-Ahead Bid Cost Recovery (“BCR”) for storage resource and do not oppose the proposal to require initial state of charge values for storage resources to be within a range of accuracy. 

The Six Cities request that the CAISO provide further clarification regarding outage reporting requirements and expectations for distribution-connected storage resources. 

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

The Six Cities reiterate their September 9, 2025 comments that, in most instances, Bid Cost Recovery (“BCR”) for storage resources is unwarranted, although the Six Cities remain open to understanding if there are circumstances where BCR may be appropriate.  At a conceptual level, these circumstances would appropriately be ones where the triggering conditions for uplift eligibility are not within the control of the market participant, such as exceptional dispatch or during market power mitigation.  As such, the Six Cities do not oppose the CAISO’s proposal to eliminate Day-Ahead BCR for Storage.  The Six Cities also do not oppose the CAISO’s proposal to require the initial state of charge value for storage resources to be within a certain range of accuracy if appropriate rules can be developed to ensure that the range is achievable for resources, including those providing regulation.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

The Six Cities do not have comments on this aspect of the Meeting at this time.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

The Six Cities do not have comments on this aspect of the Meeting at this time. 

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

The Six Cities do not have comments on this aspect of the Meeting at this time. 

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

The Six Cities understand the CAISO’s instruction that storage resources not use “transmission induced” on outage cards to describe the outage nature of work (“NOW”) when conveying availability status due to charging limitations.  However, this appears to be an area where more specific guidance from the CAISO is warranted.  If there are clarifications that the CAISO can provide regarding the appropriate NOW or other mechanism to convey availability restrictions due to charging limitations, the Six Cities request that the CAISO provide such clarifications.  If necessary, the Six Cities support updating the Outage Management Business Practice Manual to clarify the appropriate NOW for reflecting charging limitations.

7. Provide your organization's comments regarding the SOC Management Topics

The Six Cities do not have comments on this aspect of the Meeting at this time. 

8. Provide your organization's comments regarding the PRR 1627 Changes

The Six Cities do not have comments on this aspect of the Meeting at this time. 

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

The Six Cities do not have comments on this aspect of the Meeting at this time. 

10. Are there alternative methods to calculate solar HSL that you recommend?

The Six Cities do not have comments on this aspect of the Meeting at this time.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

The Six Cities do not have comments on the Fluence Energy presentation at this time. 

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

The Six Cities do not have comments on the GridSME presentation on behalf of Wellhead Power Services at this time. 

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

The Six Cities have no additional comments at this time. 

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

Southern California Edison (SCE) comments can be viewed under the subsequent questions.

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

SCE Supports Eliminating Day-Ahead BCR
SCE continues to support the Department of Market Monitoring’s (DMM) recommendation to eliminate Bid Cost Recovery (BCR) payments for storage resources in the Day-Ahead (DA) market, with limited exceptions. Specifically, SCE supports retaining BCR eligibility only in cases of exceptional dispatch, where storage resources are directed to operate in a manner that deviates from economically optimal schedules due to system needs.

CAISO’s analysis presented during the September 29 Storage Design and Modeling working group meeting confirms that the majority of DA BCR payments for storage resources are driven by bid parameter configurations that result in uneconomic schedules, rather than by system-driven reliability needs. SCE agrees that such bidding behavior should not be eligible for BCR, as they may incentivize bidding strategies that undermine market efficiency.

SCE Supports Maintaining the Current Approach for Initial State-of-Charge 
SCE supports maintaining the current default value for initial state-of-charge (SOC) per the Business Practice Manual for Market Instruments.  SCE believes the current approach is simple and intuitive.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

SCE appreciates CAISO providing analysis of the frequency of out-of-merit dispatches and the effects of binding prices on future advisory prices.  Although, out-of-merit dispatches occur infrequently and advisory pricing is usually consistent with expectations, SCE requests CAISO go further in its analysis to identify drivers of those out-of-merit dispatches.  Additional analysis may uncover unexpected market activity and outcomes that can result in further refinement.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

SCE Requests Measurable Benefits of iHSL Calculations 
CAISO has stated that implementing iHSL will improve forecasting, offering greater efficiency and accuracy. However, CAISO has not provided sufficient information for market participants to assess whether these benefits outweigh the costs and efforts required for implementation. SCE requests that CAISO quantify the expected improvements and clarify how significant these benefits will be. 

Substantial Efforts for Market Participants to Calculate iHSL 
SCE believes that iHSL is technically feasible to implement, but it will require substantial coordination and effort from market participants. The resources, time, and costs for market participants to calculate iHSL are likely much greater than those for CAISO or a trusted third party. Additionally, requiring all resources to implement the new calculation would take significant time before CAISO can obtain quality HSL data for forecasting. Generators are already providing CAISO with the necessary telemetry data to calculate iHSL. Therefore, it would be much more convenient and cost-effective for CAISO to perform these calculations.

Potential for Gaming during Supplement Events
SCE recommends that CAISO assume responsibility for calculating iHSL, rather than delegating this task to counterparties.  Currently, many contracts rely on CAISO forecasts to estimate facility output and determine payments during curtailments.  However, under the proposed approach where counterparties calculate their own iHSL values, there are concerns that counterparties may have a vested interest in overstating their actual output during curtailment events to maximize profits. This creates a risk of potential gaming, which could compromise the accuracy of forecasts and undermine the goal of improving forecasting precisions.  Unless CAISO implements robust methods to validate and ensure the accuracy of iHSL data, SCE believes it is most appropriate for CAISO to perform these calculations directly.

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

See question #4.

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

SCE Supports Not Using Transmission-Induced NOW for Distribution-Level Charging Constraints
SCE supports CAISO’s position that resources facing routine distribution-level charging constraints should not use the Transmission-Induced Nature-of-Work (NOW) code when reporting outages. These constraints are inherent to the as-available charging service and are not caused by transmission or distribution system outages. 

Outages Due to Charging Constraints Should Not Be RAAIM-Exempt
SCE strongly believes that resources electing as-available charging service should not be exempt from Resource Adequacy Availability Incentive Mechanism (RAAIM) penalties. These resources were aware of the potential risks and limitations at the time of contracting and should be held accountable for their RA obligations.

Additional Clarity Is Needed for NOW to Use for Charging Constraints
To ensure consistent and transparent reporting across all market participants, SCE requests CAISO to provide clear guidance on which specific nature-of-work code should be used to report charging constraints. This will help avoid confusion and ensure that resources are not inadvertently exempt from RAAIM penalties. 

SCE recommends CAISO explore whether creating a new nature-of-work code specifically for distribution-level charging constraints would be appropriate. This would allow resources to accurately report their limitations, and RAAIM penalties could be appropriately assessed based on this code, ensuring fair treatment and accountability. 

Request to Formalize Future Changes and Clarifications in the BPM
Finally, SCE encourages CAISO to document these requirements in the BPM and communicate any changes to stakeholders.

7. Provide your organization's comments regarding the SOC Management Topics

There appears to be an error in the same formula shown on pages 46 and 47 of the Storage and Design and Modeling presentation dated September 29, 2025.  The sign in front of the charging energy term which contributes to SOC should be consistent with the convention use for the IFM and RUC equations.  SCE requests CAISO to confirm the accuracy of the formula and make corrections as appropriate.  

8. Provide your organization's comments regarding the PRR 1627 Changes

SCE does not have any comments.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

See question #4.

10. Are there alternative methods to calculate solar HSL that you recommend?

See question #4.

11. Provide your organization's comments on the presentation offered by the Fluence Energy

SCE does not have any comments.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

SCE does not have any comments.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

SCE does not have any comments.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

7. Provide your organization's comments regarding the SOC Management Topics

8. Provide your organization's comments regarding the PRR 1627 Changes

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

10. Are there alternative methods to calculate solar HSL that you recommend?

11. Provide your organization's comments on the presentation offered by the Fluence Energy

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

Vistra respectfully requests the CAISO read and internalize our comments. We hope to see engagement in trying to understand viewpoints and efforts to try to seek common ground going forward. 

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

The need for Bid Cost Recovery (“BCR”) whether Day-Ahead or Real-Time is largely driven by CAISO overly constraining and mitigating storage resources such that the Scheduling Coordinator (“SC”) finds it more difficult to manage their use limitations and associated opportunity costs and risks. As previously stated in our comments on the June workshop, Vistra is willing to negotiate a mutually agreeable outcome that meets CAISO’s and storage operators’ interests. CAISO appears to not want to provide uplift to storage, and Vistra as a storage operator desires the ability and tools to effectively manage our use limitation through our bids without market intervention such as mitigation or State of Charge (SOC) constraints that limits our ability to manage the asset effectively.

CAISO Should Allow Storage Operators to Manage its SOC

As previously noted, CAISO should cease its practice of overly constraining storage assets through applying Market Power Mitigation (“MPM”) that results in mitigated prices that do not reflect the asset’s opportunity costs, enforcing the Ancillary Service (“AS”) State of Charge (“SOC”) constraint that when it binds issues energy schedules, and converting an AS obligation into an energy position when derates occur. If CAISO ceases taking these market interventions that lead to uneconomic dispatches, Vistra will support eliminating Bid Cost Recovery (“BCR”). If these changes are made in one market, then Vistra can only support eliminating BCR in the market where the market rule changes are made.

Vistra continues to request the CAISO seriously weigh our proposal to:

• Exempt Limited Energy Storage Resources (“LESR”) and Hybrid Resources from MPM,
• Remove the AS SOC constraint and explore deactivating the envelope equations, and
• Cease converting AS awards into energy awards when a LESR experiences an outage where the penalty prices associated with the Upper Economic Limit or Lower Economic Limits trigger energy awards.

The last two bullets should be acceptable from a market design perspective with accompanying changes that:

• Identify the Unavailable Quantity due to outage or SOC availability as No Pay Unavailable Quantities,
• Identify incremental RT AS if Unavailable Quantity are identified in RTM, and
• Categorize it as AS No Pay Unavailable Capacity subject to rescission.
• Allow CAISO to eliminate uplift fully mitigating their uplift concerns.

To be clear, if CAISO does not make these needed market changes then a robust uplift framework and a reasonably accurate Default Energy Bid (“DEB”) are needed. CAISO’s current command-and-control approach overly constrains storage and its opportunity costs.

Initial SOC Is Not BCR Issue but a Serious Market Gap

Vistra has previously proposed the CAISO model a State of Charge constraint, ideally a biddable SOC product, that would identify the difference in SOC modeled in IFM and the telemetered SOC in any given hour of the market to identify incremental SOC need for that hour. This includes the concerns surrounding the delta between the modeled IFM SOC for the initial hour due to bid-in initial SOC and the telemetered SOC in the initial hour. With a robust market design solutions the CAISO should:

• Identify the resources that are outside a deadband of their bid-in SOC to include in a SOC product no-pay calculation.
• Issue SOC awards to resources eligible to receive the SOC award to bring the system back to its IFM modeled SOC levels in that hour.

In the case that CAISO does not compromise with stakeholders on the extent it chooses to take storage management into its own control and therefore BCR cannot be eliminated, we do not support eliminating BCR for this as the lack of a SOC product that identifies unavailable SOC bid-in in the initial hour and then procures incremental SOC need in Real-Time is a market gap not a bid cost recovery issue.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

Vistra appreciates the CAISO providing analysis on MIO. While MIO may be leading to suboptimal storage operations in select instances there are also instances that the Opportunity Cost in a future advisory interval do impact the binding prices. As stated in our comments on the June 30th workshop, the CAISO showed how the opportunity cost of holding the SOC for a future interval tightness set the price in the binding interval in a recent Market Performance & Planning Forum.[1] We requested the CAISO under this effort perform more education including:

• Multi-Interval Optimization education,
• Frequency and magnitude that the opportunity cost of holding, charging, or discharging storage sets the binding interval clearing price versus the opportunity cost does not set the binding clearing price, and
• Magnitude of differences in the schedules and clearing prices for a given interval across all advisory and binding intervals for better understanding of the skew of pricing observed by participants versus observed in earlier advisory runs.

While the data provided is positive step, it does not yet help to either prove the hypothesis true or false as to whether future intervals are often impacting binding intervals enough such that MIO should be deprioritized. Until we collectively understand whether the argument that future intervals are impacting binding awards where the pricing does not materialize, we believe more granular price impact data needs to be investigated and provided.

[1] Market Performance and Planning Forum, June 26, 2025, page 83-84, https://www.caiso.com/documents/presentation-market-performance-and-planning-forum-jun-26-2025.pdf.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

No comments. 

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

No comments. 

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

Vistra requested the scope of this effort include adding storage specific outage types to the appropriate outage card Nature of Work. This is an approach that clarifies in which NOW a storage-specific cause should be reported. An approach that only details which NOW not to use falls short of our ask. See below the slide presented in the scoping meetings requesting that the Outage Management Business Practice Manual be updated to include the outage types we are identifying in this working group in the NOW definitions.

While Vistra did not include the distribution charging constraints in our initial list of outages needing clarification, in conversations with CAISO regarding updating NOW definitions during 2025 distribution triggered outages have been discussed. As a next step, Vistra suggests systematically walking through the outage scenarios discussed in the Proposed Revision Request process in addition to the outages above to ensure a comprehensive list and to seek alignment on the NOW that best fits the cause. The output of this review should then be taken through the PRR process to update the Business Practice Manuals.

Any cause that is outside the control of the Generator Owner for outages identified as forced should be associated with a Nature of Work that is exempt from the Resource Adequacy Availability Incentive Mechanism consistent with CAISO Tariff.

7. Provide your organization's comments regarding the SOC Management Topics

It is paramount that CAISO rules and practices shift responsibility for SOC management from the ISO to SC. The CAISO should subject the SC to any applicable penalties and it would be appropriate not to provide uplift if the CAISO shifts the responsibility for managing the assets more fully onto the SC.

The recent years of operational experience have shown us that market interventions through constraints or inaccurate mitigation are the main drivers of uneconomic market outcomes that we feel are unacceptable. While Vistra appreciates more transparency efforts on the envelope equations, Vistra does not support the implementation of the envelope constraints as it adds another market intervention CAISO is taking to take SOC management from SCs and to drive ISO-driven market outcomes.

As mentioned in our earlier comments this year, uneconomic market results that are the result of CAISO interventions are due to command-and-control design decisions made by the CAISO. It is prudent to shift the responsibility for SOC management to the SC and subject the SC to penalties for failure to deliver on its obligations.

This direction is more compliant with FERC Order 841 direction where FERC decided:

“Consistent with the NOPR, we find that each RTO/ISO must permit electric storage resources to manage their state of charge because it allows these resources to optimize their operations to provide all of the wholesale services that they are technically capable of providing, similar to the operational flexibility that traditional generation resources have to manage the wholesale services that they offer… We therefore agree with commenters that resources using the participation model for electric storage resources must have the ability to self-manage their state of charge and it is often desirable to allow them to do so. Providing this flexibility will allow resource owners/operators to ensure their own Minimum and Maximum States of Charge are not violated… Therefore, we require each RTO/ISO to allow resources using the participation model for electric storage resources to self-manage their state of charge. We also find here that a resource using the participation model for electric storage resources that self-manages its state of charge will be subject to any applicable penalties for deviating from a dispatch schedule to the extent that the resource deviates from the dispatch schedule in managing its state of charge.”[1]

Under the FERC Order 841 process it was identified that Storage operators should manage the SOC of storage however the CAISO’s existing approach takes this control from storage operators. If CAISO wants to control the assets, which increases risks of uneconomic market outcomes, it is necessary for CAISO to provide robust uplift to storage. This requires CAISO to decide whether it wants command-and-control or if it wants to limit uplift.

CAISO can choose to allow storage operators to have more control over our asset management as requested here. In that case, it becomes the storage operators’ actions without CAISO intervention that lead to market outcomes hence it is acceptable for us not to receive uplift. The uplift debate is a red herring distracting from the more important policy issue that CAISO’s design has significant market interventions to take the SOC management of the resources’ away from storage operators, which leads to ISO-driven dispatches that may be uneconomic.

As a storage operator, we want to see the market interventions leading to sub-optimal market actions be eliminated. As a next step, Vistra requests the CAISO engage meaningfully in a negotiation around what it may be willing to change to remove market interventions in exchange for storage SC being willing to agree that by transferring SOC management to SCs that market results become SC-driven and are not eligible for uplift.

Additionally, Vistra supports CESA’s calls for documentation of the suite of storage modeling constraints. This will be helpful to make sure the CAISO understands which constraints we are asking them to deactivate. Vistra is not asking CAISO to cease to use the SOC constraints used to identify feasible market awards as these are critical to the market. However, we are seeking the deactivation of the AS SOC constraints and envelope equations. As previously stated, replacing these constraints with identifying unavailable amounts to assess no-pay and to procure incremental services to replace those unavailable must be pursued to balance their elimination.

[1] FERC Order 841 Paragraphs 246-248.

8. Provide your organization's comments regarding the PRR 1627 Changes

Vistra appreciates the update on how adding Flexible Ramping Up product to the SOC terms that ensure the amount of energy and AS are feasibly awarded. It does not make sense to the Vistra team that there would be negative FRU pricing. We assume the CAISO team is evaluating the market results and exploring changes to help resolve what appears to be a market defect. Please provide transparency on those discussions or at a minimum the commitment to expeditiously address.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

No comments. 

10. Are there alternative methods to calculate solar HSL that you recommend?

No comments. 

11. Provide your organization's comments on the presentation offered by the Fluence Energy

Vistra has other channels for exploring vendors that we believe are best suited for our projects, and those avenues are managed by business representatives not regulatory representatives. It was unclear if Fluence was implying CAISO should be a client. If CAISO feels it is the prospective client being pitched to then Vistra suggests that it explores improvements with vendors in a different process than a policy initiative.

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

The presentation highlighted Vistra’s concerns that the CAISO’s processes to establish reasonably appropriate mitigated prices is struggling. As we mentioned previously, CAISO is struggling to define mitigated prices that allow storage assets to manage their use limitations. This challenge is compounded for assets with multiple components with both storage and non-storage elements as the presentation highlighted. We reiterate that CAISO should concede some control to storage, co-located, and hybrid by acknowledging its challenges in determining a reasonable estimate for their costs and opportunity costs and deactivating mitigation. As that will transfer control to SCs, we understand that it would be principled and reasonable to then make the assets ineligible for uplift.

If CAISO decides not to entertain this novel idea which could meet all parties’ needs then in addition to making its uplift framework more comprehensive it will also need to establish more accurate Default Energy Bids for all types of storage from stand-alone to co-located and hybrids.

In the past, Vistra has requested CAISO enhance the DEB framework such that:

• Storage must be able to charge where it would be overly punitive to mitigate charging bids down as no other demand bids are mitigated down in CAISO’s market – no charging bid mitigation.
• Storage must be able to have reasonable assurance that they can reflect discharge bids even when mitigated that allows the storage to preserve SOC needed to meet a reasonable amount of their schedules later in the day
• Storage must have ability to reflect charge spread between its discharge and charge mitigated bids that is at least components for its registered VOM where the value of moving from charge into discharge should be at least registered VOM.
• Storage not allowed to submit reference level change requests and should be allowed to fully comply with FERC Order 831.

During the scoping meeting Vistra recommended that a better Storage DEB may be able to be established by aligning it with an opportunity cost methodology like hydro DEB (with storage). Vistra is willing to present on what this methodology could be. 

The alternative is our proposal to deactivate mitigation and AS SOC or envelope constraints in exchange for foregoing uplift and being exposed to no-pay rules.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.

None.

1. Please provide a summary of your organization's general comments on and materials shared on Sep 29th meeting

WPTF appreciates the opportunity to provide feedback on the ongoing policy discussions affecting storage resources in CAISO markets. Our comments reflect a consistent theme: the need for equitable treatment of storage resources and thorough understanding and vetting of all potential changes. We encourage CAISO to take a holistic, transparent, and data-driven approach that acknowledges the operational realities of storage, ensures fairness across all resource types, and supports continued market participation and reliability. We look forward to continued engagement on these important issues.

Our comments below reflect the following:

• Should not eliminate Day-ahead Bid Cost Recovery (DA BCR) absent a more holistic approach that aligns with the intent of a make whole payment structure
• Encourage the CAISO to provide guidance as to how storage resources should be reflecting charging restrictions in outage cards, not just informing participants what Nature of Work (NOW) not to use
• Encourage continued discussions around the planned envelope constraints such that participants have a better understanding of how it will impact resource schedules across the day
• Look forward to continued analysis on Multi-interval Optimization (MIO) at a resource level granularity as well as discussions around how to address negative Flexible Ramping Up (FRU) prices

2. Provide your organization’s comments regarding the Day-Ahead BCR for Storage

Make-whole payments ensure that resources operating in the market at least recover their costs, as reflected in their market offers (i.e., bids). It is essential that this feature is applied fairly and equitably across all resource types. CAISO should not eliminate the Day-Ahead BCR (Bid Cost Recovery) for storage without first establishing a comprehensive alternative that considers both the Day-Ahead (DA) and Real-Time (RT) markets.

We support revisiting the make-whole payment structure for storage resources, recognizing that the current framework was originally designed for traditional generators. However, we are concerned with the current messaging that suggests simply eliminating DA BCR for storage. Doing so, while only modifying Real-Time BCR, would introduce a discriminatory outcome, where all other resource types can receive make-whole payments in both markets, while storage is limited to RT only.

For example, consider a storage resource that receives a Day-Ahead schedule to charge during midday and discharge during peak hours. When reviewing its costs and revenues across the day, the resource operates at a loss and should be eligible for DA BCR. This situation can and does occur, particularly in a complex market with binary variables, where LMPs may fall slightly below the resource’s accepted energy offer. In Real-Time, the resource bids based on real-time conditions and ends up with the same schedule as its Day-Ahead schedule. Under the current framework, it would receive DA BCR (and no Real-Time BCR) because its real-time schedules align with day-ahead schedules. This is appropriate because the resource will be paid entirely based on day-ahead prices and thus will not receive sufficient revenues to cover costs.

However, under a framework that eliminates DA BCR it is our understanding that this resource would receive no make-whole payment, even if its total market revenue falls short of covering its costs. That would be an unacceptable outcome. Or if the proposal would be to consider its real-time offers relative to its real-time prices to determine if a real-time make whole payment is necessary, that too would be inappropriate because from a settlements perspective it receives revenues based on day-ahead prices not real-time.

We recommend continued discussions around a more holistic approach that evaluates a resource’s total operating costs and market revenues without disregarding the Day-Ahead market altogether.

3. Provide your organization's comments regarding the Performance of CAISO Storage Resources Under Multi-Interval Optimization

We appreciate the analysis provided. However, to fully assess the impact of Multi-Interval Optimization (MIO) on storage resources, more granular data is needed, particularly nodal prices specific to storage resources, rather than just the System Marginal Energy Cost (SMEC).

We also appreciate CAISO’s acknowledgment during the stakeholder meeting that a more detailed analysis is forthcoming. We look forward to reviewing that analysis and engaging in further discussion.

4. Is irradiance-based high sustainable limit (iHSL) implementable? What challenges do you foresee?

5. What advantages or disadvantages do you see if the irradiance-based high sustainable limit (iHSL) formulation were a requirement for solar resources?

6. Provide your organization's comments regarding the Outage Reporting for Distribution-Level Charging Constraints

We appreciate CAISO’s guidance on which Nature of Work (NOW) outage cards not to use when reporting distribution-level charging constraints. However, it is equally important for CAISO to clarify which specific outage cards should be used in these situations.

Scheduling Coordinators (SCs) need clear instructions on how to accurately reflect these restrictions through the outage card process. We respectfully request that CAISO provide this guidance so that SCs can appropriately report such outages moving forward. Furthermore, we ask that this conversation take place in a public stakeholder meeting that provides an opportunity for stakeholders to provide feedback for consideration.

7. Provide your organization's comments regarding the SOC Management Topics

WPTF appreciates the ongoing discussion around the current and planned SOC (State of Charge) formulations and constraints. We understand that with the implementation of Day-ahead Market Enhancements (DAME), CAISO plans to use envelope equations to manage SOC in the Day-Ahead market, while retaining the existing SOC constraints in the Real-Time market. This would result in different SOC management methods between the two markets, a change that introduces added complexity for storage resources.

WPTF would like to take this opportunity to remind the CAISO that during the final policy proposal on DAME, it committed to "continue evaluating the efficacy of the envelope equations, their impact on existing constraints, best methodologies for setting multipliers, and what the initial multipliers will be." We appreciate the CAISO using this policy effort to continue discussing the envelope equations however we ask that there be additional discussion with examples that highlight how storage resources will be managed across the day and that the discussions are not simply limited to a review of the implementation equations alone.

WPTF has also raised questions previously about the impact of the envelope equations when a resource reaches its upper or lower SOC limit. Therefore, we again ask that the CAISO provide examples of how the new envelope equations will work under various scenarios, one of which includes a resource reaching the upper or lower limits midday.

Discussing these implications now is essential to ensure market participants understand the operational challenges and also can take them into account during the ongoing discussions around make-whole payment frameworks.

8. Provide your organization's comments regarding the PRR 1627 Changes

Negative Flexible Ramping Up (FRU) prices are concerning, especially if resources are now expected to pay to provide a service. This outcome appears to be inconsistent with the original intent of the Flexible Ramping Product (FRP), which was never designed to impose costs on resources for being awarded the product. This is especially important to address given it is not a biddable product and resources have no ability to indicate to the market if its willing to provide at a cost.

We strongly encourage CAISO to initiate discussions with stakeholders as soon as possible to identify potential solutions and address this unexpected pricing result.

9. How much effort is required to configure or reconfigure HSL for a new vs existing resource?

10. Are there alternative methods to calculate solar HSL that you recommend?

11. Provide your organization's comments on the presentation offered by the Fluence Energy

12. Provide your organization's comments on the presentation offered by the GridSME on behalf of Wellhead Power Services

We support ensuring that all resource types in the market have accurate Default Energy Bids (DEBs). As CAISO begins discussions around hybrid DEBs, we believe these conversations should encompass all types of hybrid configurations, including solar-plus-storage, wind-plus-storage, thermal-plus-storage, and other combinations. We do see the concern raised by Wellhead with regards to the inability for gas plus storage to be modeled as a hybrid absent consideration of a more appropriate DEB.

Furthermore, we would like to take this opportunity to remind the CAISO that it has made a commitment to address known flaws in DEBs. This commitment further supports discussions around an appropriate gas plus storage DEB but we also respectfully request that the CAISO take up discussions around other known flaws with existing DEB structures.

13. Please provide any additional comments, feedback, or examples in the Sep 29th stakeholder meeting. You may upload examples or data using the “Attachments” field below.