Comments on 4/27 Intertie Schedule Modeling Workshop

1. Please provide your organization's overall feedback regarding the Intertie Schedule Modeling Evolution on CAISO Interties presentation held on April 27, 2026.

SCE believes that the discussions will be complicated and that the issues will need to be considered in a wholistic manner rather than independently. SCE also believes that before starting the discussions CAISO needs to both address questions concerning the current transitional method for intertie scheduling and provide data and analysis on how the DGAPs will be calculated.

2. Please provide feedback regarding the topics and issues to evaluate (slide 17), including identification of additional or different topic areas.

The listed issues seem like a good start, but SCE emphasizes that most of the issues cannot be treated independently. For example, the very important questions of whether there should be one single price at each Tie, as is currently the case under the SP-Tie model, or potentially multiple prices under a GAP-Tie model has implications for both CRR modeling and RA MIC allocations. This is especially clear at a Tie point like Malin which is an internal EDAM intertie, but also an external CAISO intertie. Ensuring that both internal EDAM resources and external EDAM resources are treated similarly, and that current commercial structures are accommodated, or at least allowed to adapt, will not be easily done. Further, resources located outside of EDAM should not face different situations depending on whether they deliver their power to the CAISO through other EDAM BAAs or outside of EDAM to a CAISO intertie.

As SCE has requested in past comments, before these discussions can proceed two things need to happen:

• CAISO needs to fully explain how the existing interim system functions. SCE repeats several requests pertaining to the functioning of the current mechanism in question 3.
• The CAISO needs to provide data and analysis on how the DGAPs will be calculated and how big an issue potential different prices at the same intertie is expected to be.

3. Please provide any feedback, including identification of issues to address, regarding the discussion and processes on RA imports into the CAISO balancing area modeled under a GPA-Tie modeling design.

Before any discussion of how RA imports under a GAP-Tie model will function, SCE has outstanding questions and comments about how the current transitional process for non-resource specific (NRS) RA Import re-assignment will work:

• SCE would like to kindly re-request that CAISO provide a bid-to-bill example of the re-assignment process, so stakeholders can get a better idea of how to operationalize the process and also discuss differences in CAISO settlements from pre-EDAM importing to post-EDAM re-assignments
• CAISO Tariff and BRS language suggests that re-assigned generators just generally need to bring their energy to the CAISO BA, and not specifically to the initial CAISO intertie/DGAP that the original NRS RA Import may be shown at. Can CAISO clarify if the obligation for re-assigned generator should be that they would need to deliver/tag their energy to the original intertie? If not, does this create potential misalignment between MIC/IARs and actual energy deliveries for RA imports to the CAISO BA?
• Stakeholders should discuss how CARB GHG compliance obligations may be assessed for reassigned generators
• It was suggested at the workshop that the ‘GGAP concept’ was ‘not useful’ and that at slide 35 the process was ‘simplified’ from previous. Can CAISO please detail what has actually changed here and how it is ‘simplified’ from the past workshop example?

4. Please provide any additional feedback not already captured on the presentation and the overall initiative.

No additional feedback.

1. Please provide your organization's overall feedback regarding the Intertie Schedule Modeling Evolution on CAISO Interties presentation held on April 27, 2026.

As always, The Energy Authority (TEA) appreciates the staff time and effort that went into the presentation. The detailed scheduling examples were very helpful for understanding the intertie scheduling model CAISO envisions.

TEA, however, does not find that model to be compatible with the forward firm capacity and energy contracting norms in the Western Interconnect and continues to have deep concerns that CAISO’s proposed changes will significantly and irreparably harm well-functioning markets that are used by Load Serving Entities to financially hedge positions, meet RA and RSE compliance obligations, and value transmission and generation resource investments. It appears there is a strong disconnect in understanding and positions between CAISO staff and market participants in this area, which needs to be at least somewhat resolved before moving forward.

TEA also is not convinced by CAISO’s assertion that Day-Ahead to Real-Time model accuracy would be meaningfully improved across all or even most scenarios by moving to a GAP-Tie model and does not believe that CAISO has adequately explained the benefits it expects market participants would receive if modeling accuracy was able to be meaningfully approved.

Further, TEA continues to take issue with CAISO’s description of the GAP-Tie model being the model that is used for WEIM, and CAISO's assertion that it therefore is appropriate for Western day-ahead markets. The GAP-Tie model is used in WEIM in the context of imbalance energy dispatch and ETSR accounting, not for pricing or clearing intertie transactions. Instead, the overwhelming majority of transactions and volumes flowed from source to sink across WEIM BAAs, including imports and exports at CAISO's interties, are hourly-block energy schedules that are not valued or dispatched using a GAP-Tie model.

Overall, TEA believes this initiative is missed an opportunity to identify a clear problem statement and instead jumped straight to a solution set that many find extremely problematic and at odds with their contracting needs and expectations. TEA would like to see CAISO take a step back, focus on identifying a set of concerns or issues held by CAISO and stakeholders, and then move on to establishing common principles with stakeholders for assessing potential solutions – as well as guardrails for acceptable trade-offs. Taking an extra month or two to do this is well worth the time and effort given the importance of intertie market policy to multiple CAISO markets and processes. 

2. Please provide feedback regarding the topics and issues to evaluate (slide 17), including identification of additional or different topic areas.

No additional comments at this time.

3. Please provide any feedback, including identification of issues to address, regarding the discussion and processes on RA imports into the CAISO balancing area modeled under a GPA-Tie modeling design.

No additional comments at this time.

4. Please provide any additional feedback not already captured on the presentation and the overall initiative.

No additional comments at this time.

1. Please provide your organization's overall feedback regarding the Intertie Schedule Modeling Evolution on CAISO Interties presentation held on April 27, 2026.

TransAlta Energy Marketing U.S. (TEMUS) appreciates the additional detail on intertie schedule modeling provided during the April 27 workshop and the opportunity to provide comments.

Intertie scheduling in EDAM is a much bigger change than stakeholders had anticipated when the tariff was originally filed, and TEMUS supports the CAISO’s decision to make intertie scheduling as a separate initiative.

TEMUS agrees with other stakeholders that the CAISO should take a holistic approach to intertie scheduling and consider impacts on other market design elements in both the Extended Day-ahead Market (EDAM) and the CAISO, including Congestion Revenue Rights (CRRs) within CAISO and bidding and pricing at internal and external EDAM interties.

2. Please provide feedback regarding the topics and issues to evaluate (slide 17), including identification of additional or different topic areas.

Regarding single vs. multiple prices at internal EDAM interties, TEMUS requests more information about how the CAISO would determine which prices would apply, and the impact on settlement prices. In general, there appears to be a gap between stakeholders’ understanding how a design element would function and how that element would apply on settlement invoices for Market Participants. First principles suggest that a single price, in addition to consistent, predictable price formation, would improve market efficiency by increasing price transparency: there is a leap that still needs more explanation between increasing physical efficiency through better computer modeling and increasing market efficiency.

In addition, TEMUS would appreciate additional detail regarding the impact of shift factors and Generation Distribution Factors on Scheduling Point (SP) versus Generation Aggregation Point (GAP) pricing.

3. Please provide any feedback, including identification of issues to address, regarding the discussion and processes on RA imports into the CAISO balancing area modeled under a GPA-Tie modeling design.

Under the (current) transition period, intertie bidding at internal EDAM interties will be restricted to Resource Adequacy (RA) imports.

Multiple stakeholders, including the Department of Market Monitoring (DMM) and the Market Surveillance Committee (MSC), have raised concerns regarding the incentive to self-schedule within the EDAM footprint. The most immediate solution would be to expand bidding at all interties for all Market Participants. This equitable treatment of transfers would disincentivize self-schedules, increase market efficiency, and have positive impact on powerflow modeling.

Instead, the CAISO’s goal is to eliminate intertie scheduling all together at internal EDAM interties, thereby increasing the incentive to self-schedule.

TEMUS looks forward to detailed discussions regarding transacting at internal and external EDAM footprint interties in future workshops.

4. Please provide any additional feedback not already captured on the presentation and the overall initiative.

The CAISO appears to be committed to ending the transition period in 2027, when intertie scheduling at internal interties will no longer be allowed for any transfers. TEMUS urges the CAISO to consider extending the transition period if stakeholder discussion continue to evolve. As the EDAM implementation has demonstrated, it would be prudent to continue to work with stakeholders towards a complete solution than to rush towards an arbitrary deadline only to uncover implementation issues later.