Comments on 3/18 Meeting

1. Please provide your organization's overall feedback regarding the Intertie Schedule Modeling Evolution on CAISO Interties presentation held on March 18, 2026.

Comments on the Intertie Schedule Modeling Evolution Stakeholder Workshop

March 18, 2026

Department of Market Monitoring

April 1, 2026

Summary

DMM appreciates the opportunity to comment on the March 18, 2026 Intertie Schedule Modeling Evolution Stakeholder Workshop.[1] DMM supports the ISO’s efforts to improve congestion modeling for intertie schedules by replacing scheduling points with generation aggregation points (GAPs). However, DMM does not support an approach that would result in multiple prices for the same intertie. DMM believes the ISO should associate a single GAP per intertie for modeling and pricing of all transactions at an intertie. Whether or not importers and exporters can economically bid at “internal EDAM interties” with the CAISO balancing area is an important issue that needs to be discussed in the upcoming workshops.

Comments

GAP-Tie modeling can improve congestion management compared to SP-Tie Modeling

CAISO intertie schedules are currently modeled as injected/withdrawn at scheduling point (SP) nodes associated with a specific intertie. The location of the actual generation or load associated with the intertie schedules is not known, but the associated generation or load is very clearly not at the scheduling point. Therefore, the current modeling of intertie schedules as if they were injected/withdrawn at the scheduling point can create inaccurate estimates of physical power flows and losses over the transmission system. As explained by the ISO, this known inaccuracy affects congestion management, pricing, and settlements.[2]

The ISO aims to improve power flow modeling by changing the modeling of intertie schedules from being treated as injections/withdrawals at a scheduling point to being injections/withdrawals at generation aggregation points (GAPs). This approach, which the ISO refers to as GAP-Tie modeling, can improve congestion modeling, management, and pricing. However, for reasons explained in these comments, DMM believes this GAP-Tie design should be implemented in a way that ensures a single price is maintained for a given intertie.

The ISO should aim to improve congestion modeling while maintaining a single price per intertie  

Moving to GAP-Tie modeling from the current approach of modeling schedules as simple injections at tie points may improve congestion modeling, management, and pricing. However, the GAP used in this new approach is still not the actual location where power associated with an import is injected. It is not clear how much additional value there is from modeling multiple GAPs per tie relative to a single GAP. Further, DMM believes, in terms of market design, it is much better to have a single price per intertie, and that all imports and exports at that intertie settle on that price.

Multiple GAPs per intertie would create multiple prices which can create a variety of market design issues. For example, multiple prices for the same intertie could result in imports clearing at higher offer prices over other imports with lower offer prices—solely because of the differences in the congestion and loss price components between their GAPs. This might make sense if the congestion cost differences between the competing import offers were accurately represented by the GAP congestion prices. But the GAP is still not the actual congestion impact of the imports. The imports are not from generation physically at the GAP. The ISO would not know the real relative congestion price differences, and it is not clear whether choosing one import offer over another based on the difference in congestion prices between GAPs is a sensible policy that supports efficient market outcomes.[3]

Economic bidding at the internal EDAM interties with CAISO

During the transitional intertie modeling period, the ISO will only support economic bidding for a limited set of schedules at internal EDAM interties with CAISO.[4] It appears that the ISO planned, at least prior to the current stakeholder process, to not support economic bidding at internal EDAM interties after the transitional period. This will limit the ability of entities to participate in ISO markets.

DMM notes that the EDAM design maintains the transmission scheduling rights systems of the non-CAISO balancing areas joining EDAM. A balancing area joining EDAM is not the same as joining the ISO footprint as a participating transmission owner. That is, an internal EDAM intertie between a non-CAISO BAA and the CAISO BAA is not the same as connections between participating transmission owner systems within the CAISO BAA.

EDAM schedules need to have accompanying transmission scheduling rights. If those transmission rights are not used by EDAM/WEIM energy schedules, then presumably those rights become available for others to use. Therefore, if bidding were allowed at internal interties, an importer who could bring power to the intertie for a lower cost than the EDAM transfer could clear the EDAM market and would then be able to schedule the power in real-time using available transmission. Without bidding allowed, the importer could not compete with the EDAM transfers.

The relevance of this example may depend on the EDAM BAA that the importer schedules rights across not supporting intertie bidding. If this EDAM BAA allows intertie bidding at its interties, the importer could bid at the intertie needed to cross the BAA, and the market could optimize whether that supports a transfer or meets the load in the EDAM BAA.

The ISO should carefully reconsider whether not supporting economic bidding at internal EDAM interties with CAISO is an appropriate policy.

[1]  Intertie Schedule Modeling Evolution on CAISO Balancing Area Interties - Stakeholder Workshop, March 18, 2026: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Intertie-Schedule-Modeling-Evolution-on-CAISO-Balancing-Area-Interties-Mar-18-2026.pdf

[2]  Extended Day-Ahead Market Intertie Scheduling, EDAM Intertie Scheduling Team, November 4, 2025, p iii:  https://stakeholdercenter.caiso.com/InitiativeDocuments/Intertie-Scheduling-Scenarios-Extended-Day-Ahead-Market-Nov-4-2025.pdf

[3]  Additional potential issues are listed in DMM Comments on the Intertie Scheduling EDAM Implementation Workshop November 5-6, 2025, November 10, 2025: https://www.caiso.com/documents/dmm-comments-on-the-intertie-scheduling-edam-implementation-nov-05-06-2025-workshop-nov-11-2025.pdf

[4]  Transactions will be limited to resource adequacy and Renewable Portfolio Standard contracts with an unknown source or that are outside the EDAM footprint.

2. Please provide your suggestions regarding areas of focus, issues and policy topics to discuss at upcoming workshops arising as a result of intertie schedule modeling design considerations.

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

3. Please provide any additional feedback not already captured.

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

1. Please provide your organization's overall feedback regarding the Intertie Schedule Modeling Evolution on CAISO Interties presentation held on March 18, 2026.

SCE appreciates the time that the CAISO has taken in creating and presenting the examples provided. SCE believes that they have contributed to stakeholders’ understanding of the complex issues involved. However, the job of making sure that stakeholders understand the new mechanism and implications for commercial transactions is far from being done. The examples were complicated and SCE believes that stakeholders would benefit from another session going through the examples again, with additional details included such as discussed in the answer to question 2 below. This would give stakeholders time to review the examples and develop questions. For example, SCE understands how the more accurate modeling of the energy leads to increased accuracy in congestion management, but has questions about just how big the changes in schedules, prices and congestion will be, and how often they may show up. SCE also has questions about how the examples were constructed and where the hypothetical numbers in them came from (see the specific questions and requests in the answer to question 2 below).

SCE also requests that the CAISO provide analysis on the relative levels of SP-Tie prices and GAP-Tie prices to help stakeholders understand how big the changes could be, and how big potential changes in Tie prices between the different DLAPs could be. This analysis should also help stakeholders understand the expected level of efficiency gains so they can be compared to potential costs from commercial changes.

2. Please provide your suggestions regarding areas of focus, issues and policy topics to discuss at upcoming workshops arising as a result of intertie schedule modeling design considerations.

SCE suggests that the next area of focus should be on how the GP-Tie structure will interact with current commercial transactions on the interties, such as CRRs and the MIC process for RA resources. It appears that under GAP-Tie the CRRs will need to be specific to the GAP-Tie. Further, it seems like because of better congestion management slightly more CRRs may be available under this model, but at a loss of more generic usefulness. Stakeholders need to clearly understand these potential implications to weigh off the potential commercial costs against the improved efficiency. Currently, CRRs source/sink at an SP-TIE, which can be used for power flowing into or out of several different BAAs that connect at the single SP-Tie.

SCE also has the following requests for clarification and additional information on EDAM Intertie Modeling and Pricing Formulation:

Request for Clarification and Additional Information

To facilitate effective participation among market stakeholders and enhance transparency in EDAM intertie modeling and pricing formulation, we respectfully submit the following requests for clarification and supplemental information.

Calculation of DGAP Shift Factor

• We respectfully request clarification concerning the methodology used to calculate the DGAP shift factor.
• Specifically, is the DGAP shift factor determined as a weighted average of individual generator shift factors, utilizing Generation Distribution Factors (GDFs) as weights?
• Should this not be the case, we kindly request a detailed description of the alternative formulation employed.

Power Flow Formulation within Network Analysis

We request clarification regarding the approach taken in Network Analysis (NA) for power flow formulation and resolution. In particular, we seek information on the following points:

• Is a unified WECC-wide (or EDAM-wide) network model employed for solving power flow?
• If so, how is this reconciled with Security-Constrained Unit Commitment (SCUC) power balance equality constraints, which are enforced at the Balancing Authority Area (BAA) level, especially in the context of calculating Marginal Energy Cost (MEC) and Marginal Cost of Losses (MCL)?

• Alternatively, is power flow addressed at the EDAM BAA level, treating each BAA as an electrical island running its own power flow?

• How are non-EDAM BAAs represented within the power flow analysis? Are non-EDAM BAAs modeled solely with network topology, or do they include both network topology and power injection/withdrawal?

Examples of SP ITC/ISL and DGAP Constraint Binding

We respectfully request illustrative examples to demonstrate the proper formulation, interpretation, and interaction of Scheduling Point (SP) Marginal Cost of Congestion (MCC) and DGAP MCC in the following conditions:

• When SP ITC/ISL import/export constraints are binding
• When DGAP import/export constraints are binding

Multiple-Intertie and Multiple-DGAP Pricing Scenarios

We request examples that illustrate dispatch and price formulation in these scenarios:

• A single DGAP applied to multiple interties
• A single intertie associated with multiple DGAPs

These examples would be invaluable in clarifying how dispatch decisions and pricing components are determined within complex intertie configurations.

Publication of Generation Distribution Factors

We respectfully request that CAISO publish the Generation Distribution Factors (GDFs) utilized in the definition of DGAPs and SGAPs, consistent with the way Load Distribution Factors are made available via the Market Participation Portal.

SP-Tie and GAP-Tie Modeling

In the CAISO Full Network Model (FNM) prior to June?2025, SP-Tie modeling always included an associated physical transmission line connected to the Scheduling Point (SP) in the FNM RAW file, and the intertie limit was enforced on that transmission line.

In the current FNM, the transmission line previously associated with the SP has been removed from the RAW file. Instead, the intertie limit is enforced directly on the SP injection capacity constraint. Please refer to the SP?Malin500 modeling topology shown below.

We have observed that, following the removal of the SP tie line, CAISO OASIS reports show Malin500 frequently binding with an “Intertie Constraint Shadow Price” in both the Day-Ahead Market (DAM) and Real-Time Market (RTM) (please see below). Is this outcome due to the application of a “logical transmission” representation on the SP capacity limit constraint?

In CAISO presentations, the examples do not explicitly illustrate binding conditions for the SP-Tie Malin500 configuration. Could the CAISO team provide example cases demonstrating SP-Tie and GAP-Tie Malin500 binding scenarios, and explain how the shift factor is determined for the Malin_5_101 congestion price calculation, in a future intertie modeling training session?

In addition, we would appreciate clarification on the following questions:

• Can a GAP-Tie be registered to specifically serve GHG-area (CAISO) load and submit bids with a GHG adder?
• Can a GAP-Tie be treated as a sink in the CRR auction market?

3. Please provide any additional feedback not already captured.

1. Please provide your organization's overall feedback regarding the Intertie Schedule Modeling Evolution on CAISO Interties presentation held on March 18, 2026.

Please see combined comments below.

2. Please provide your suggestions regarding areas of focus, issues and policy topics to discuss at upcoming workshops arising as a result of intertie schedule modeling design considerations.

Please see combined comments below.

3. Please provide any additional feedback not already captured.

Stakeholder Initiative Process Comments:

• Any Intertie Schedule Modeling changes made through this effort will have broad impacts to CAISO’s CRR and RA markets that extend beyond EDAM and will likely result in Tariff changes to either/both the CAISO’s and EDAM TSP’s OATTs; and therefore, should be classified as a stand-alone stakeholder initiative, with its own initiative page that ports over relevant content from the late-2025 EDAM Implementation stakeholder process that lead to the pending Tariff Clarifications filing.
• CAISO should begin exploration of Intertie Schedule Modeling enhancements by working with stakeholders to identify a problem statement and develop a set of common principles to guide developing near- and long-term solutions and should invite stakeholders to present concepts in a working-group format.
• CAISO should consider approaching this work as a two-phase effort, where Phase 1 targets near-term fixes to EDAM go-live functionality that were unable to be made as part of the recent Tariff Clarifications effort and Phase 2 targets long-term Intertie Scheduling Modeling policy enhancements that are aligned with a broader Transactional Seams management effort to support bilateral, market-participant initiated forward and spot-market contracting across bilateral-to-organized market and market-to-market seams.

Substantive Comments:

• From a first-principles perspective, CAISO should consider the increasing of power flow modeling precision in the day-ahead and hour-ahead intertie markets as a means to an end, not a standalone goal, and should not chase levels of precision in modeling forecasted power flows beyond the level of achievable accuracy in that forecast that exists given how markets external to the CAISO boundary operate.
• CAISO should review outcomes from its 2013-14 Full Network Model initiative with stakeholders, which initially included scope that would have introduced GAP-Tie like modeling for the CAISO BAA but was scaled back due to lack of stakeholder and Market Surveillance Committee support, and CAISO should explain what has changed in external market fundamentals that would now make the solution appropriate when it was not before if CAISO continues to pursue that functionality.
• CAISO’s explanation to date of the existing use of the GAP-Tie model in WEIM, as well as its use of that explanation to defend both its extension of GAP-Tie modeling to EDAM BAAs and its suggestion to extend it to the CAISO BAA, is incomplete and potentially misleading as it fails to acknowledge that the majority of power moving between BAAs within the WEIM footprint is sourced from non-participating or slice-of-system resources, scheduled and priced bilaterally to reflect the basis value of transmission rights, maintained as hourly-block non-market schedules from day-ahead to real-time, and flowed over point-to-point transmission rights not directly optimized by WEIM.
• Similarly, CAISO’s positing that GAP-Tie functionality is universal to organized markets is an incomplete and potentially misleading representation of the history of interchange modeling and interface pricing at the seams of bilateral and organized markets, and is largely irrelevant given the novel design of EDAM, the contract-path transmission foundations that it rests on, upcoming market-to-market seams challenges, and the need to maintain bilateral market functionality in the West for the foreseeable future.
• CAISO’s GAP-Tie modeling functionality set to be used for EDAM BAAs at go-live was not well explained by staff nor well understood by stakeholders in the 2022-23 EDAM proposal and stakeholder process around it, was never revisited in light of changes in EDAM Congestion Revenue Allocation policies updated in the CAISO Tariff in 2025, was not assessed for compatibility with EDAM TSP Congestion Revenue Allocation policies included in their 2025 Tariff filings, and was not tested for its potential to undermine contracting efficiency and distort market outcomes in the context of the expected end-state EDAM footprint.

Comments Regarding Principles for Assessing Intertie Schedule Modeling Enhancements:

• Ultimately, the determination of whether GAP-Tie modeling or SP-Tie modeling should be used for the CAISO BAA and/or the EDAM BAAs should be based on which model is most likely to produce efficient, reliable outcomes in the context of the well-functioning, bilateral intertie markets and CRR valuation practices that exist today, i.e., not whether one is right or better in the abstract but rather which is most useful in practice.
• CAISO and stakeholders should consider the physical role that intertie markets have played and will continue to play in both the day-ahead and hour-ahead horizon at its interties, including as a source of long-term RA capacity, and as a source of dispatchable spot-market liquidity that increases the flexibility of meeting CAISO demand and integrating VERs, and should consider that the EDAM BAAs need to have an intertie scheduling and pricing model in place that supports the same if EDAM is to provide meaningful benefits to participants – and consider that disrupting this functionality or failing to provide it to the EDAM BAAs will have outsized reliability impacts.
• CAISO and stakeholders should also consider the financial role of its intertie markets, including being a marginal resource in the day-ahead and hour-ahead market clearing during certain seasons, being an important source of bid and offer liquidity and provider of competitive supply that reduces market power potential and the need for mitigation, being a reference point for establishing scarcity pricing during tight system conditions, and being an economic hedging tool that works in concert with its CRR and convergence bidding markets to deliver least-cost outcomes for California LSEs – and should consider that disrupting this functionality or failing to provide it to the EDAM BAAs will have outsized economic efficiency impacts.

TEA Starting Position on Intertie Schedule Modeling Options:

• TEA was deeply engaged in the informal CAISO stakeholder working group process from August 2025 through January 2026 that ultimately lead to CAISO unwinding its plan to use the GAP-Tie model for its BAA at EDAM go-live and to inform the 2026 CRR Annual Auction, and below provides a list of materials it reviewed during that period, questions and feedback it provided to the CAISO in written comments, and concerns it has raised to both CAISO and PacifiCorp, in its EDAM Entity/BA role, regarding the impact of GAP-Tie modeling for the non-CAISO EDAM BAAs.
• TEA expects that post-go live review of market outcomes and market participant experience will most likely show that GAP-Tie modeling is incompatible with Western bilateral market forward contracting practices, the awarding of transmission rights by regional TSPs and use of those rights by counterparties, and the congestion hedging pathways for EDAM LSEs under the existing design, and that GAP-Tie modeling is incapable of meaningfully improving power flow modeling over the use of a simpler SP-Tie model to clear hourly day-ahead interchange schedules.
• TEA believes that similar outcomes, with a much greater magnitude of consequences, would occur for the CAISO region if CAISO were to move forward with GAP-Tie modeling for its BAA and therefore does not support transitioning away from the SP-Tie model for the CAISO BAA until both (1) significant enhancements have been made to the EDAM Congestion Revenue Allocation model and (2) Day-Ahead Markets have matured in the West to such an extent that coordinated market-to-market scheduling and congestion management functionality can be developed and adopted across all market regions.
• TEA therefore believes that the SP-Tie model should replace the GAP-Tie model for the non-CAISO EDAM BAAs through Tariff and BPM changes made as soon as possible but no later than Portland General Electric’s EDAM go-live on October 1, 2026, to address significant EDAM Congestion Revenue Allocation issues experienced by third parties, reduce disruptions to forward contracting for RA and RSE capacity, and support enabling non-resource specific economic interchange transactions at the EDAM BAA boundaries.

Note :: Given that TEA provides wholesale energy market services to LSEs across the entire Western Interconnect, TEA is also an active member of the SPP Markets+ and SPP RTO-Expansion stakeholder communities. TEA will be making parallel recommendations to those above regarding intertie schedule modeling and interface pricing through each market’s stakeholder processes and working groups. While each of those two markets have congestion revenue allocation frameworks that improve the hedging ability of market participants as compared to the EDAM model, the need to support and integrate bilateral market functionality still exists at their market borders the same as it does at CAISO’s. Further, TEA believes that developing this functionality near-term as consistently as possible across all day-ahead markets will naturally reduce the complexity of developing transactional seams solutions as soon as possible.

Relevant Prior TEA Comments and Questions Submitted to CAISO and PacifiCorp:

• CAISO EDAM Implementation Q/A Workshop Comments submitted November 2025:
  • https://stakeholdercenter.caiso.com/Comments/AllComments/47dc2bc6-758f-4753-8041-9362ed524ab9#org-5c7f2c45-ac78-484c-bab0-e0662947d95d
    • https://stakeholdercenter.caiso.com/Common/DownloadFile/ff9e8575-9914-4fdd-a28a-fb3d016768a4
  • https://stakeholdercenter.caiso.com/Comments/AllComments/47dc2bc6-758f-4753-8041-9362ed524ab9#org-09fb7c59-d55f-40db-a9b7-667a12b3a788
• CAISO Board / WEM GB Briefing on EDAM Implementation Details and Tariff Revisions Public Comment Letter submitted December 2025:
  • https://www.caiso.com/documents/tea-public-comment-letter-briefing-on-extended-day-ahead-market-and-day-ahead-market-enhancements-implementation-details-and-associated-tariff-revisions-dec-2025.pdf
• PacifiCorp Draft-Final EDAM Business Practices Comments submitted March 2026:
  • https://www.oasis.oati.com/woa/docs/PPW/PPWdocs/260306_BP_Draft_Final_Customer_Comments.pdf

Note :: As of April 1, 2026, the following comments and requests have not been responded to by PacifiCorp.

Excerpts from TEA / UAMPS’ Comments:

PacifiCorp’s BPs should address the Transfer Data Template (TDT) and its description of the financial location for import/export interchange. PacifiCorp’s BPs should also cover the process for entities to request Custom GAPs for resources/regions external to PACE/PACW.

See CAISO Draft BPMs: https://www.caiso.com/documents/extended-dayahead-market-business-practice-manual-draft.docx -- Section 22.8 – Interchange Schedules.

See CAISO Tariff Clarifications: https://www.caiso.com/documents/feb-6-2026-tariff-amendment-to-support-implementation-of-dame-edaminitiative-er26-1294.pdf  -- Appendix A and other.

PacifiCorp BPs should cover PACE/PACW ELAP definitions and process for entities to request Sub-LAP designations.

PacifiCorp BPs should cover the RA/RPS related import/export reassignment process described by CAISO in its EDAM Intertie Scheduling Readiness workshop and FAQ. See CAISO Tariff Clarifications: https://www.caiso.com/documents/feb-6- 2026-tariff-amendment-to-support-implementation-of-dame-edaminitiative-er26-1294.pdf -- Section 40.6.5.1 thru 40.6.5.4.

Stakeholders have requested CAISO provide the composition of the DGAP and/or a description of how that will be set for each DAM run for each DGAP referenced in the PacifiCorp TDT Point Mapping (see PacifiCorp OASIS).

Stakeholders have requested CAISO explore whether it is possible for PacifiCorp as the EDAM Entity to establish sub-DGAPs or some form of Custom GAPs (CGAP) to improve the model accuracy where adjacent BAAs cover a broad geographic area that is likely to have significant price separation between sub-zones. We believe it would be more efficient for this DGAP modeling enhancement to be done at the EDAM Entity level rather than having each LSE negotiate CGAPs, to the extent that is even possible [CGAPs are generally resource specific and meant to aggregate electrically similar resources, not establish a zonal reference]. Regardless, this activity should be covered in each EDAM Entity’s Tariffs or Business Practices, incorporating CAISO Tariff and BPMs by reference or owning the policy and practice outright.

Ex. 1 – PacifiCorp has mapped ten points of adjacency with the WACM BAA spanning from Wyoming (DJ/YTP) to Arizona (GlenCanyon2) that could logically be split into [at least] three zonal aggregations consistent with known WECC cut-planes.

Ex. 2 – PacifiCorp has mapped the MDWP intertie to the LDWP DGAP, however, the LDWP DGAP includes generation that is very remote to the PACE BAA and narrowing the DGAP to the IPP facility may more appropriately model import impacts at MDWP to the PACE system.

Ex. 3 – PacifiCorp has mapped two points of adjacency, Gonder and Red Butte, with the NEVP BAA that are likely to represent very different generation sources and load sinks as they are hundreds of miles apart and generally scheduled to/from distinctly different regions (PNW/NP-15 correlated source vs. DSW/SP-15 correlated source).

Relevant CAISO Stakeholder Initiative Background:

• CAISO 2020 Stakeholder Catalog Entry for FNM Phase 2:

This initiative would be the second phase of the Full Network Mode Expansion initiative implemented in fall 2014. That initiative provided reliability and market efficiency benefits by enhancing the CAISO’s modeling capabilities to account for unscheduled flows and enforce intertie power flow constraints in the day-ahead market. As part of this, the full network model topology was expanded to include information on resources, load, and interchange schedules in other balancing authority areas.

Phase 2 would explore modeling imports and exports into the CAISO balancing at their actual source and sink to improve the CAISO market’s modeling of actual electrical flow. Although the CAISO market currently uses an approximation of this for imports and exports to and from EIM areas, it currently models imports and exports to and from the CAISO balancing areas as point injections and withdrawals at the intertie scheduling point. Consistent modeling across the CAISO and EIM balancing areas would improve the market’s accuracy. For both the CAISO and EIM balancing areas, the initiative would likely consider the potential use of “scheduling hubs” as representations of import and export sources and sinks, e-tagging or settlement rule refinements, and remapping congestion revenue rights to scheduling hubs.

https://www.caiso.com/documents/2020finalpolicyinitiativescatalog.pdf - Section 6.1.20, Full Network Model Expansion – Phase 2 (C, 2).

• CAISO presentation to the CAISO Board on FNM Phase 1 functionality, February 2014: https://www.caiso.com/documents/decisionfullnetworkmodelexpansion-presentation-feb2014.pdf

• CAISO Board Memo on FNM Phase 1 functionality, February 2014: https://www.caiso.com/documents/decisionfullnetworkmodelexpansion-memo-feb2014.pdf

• CAISO MSC Opinion on FNM Phase 1 functionality, January 2014: https://www.caiso.com/documents/fullnetworkmodelimplementation-msc_opinionjan_2014.pdf

• CAISO summary of stakeholder comments: https://www.caiso.com/documents/decisionfullnetworkmodelexpansion-stakeholdermatrix-feb2014.pdf

• CAISO FNM Draft Final Proposal and Addendum:

https://www.caiso.com/library/full-network-model-expansion

• CAISO 2015 FNM Performance Report:

https://www.caiso.com/documents/discussion-fullnetworkmodelperformance-presentation-feb2015.pdf

1. Please provide your organization's overall feedback regarding the Intertie Schedule Modeling Evolution on CAISO Interties presentation held on March 18, 2026.

WPTF appreciates CAISO’s efforts to provide a clear and educational overview of intertie schedule modeling approaches, including the comparison between the existing SP-Tie framework and the transition to GAP-Tie modeling. The workshop demonstrated that GAP-Tie modeling can improve the engineering representation of power flows by better aligning modeled transactions with the physical system and enhancing congestion identification, assuming the source of energy is more accurately represented than under SP-Tie. However, GAP-Tie modeling still requires assumptions in the day-ahead timeframe regarding the source of imports.

WPTF also notes that the concerns we raised during the 2025 EDAM implementation workshops stem from a market perspective, and we appreciate the opportunity to clarify them here. Our concerns are distinct from, and not in disagreement with, the engineering benefits of improved power flow modeling that CAISO emphasized during those discussions. Improved power flow modeling is an engineering enhancement and does not necessarily result in improved market outcomes.

WPTF remains concerned that the current discussion focuses primarily on modeling improvements without sufficiently addressing their impact on market efficiency and reliability. While improved modeling enhances the system’s ability to identify congestion and constraints, efficient market outcomes also require that the market can respond to those signals through economic dispatch. If intertie modeling changes are paired with reduced intertie bidding or increased reliance on self-scheduling, the market’s ability to observe costs and select least-cost resources is diminished. In these cases, prices may still be calculated, but they become less meaningful and less connected to actual dispatch decisions.

This issue is particularly important in the day-ahead market, which is largely financial. Both SP-Tie and GAP-Tie approaches rely on assumptions about the source of imports, and improved modeling does not eliminate this uncertainty. Without cost visibility through economic offers, more precise modeling does not necessarily lead to improved price formation or dispatch efficiency.

For these reasons, WPTF encourages CAISO to evaluate intertie modeling changes holistically, considering impacts on economic dispatch, price formation, and market efficiency alongside improvements in modeling accuracy.

2. Please provide your suggestions regarding areas of focus, issues and policy topics to discuss at upcoming workshops arising as a result of intertie schedule modeling design considerations.

WPTF recommends that future workshops expand beyond the engineering aspects of modeling design to more directly address how these changes affect market outcomes. In particular, CAISO should examine the relationship between improved modeling accuracy and the market’s ability to achieve least-cost dispatch. It will be important to understand whether more precise congestion identification leads to better outcomes in practice, especially in cases where economic participation is limited.

A key area of focus should be the role of intertie bidding and cost visibility. If intertie bidding is reduced or removed, or if participation shifts toward self-scheduling, the market’s ability to observe marginal costs and respond efficiently to price signals is diminished. This raises important questions about how price formation and dispatch outcomes will be affected under the GAP-Tie design.

Workshops should also examine how these modeling changes impact alignment between the day-ahead and real-time markets. While GAP-Tie modeling is intended to better reflect physical flows, it is important to assess whether it meaningfully improves convergence between day-ahead schedules and real-time operations, given the continued reliance on assumptions about import sourcing.

In addition, WPTF encourages CAISO to provide more complex and realistic examples in future discussions. The examples presented in the workshop, particularly those focused on transactions sourced from PAC, were helpful for illustrating basic concepts but do not fully capture the diversity and complexity of real-world intertie transactions.

3. Please provide any additional feedback not already captured.

WPTF requests that CAISO create a dedicated initiative page for this effort rather than include it within the broader EDAM policy page. While this topic is related to EDAM, the existing page aggregates materials from multiple policy efforts, making it difficult to track this specific discussion. A standalone page would improve transparency and ease stakeholder engagement. We note similar concerns with the EDAM Congestion Revenue Allocation effort and recommend a separate initiative page for that topic as well.