The Extended Day-Ahead Market took center stage at CAISO in 2025 as the ISO tabled other long-term initiatives to ensure the market’s timely launch in May 2026 with PacifiCorp as its first participant.
And EDAM preparations will continue to be the primary focus for the ISO and its stakeholders heading into the new year.
According to a December report from CAISO CEO Elliot Mainzer, 2025 saw thousands of stakeholders from California and throughout the West tune in to EDAM implementation workshops that enlightened and sometimes perplexed stakeholders, with the ISO trying to quickly address new critical problems to keep EDAM’s schedule intact.
The year started with a bang: In February, Powerex — which has committed to joining SPP’s competing day-ahead market Markets+ — published a paper contending that EDAM contained a “design flaw” that could result in $1 billion in unjustifiable charges for non-CAISO participants.
The paper said EDAM’s treatment of firm transmission rights and congestion would leave the market’s non-CAISO participants exposed to charges for constraints occurring outside their systems while not providing them adequate ability to recover or hedge against those costs. (See Powerex Paper Sparks Dispute over EDAM ‘Design Flaw’.)
About a month later, CAISO began an “expedited” initiative to decide how to allocate congestion revenues when a transmission constraint in one EDAM balancing authority area causes congestion in a neighboring BAA. (See Fast-paced Effort will Address EDAM Congestion Revenue Issue.)
In late summer, FERC approved CAISO’s new EDAM congestion revenue allocation design. The approved design is a short-term solution, and the ISO said it would propose a long-term design within the next two years. (See CAISO’s EDAM Scores Simultaneous Wins at FERC.)
Top EDAM Challenges
RTO Insider asked CAISO and a few of its stakeholders their views on EDAM’s top challenges in 2025.
CAISO Vice President of External Affairs Stacey Crowley said the ISO worked with vendors to deliver timely functionality for market simulation, supported participating entities in developing tariffs through the FERC process, and established a transitional congestion revenue allocation design informed by stakeholder input — all critical steps to enable EDAM launch.
PacifiCorp, which will join EDAM in May 2026 as the first participant, said it faced several key challenges while preparing for EDAM’s 2026 launch.
“Building and testing interconnected IT systems for PacifiCorp and CAISO required extensive coordination and design adjustments that had to be integrated into the development plans of both organizations,” PacifiCorp spokesperson Omar Granados told RTO Insider. “Additionally, managing communication and testing across numerous transmission customers and 14 neighboring utilities added significant logistical challenges.”
EDAM Priorities Going into 2026
The coming months in 2026 will see heightened activities around EDAM implementation, with stakeholders anticipating several challenges to ensure the market opens as planned in May.
PacifiCorp remains confident in the EDAM go-live timeline, but it must resolve issues that have never been encountered before, Granados said.
For example, starting in February, PacifiCorp and CAISO will begin parallel operations for their respective market systems, staff and support processes. While the ongoing market simulations have suggested that the utility is ready for EDAM, parallel testing will “likely reveal adjustments needed before launch,” the spokesperson said.
To address this concern, PacifiCorp is working closely with software partners and has established an internal issue-resolution team to quickly identify and resolve problems, Granados said. After starting in the market, further refinements and process optimizations are expected, he said.
CAISO’s Department of Market Monitoring (DMM) will be “closely watching and reporting on” critical areas as EDAM is implemented, DMM Executive Director Eric Hildebrandt said. One area is market efficiency and performance, such as pricing and volumes of self-scheduling versus supply/demand that is bid into and clears EDAM. DMM will watch also how EDAM affects the broader real-time Western Energy Imbalance Market.
DMM will monitor congestion withing EDAM, specifically how much transmission is available in the day-ahead market for transfers between BAAs; the amount of “unscheduled flows” and congestion revenues created by schedules in one BAA on other BAAs; and how these congestion costs and revenues are allocated among BAAs, Hildebrandt said.
Two other focuses for EDAM: the day-ahead resource sufficiency requirement and evaluation, and the day-ahead imbalance reserve product, including the impact it has on EDAM prices, he said.
As for CAISO, Crowley said the ISO will work with vendors to test systems and procedures, and to ensure market participants have the training and practices needed to fully engage at launch.
Working Across Agency Lines
RTO Insider asked CAISO how it plans to work with the California Energy Commission and the California Public Utilities Commission as EDAM launches.
Crowley noted that EDAM is regulated under FERC, but “we have worked collaboratively with California agencies such as the CEC and CPUC — as well as regulators across the West — to ensure they are informed and able to provide input into the market design.”
“There is an important role for state regulators through the [Western Energy Markets] Body of State Regulators and the public stakeholder process,” she said. “While state agencies do not have direct oversight of EDAM, they have also been actively engaged in the development of legislation like Assembly Bill 825, which will establish an independent governance board, committee of state regulators and other public processes similar to what occurs at … CAISO now.”
DMM will publish quarterly, annual and other special reports on the performance of CAISO markets, with state regulators and policy makers being a primary audience for those documents and the recommendations they contain.
“We do outreach to key regulatory agencies in all the EDAM/WEIM states in order to highlight our reports and recommendations, answer questions and get any input state agencies have on what types of analysis and reporting they would find most useful,” Hildebrandt said.
While DMM’s recommendations often play a role in shaping market design, “we do not have any role in the actual implementation,” Hildebrandt added. Instead, the Monitor “will be focusing on quickly identifying and helping address any problems or unexpected issues that arise” with EDAM implementation, he said.
Batteries Provide Sneaky Reliability, Kinks to Work Out
While EDAM implementation demanded much of the ISO’s and stakeholders’ attention in 2025, CAISO weathered yet another year without needing to issue a flex alert or call for rolling blackouts. CAISO leaders repeated highlighted the addition of massive volumes of battery storage resources as a critical contributor to grid reliability.
By April 2025, more than 12,000 MW of battery storage capacity was online in the ISO — up from about 500 MW in 2020. An additional 15,000 MW of storage resources are expected by 2028, accounting for the majority of the 20,000 MW of new resources expected in that time.
The increase in batteries has kept CAISO focused on technical issues throughout the year, such as outage management enhancements, battery nonlinearity guidance and state of charge clarifications. The ISO also started an initiative to improve the visibility of distributed batteries, especially when they are needed for resource adequacy purposes.
CAISO will continue to lean on batteries in the coming year, specifically in the ISO’s resource adequacy program and qualifying capacity (QC) process. Stakeholders asked CAISO to provide more clarity on how battery durations will be counted in CAISO’s default QC counting rules, asking the ISO to avoid lumping all battery capacity together, including eight-hour batteries and four-hour batteries.
CAISO’s DMM early in 2025 raised concerns about the potential gaming and inefficient bidding behavior in CAISO’s bid cost recovery (BCR) process for battery storage resources. In an August report, DMM said the current BCR design creates gaming opportunities for battery storage units, “especially through manipulation of various biddable parameters used to manage state-of-charge. (See CAISO Monitor Sees ‘Gaming’ Potential in Battery Storage Bid Cost Recovery.)







