California grid operator launches its extended day-ahead market with PacifiCorp

The California Independent System Operator launched on May 1 the first day-ahead market expansion into the Western Interconnection outside of an organized market, with PacifiCorp as the first participant.

CAISO's Extended Day-Ahead Market will optimize the use of existing transmission and resources in the much larger day-ahead timeframe across an expanded Western footprint, according to CAISO.

"EDAM strengthens regional coordination, helps us use the grid more effectively and supports lower cost outcomes for customers," Ryan Flynn, president of Pacific Power, a division of PacifiCorp, said during a May 1 press conference.

By expanding regional coordination into the day-ahead timeframe, when most electricity deliveries are planned, EDAM will leverage the West's diverse resource mix and increasingly interconnected transmission system, according to CAISO. Larger-scale and regionally coordinated day‑ahead planning allows operators to make more optimized resource commitments and transmission usage across major supply and load centers, to better prepare the system to meet real‑time needs, improving both efficiency and reliability.

"The successful launch of EDAM marks the next chapter in the evolution of a geographically diverse and electrically connected Western electricity market," CAISO President and CEO Elliot Mainzer said at the press conference.

EDAM builds off the platform of the Western Energy Imbalance Market that's been in place since 2014, Mainzer added.

"Although there are some significant new features of the Extended Day-Ahead Market and quite a bit of additional data transfer and, of course, you're bringing on a new imbalanced reserve product, I do think that that experience and the familiarity with the platform have been very valuable," Mainzer said.

CAISO COO Mark Rothleder said, although there are some minor data issues to address with the EDAM launch, "The transition to the EDAM market and WEIM has gone very smoothly."

"We knew there were a few things we would have to watch and continue to enhance, so we had plans in place for these," Kerstin Rock, PacifiCorp managing director for western market policy and analytics, said.

Market impact

"Our expectation is that we'll unlock some really high value trading opportunities right off the bat," Advanced Energy United's Senior Director Brian Turner said about the impact of EDAM for market participants. "We'll also see an increase over time that may be slower to develop... perhaps we'll see more transmission offered up and that will expand the range of opportunities."

The immediate high-value opportunities include Wyoming wind and Utah resources moving into California during peak times or overnight, as well as California solar moving into the rest of the western region when it is very low cost, Turner said.

CAISO wholesale spot power prices for May 1 delivery trended lower year over year. NP15 on-peak day-ahead locational marginal price stood at $14.37/megawatt-hour, 34% lower than the May 2025 average, while SP15 on-peak day-ahead LMP was $4.91/MWh, 67% lower than the year-ago average, according to CAISO data.

In December 2023, the US Federal Energy Regulatory Commission approved CAISO's EDAM and Day-ahead Market Enhancement tariff filing.

What's next

"The success that is starting today is something that will convince people around the West that really the value here is just too much to pass up," Turner said. "Lots of folks are watching exactly how well it functions, just the basic operations of the market."

Portland General Electric plans to enter EDAM later in 2026. Slated to join in 2027 are Public Service Company of New Mexico, Turlock Irrigation District, Los Angeles Department of Water and Power, and Balancing Authority of Northern California, followed by Imperial Irrigation District in 2028.

Entities that are leaning towards EDAM include Idaho Power, NV Energy, and PowerWatch, formerly BHE Montana.

Western expansion

CAISO is not the only grid operator expanding day-ahead offerings across the Western footprint. The Southwest Power Pool is developing Markets+, which is scheduled to launch in 2027.

Western Freedom, a nonprofit group that advocates deeper market integration in the West, has argued that the EDAM's footprint must be geographically broad to maximize consumer benefits.

"If we're really going to see those affordability benefits, we have to keep this footprint together or make it as big as possible," Kathleen Staks, Western Freedom executive director, said during an April 30 discussion in Santa Barbara, California, hosted by WIRES, a transmission-focused industry trade group.

Staks said addressing lingering concerns about the EDAM's governance structure will ultimately impact "what the footprint looks like in the West."

The planned rollout of two day-ahead products in the Western Interconnection was initially "healthy at the beginning, but has turned more challenging of late," Staks said. "I endearingly call it the Market+ 'island chain,' because if you think about these potential market participants, they're not connected. They match up beautifully, but you've got to run that all the way through entities that are going to be joining EDAM, so that's creating some challenging seams issues."

Finding consensus on a regional resource adequacy program will be another top priority for EDAM participants going forward, Staks said.

Broader West market work

FERC in February 2023 approved the region's first voluntary resource adequacy program, the Western Resource Adequacy Program, which is set to become financially binding in the winter 2027/2028 season. Under the program, participants outline the resources they plan to use to serve the load, and that capacity is counted using common rules. Financial penalties will be assessed for participants who are short on capacity for the upcoming season.

However, PacifiCorp, NV Energy, and PNM were among a handful of core EDAM participants who announced in October 2025 that they intend to exit WRAP due to concerns about the program's penalty structure, among other considerations.

The broader Western power market view also includes the West-Wide Governance Pathways Initiative, which was launched in the summer of 2023 by a coalition of regulators from five Western states. The goal is to offer tariff-level and policy-level evolution of the energy markets, and then have CAISO implement and execute the technical aspects. The Pathways Launch Committee, which Staks co-chairs, adopted on Dec. 12, 2025, the official incorporation documents for the new Regional Organization for Western Energy, an independent governing body that will soon govern EDAM.

On April 28, 2026, ROWE convened the first of a series of workshops to explore an alternative EDAM-aligned resource adequacy solution.

"This is the first one of these additional services that we envisioned for the future of the ROWE," Staks said. "This new independent governance is something that opens the door to more western regional services than we've had previously."

Where it started

EDAM builds on the benefits of the WEIM, a real-time market which includes 22 balancing authorities across 11 western states, representing 80% of the demand for electricity in the Western Interconnection, according to CAISO. PowerWatch and Black Hills are currently in parallel operations in preparation for their onboarding to the real-time market next week. Imperial Irrigation District is expected to join in 2028.

PacifiCorp was also the first participant in the WEIM and has generated more than $1.1 billion in benefits for its customers, according to quarterly market benefit reports.

"WEIM and EDAM have proven they are solutions to greater reliability and affordability for electricity customers," Mainzer said. "That's really what this has always been about, and that's what it's going to continue to be about."