The California ISO (CAISO)-managed Extended Day-Ahead Market (EDAM) has secured the formal commitment of its eighth member, BHE Montana.
The Great Falls, MT-headquartered energy producer, operator, and services provider began participating in the Western Energy Imbalance Market (WEIM) this year and will join the EDAM in 2028.
“The benefits already demonstrated through BHE Montana’s participation in the WEIM show the value regional coordination can deliver for customers,” said Ed Rihn, CEO of BHE Montana. “EDAM builds on that foundation by extending those efficiencies into the day-ahead timeframe, creating additional opportunities to access lower-cost resources, better manage system conditions, and support reliable electric service for Montana customers and across the region.”
Participation in the EDAM will grant BHE Montana access to a broader regional marketplace that helps power producers and transmission providers plan and schedule energy resources one day in advance. By coordinating with a larger network of participants across the West, BHE Montana will improve the state’s access to affordable energy supplies, make more efficient use of current and planned transmission infrastructure, and enhance overall system reliability.
The EDAM is the new voluntary market launched by the CAISO and day-one cornerstone participant PacifiCorp on May 1.
The EDAM aims to reduce electricity costs for millions of customers by helping balancing authorities across the Western United States plan and schedule one day in advance through a shared market system. Instead of each participant or utility having to accommodate the needs of its own territory, the EDAM helps the region coordinate and satisfy demand through the lowest-cost available mix of power plants and transmission. By expanding regional coordination into the day-ahead timeframe, when most electricity deliveries are planned, the market leverages the West’s diverse resource mix and increasingly interconnected transmission system to empower operators to make more optimized resource commitments and transmission usage across major supply and load centers, improving both efficiency and reliability.
The EDAM is built on a technology platform that helps minimize entry costs, includes no exit fees, and uses a daily resource-sufficiency evaluation compatible with the range of resource-adequacy programs used across the West. It supports efficient energy transfers across existing transmission lines and compliance with multiple state greenhouse gas regulatory programs. The EDAM design and related tariffs have been approved by the Federal Energy Regulatory Commission (FERC).
Since going live, CAISO’s EDAM has delivered a range of positive outcomes, including efficient price formation, interregional trade, and strong resource sufficiency results across the participating balancing areas, boosting summer reliability. Regional reliability has been strengthened by the addition of about 36,000 megawatts (MW) of new grid resources in California since 2020, including more than 17,000 MW of battery storage capacity. This has enabled significant exports from the ISO footprint during what has been a record-setting summer for peak demand in the Western Interconnection.
Learn more about the Extended Day-Ahead Market here.
The recently released inaugural Western Energy Markets Quarterly Benefits Report underscores the value of regional coordination between energy providers. CAISO’s expanded publication combines the longstanding WEIM quarterly benefits analysis with the first results from the EDAM, reflecting the continued evolution of Western markets. The new report provides a more comprehensive view of the economic, environmental, and reliability benefits delivered to market participants across the region.
In the second quarter of 2026, the WEIM delivered approximately $459.7 million in gross economic benefits, pushing cumulative cost savings for market participants and their customers to more than $9.08 billion since the market launched in 2014. The EDAM delivered $11.38 million in benefits during its first two months of operation, shared among its first participants: PacifiCorp East, PacifiCorp West, and CAISO. Portland General Electric is scheduled to begin trading energy in the day-ahead market in October.
“The Western electricity sector has entered a new era of regional collaboration,” said Elliot Mainzer, CAISO president and CEO. “As participation in our energy markets continues to grow, this expanded quarterly report provides stakeholders with a clearer picture of the economic and reliability value these markets create for electricity consumers across the West.”
For BHE Montana’s balancing area, benefits have eclipsed $2 million since joining WEIM in May 2026, reinforcing the promise of additional customer value as day-ahead coordination expands across the West.
“It’s exciting to see BHE Montana committed to both the real-time and day-ahead markets,” added Mainzer. “As EDAM continues to grow, more communities across the West will benefit from a proven platform that enhances reliability and supports affordability.”
