So far, so good.
That’s the consensus takeaway through the first few days of operation of the Extended Day-Ahead Market, or EDAM, the new voluntary market launched by the California Independent System Operator (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, EDAM 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 market is producing “robust and stable results,” according to Jayme Ackemann, CAISO’s head of communications. On Tuesday, all participants passed 100% of the Resource Sufficiency Evaluation (RSE), enabling the transfer of 600 megawatts (MW) across the system. The RSE is a mandatory, day-ahead, real-time check designed to ensure that participating balancing authority areas (BAAs) have enough power supply to meet their own customer demand before they can lean on neighboring grids for energy.
“Based on these early results, we continue to be very pleased with the market’s performance,” shared Ackemann in her daily update.
“The successful launch of EDAM marks the next chapter in the evolution of a geographically diverse and electrically connected Western electricity market,” predicted Elliot Mainzer, president and CEO of the ISO.
“By working together, we are delivering greater reliability and affordability for energy consumers across the region, and we remain committed to continually strengthening the market to meet the challenges and opportunities facing the Western grid.”
How Does the EDAM Work?
The EDAM was developed through a collaborative and highly iterative stakeholder process that engaged utilities, regulators, and a broad range of regional energy interests. It is a voluntary market that preserves the autonomy of balancing authorities while accommodating the West’s diverse policy and planning frameworks. Participation decisions are made independently by each entity.
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).
If this sounds a little familiar…
The new market builds upon what works in the Western Energy Imbalance Market (WEIM), which runs every 5 and 15 minutes. Since its launch in 2014, the first-of-its-kind real-time market has balanced electricity supply and demand, enabling the use of the lowest-cost energy across its large, interconnected footprint, enhancing grid reliability and generating significant cost savings for its participants. Since joining the WEIM when it launched, PacifiCorp reports more than $1.1 billion in benefits for its customers, according to quarterly market benefit reports.
EDAM is the day-ahead extension of WEIM. While the WEIM clears real-time imbalance only, EDAM promises day-ahead commitment, the market process that clears the bulk of CAISO’s energy. Balancing authority areas that participate in the EDAM, like PacifiCorp, still balance in real time through WEIM, ensuring the amount of electricity produced matches the amount customers are using. CAISO will continue to fully support participation in the WEIM regardless of whether entities choose to join EDAM.
The WEIM currently includes 22 participating entities across 11 states, representing about 80% of electricity demand in the West. Black Hills Energy and PowerWatch (formerly BHE Montana) are scheduled to join shortly, bringing South Dakota into the market as the 12th participating state. California’s Imperial Irrigation District (IID) has committed to join both WEIM and EDAM in 2028.
Since its launch, the WEIM has generated more than $8.6 billion in benefits for participating utilities and their customers, largely by reducing unnecessary production costs through efficient energy transfers. Those transfers have strengthened reliability by enabling regions with excess supply to assist areas navigating grid stress attributed to extreme weather, wildfires, or other emergencies, while simultaneously reducing emissions.
Cost-benefit analysis commissioned by Portland General Electric (PGE) concluded that EDAM is likely to provide greater economic benefits than alternative market options. By joining the EDAM, PGE anticipates gross cost savings of $6 million to $18 million annually, based on current modeling, depending on the final number of EDAM participants.
Who Will Participate in the EDAM?
PacifiCorp, headquartered in Portland, Oregon, is a day one participant, as previously noted. The utility lends significant gravitas, as it owns and operates the largest privately owned transmission system in the Western United States and boasts roughly 12 gigawatts (GW) of generation capacity. PacifiCorp operates across two balancing authority areas and serves 2.1 million customers through its two retail divisions: Pacific Power in California, Oregon, and Washington, and Rocky Mountain Power in Idaho, Utah, and Wyoming. In addition to balancing electricity supply and demand for about 80% of California and part of Nevada, the ISO operates the real-time Western Energy Imbalance Market, EDAM, and RC West, which is the reliability coordinator for the bulk electric system across a large portion of the Western United States.
EDAM will add new participants soon. PGE has signed an implementation agreement and is scheduled to join in October 2026.
Additional utilities have also signed the dotted line plan to join EDAM in 2027, including the Los Angeles Department of Water and Power (LADWP), the Balancing Authority of Northern California (BANC, which includes the Sacramento Municipal Utility District, or SMUD), the Public Service Company of New Mexico (PNM), and the Turlock Irrigation District (TID). Once these entities are onboarded, EDAM will serve approximately 42% of electricity demand in the West, according to data from the North American Electric Reliability Corporation (NERC).
The IID will join in 2028, as will NV Energy, Nevada Power Company, and PowerWatch. Several other Western utilities are currently evaluating participation, including Idaho Power. Seattle City Light (SCL) will throw its hat into the mix in 2029.
Bonneville Power Administration (BPA), currently a WEIM participant, chose Markets+ over EDAM in March 2025. A Brattle Group report determined that joining EDAM would’ve created the largest customer savings for the BPA Balancing Authority Area of all options, more than $65 million per year. By electing not to join EDAM, the Northwest federal hydro pool, which BPA operates across 31 federal dams and 75% of the Northwest’s high-voltage transmission, remains outside EDAM.