WEIM Posts Strong Q2, Surpassing $7.4 Billion in Total Benefits
FOLSOM, Calif. — The Western Energy Imbalance Market (WEIM) delivered more than $420 million in economic benefits to participants in the second quarter of 2025, pushing total cumulative savings to $7.41 billion since the market’s launch in 2014.
Operated by the California Independent System Operator (ISO), the WEIM enables utilities and balancing authorities across the West to buy and sell electricity in real time, improving grid efficiency and reducing costs for customers.
The 2025 second-quarter economic benefit for each participant is shown below:
| Participants | (millions $) |
|---|---|
| Arizona Public Service | $ 11.21 |
| AVANGRID Renewables | $ 13.52 |
| Avista | $ 2.42 |
| Balancing Authority of Northern California | $ 35.86 |
| Bonneville Power Administration | $ 5.81 |
| California ISO | $ 27.18 |
| El Paso Electric | $ 3.07 |
| Idaho Power | $ 11.15 |
| Los Angeles Department of Water & Power | $ 32.17 |
| NV Energy | $ 84.12 |
| NorthWestern Energy | $ 19.33 |
| PacifiCorp | $ 33.02 |
| Portland General Electric | $ 9.49 |
| Public Service Company of New Mexico | $ 48.96 |
| Puget Sound Energy | $ 11.94 |
| Powerex | $ 7.28 |
| Seattle City Light | $ 11.90 |
| Salt River Project | $ 30.01 |
| Tacoma Power | $ 6.36 |
| Tucson Electric Power | $ 4.36 |
| Turlock Irrigation District | $ 0.84 |
| WAPA Desert Southwest | $ 10.44 |
| Total | $420.44 |
The quarterly benefits report measures cost savings to participants, including market efficiencies and environmental benefits such as the displacement of more expensive generation with renewable resources. The WEIM has now helped participants avoid emissions of more than 1.12 million metric tons of CO2 since its launch, roughly equal to emissions from 236,276 passenger cars driven for a year.
The market also enhances reliability across the region by facilitating the transfer of electricity among market participants to where and when it is needed the most.
Looking ahead: Extended Day-Ahead Market (EDAM)
The latest quarterly report highlights the value of the ISO’s Extended Day-Ahead Market (EDAM), scheduled to launch in 2026. EDAM is poised to build on the benefits of WEIM for participants in the day-ahead market, where the vast majority of energy trading occurs. In a key milestone for EDAM development, Public Service Company of New Mexico (PNM) recently announced its commitment to join the market in 2026. PNM’s participation satisfies the Phase 1 trigger for EDAM implementation, marking a significant step forward in expanding regional coordination and unlocking additional economic and operational benefits for participants.
About the WEIM
Since its launch in 2014, the WEIM has expanded to include 22 balancing authorities across 11 western states, representing 80% of the demand for electricity in the Western Interconnection. The California ISO is a balancing authority and not a market participant; the benefits estimated for the California ISO balancing authority area accrue to its market participants, not the California ISO Corporation. Today, the WEIM footprint includes portions of Arizona, California, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming, Texas, and extends to the border with Canada.
For more information about the Western Energy Imbalance Market and the Extended Day-Ahead market visit the Western Energy Market website.
# # #
California ISO | 250 Outcropping Way | Folsom, CA 95630 | www.caiso.com
The California Independent System Operator (ISO) is a nonprofit public-benefit corporation dedicated with its partners to continuous improvement and secure operation of a reliable grid operated for the benefit of electricity consumers.
The ISO provides comprehensive grid planning, open and nondiscriminatory access to one of the largest networks of high-voltage transmission power lines in the world, and operates a competitive electricity market that in 2024 included $16.1 billion in transactions. In helping to carry out California’s energy policy objectives, the ISO is at the forefront of integrating renewable power and advanced technologies that will help provide a reliable and sustainable energy future efficiently and cleanly.
The Western Energy Imbalance Market (WEIM) is a real-time wholesale energy trading market that enables participants throughout the West to buy and sell energy when needed. Since its inception in 2014, it has resulted in more than $7 billion in financial benefits to market participants and their customers and has enhanced reliability across the region by sharing diverse resources and optimizing inter-connected transmission. The Western Energy Markets Governing Body, designed by regional stakeholders, has primary decision-making authority regarding rules specific to participation in the WEIM and Extended Day-Ahead Market.