WEIM benefits report shows another historic milestone

Contact: ISOMedia@caiso.com

Follows robust regional energy transfers during recent cold weather

FOLSOM, Calif. – The latest quarterly benefits report for the Western Energy Imbalance Market (WEIM), coming about two weeks after regional energy transfers helped keep the lights on during an extreme cold spell in parts of the West, shows more than $5 billion in cumulative benefits for market participants since the market was launched.

“Working collaboratively with our partners across a broad geographic footprint is not only producing significant financial benefits for utilities and their customers,” Elliot Mainzer, president and CEO of the California Independent System Operator said. “It is also playing a key role in maintaining system reliability during extreme weather events.”

During the fourth quarter of 2023, the WEIM’s 22 participants attained $391.82 million in cost-saving benefits, pushing the total savings across California and the West to $5.05 billion since the market was launched in late 2014. 

“The market’s performance in 2023 shows how widespread cooperation among entities in the Western Interconnection reduces consumer costs and quickly sends energy where it is most needed during stressed weather conditions,” said WEIM Governing Body Chair Andrew Campbell.

The WEIM’s quarterly benefits reports don’t address reliability directly, focusing instead on financial savings and the environmental benefits that come from finding excess clean power at risk of curtailment and moving it across the West. Since 2014, the report points out, the real-time electricity market has reduced greenhouse gas emissions by more than 925,568 metric tons, or the equivalent of taking more than 194,597 passenger cars off the road for one year.

Among other things, the WEIM enables participating entities to buy and sell power close to the time electricity is generated and consumed. Using state-of-the art technology, the market finds and delivers lowest-cost resources to meet immediate power needs and manages congestion on transmission lines to maintain grid reliability.

But the market’s reliability benefits are also impressive. During the past two summers, utilities in California and across the West have benefitted from the ability of the WEIM to efficiently transfer power during extreme events by leveraging the resource diversity and transmission connectivity that exists across the broader region.

The value of market coordination was shown again during the extreme cold that swept through the Pacific Northwest during the long Martin Luther King, Jr. holiday weekend January 13-15. 

During that event, WEIM transfers from California and the Southwest effectively helped in meeting demand across the region in those Western balancing authority areas that needed assistance.

“There has been a lot of focus on the economic value of our market, and justifiably so,” Mainzer said. “But the reliability value of the WEIM is potentially significantly greater than the economic value as the grid becomes more impacted by extreme weather events and an ever-changing resource mix.”

The 2023 Q4 economic benefits by participant are as follows: 


             (millions $)

Arizona Public Service$  11.13 
AVANGRID Renewables$    6.64
Avista $    4.30  
Balancing Authority of Northern California$  73.12 
Bonneville Power Administration$    9.68
California ISO$  25.40 
El Paso Electric $    4.00
Idaho Power$    9.47  
Los Angeles Department of Water & Power$  39.10 
NV Energy$  22.46 
NorthWestern Energy$    7.57  
PacifiCorp$  50.46 
Portland General Electric$  11.58 
Public Service Company of New Mexico$    6.17  
Puget Sound Energy$  15.17 
Powerex$   43.96
Seattle City Light$    3.65  
Salt River Project$  22.03 
Tacoma Power $    2.80  
Tucson Electric Power$    5.90
Turlock Irrigation District$    1.06  
WAPA Desert Southwest$  16.17


Building on the proven success of the WEIM, the ISO has collaborated with Western stakeholders to develop an Extended Day-Ahead Market (EDAM) that enables entities participating in the WEIM to benefit from optimized and efficient commitments in the day-ahead market to meet next-day demand, where the majority of energy transactions occur. For more information, view the EDAM fact sheet.

For more information visit the WEIM website.


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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 consumers. It 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 $9 billion competitive electricity market. Recognizing the importance of the global climate challenge, the ISO is at the forefront of integrating renew able power and advanced technologies that w ill help provide a sustainable energy future efficiently and cleanly.  

The Western Energy Imbalance Market (WEIM) is a real-time wholesale energy trading market that enables participants anywhere in the West to buy and sell energy w hen needed. The WEIM Governing Body is the governing authority designed by regional stakeholders and has shared authority with the ISO Board of Governors to resolve rules specific to participation in the WEIM.

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