The California ISO’s Western Energy Imbalance Market (EIM) is a real-time bulk power trading market, the first of its kind in the western United States. EIM’s advanced market systems automatically find the lowest-cost energy to serve real-time customer demand across a wide geographic area. Utilities will maintain control over their assets and remain responsible for balancing requirements while sharing in the cost benefits the market produces for participants.

Since launching in 2014, the Western EIM has enhanced grid reliability and generated cost savings in the millions for its participants. Besides its economic advantages, the EIM improves the integration of renewable energy, which leads to a cleaner, greener grid.

EIM is governed by a five member body with delegated authority over rules specific to the Western EIM.



Frequently asked
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Preguntas Comunes
Sobre el EIM >>


Quarterly benefits &
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Balancing Authority of Northern California/SMUD – entered 2019

Idaho Power Company – entered 2018

Powerex – entered 2018

Portland General Electric – entered 2017

Puget Sound – entered 2016

Arizona Public Service – entered 2016

NV Energy – entered 2015

PacifiCorp – entered 2014

California ISO – entered 2014



Los Angeles Department of Power & Water – entry 2020

Salt River Project – entry 2020

Seattle City Light – entry 2020

Public Service Company of New Mexico – entry 2021

NorthWestern Energy – entry 2021

Implementation documents

Market notices

Western EIM active and pending participants