Western Energy Imbalance Market (WEIM)

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An Electricity Market That’s Bigger Than the Weather
The size and configuration of day-ahead markets in the West will greatly impact electricity bills and grid reliability, says the Environmental Defense Fund.
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‘Widespread Support’ for CAISO’s $8.5M ROWE Funding Plan
CAISO is moving toward approval of an $8.5 million financing plan for the Regional Organization for Western Energy’s start-up costs.
CAISO
CAISO Looks to Improve Data Quality from Solar, Wind, Battery Resources
CAISO is proposing new methods to address “poor quality data” from some variable energy resources in the region in order to improve grid forecasting, the ISO said in a straw proposal.
CAISO DMM
Battery Capacity, Coal Use Rise in WEIM in 2025
CAISO’s Western Energy Imbalance Market saw an increase in battery storage capacity and coal use in 2025 compared with 2024, although the total load across the market did not increase over the year.
CAISO
EDAM Opening Schedule on Track Despite Lingering Testing Issues
It’s an “all-hands-on-deck” moment for CAISO to open its extended day-ahead market in less than two months, CAISO’s CEO Elliot Mainzer said at a Western Energy Market Board of Governors meeting.
Black Hills Corp.
Black Hills, PowerWatch to Join WEIM in May
Black Hills Energy and PowerWatch are to join CAISO’s Western Energy Imbalance Market, extending the market’s geographical reach into South Dakota, the ISO announced.
Bonneville Power Administration
Nonprofits Tell 9th Circuit BPA’s Day-Ahead Market Decision Poses ‘Imminent’ Harm
The consequences of the Bonneville Power Administration’s decision to join SPP’s Markets+ could hit the Northwest sooner rather than later even though the agency has yet to formally join the market, a group of nonprofits suing it over the choice told the 9th U.S. Circuit Court of Appeals.
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CAISO Unveils Principles for Western Seams Coordination
CAISO released a set of guiding principles for upcoming discussions about seams between the ISO, SPP and other entities as the Extended Day-Ahead Market nears its opening in May.
CAISO
CAISO WEIM Surpasses $8B in Cumulative Benefits
CAISO’s Western Energy Imbalance Market surpassed $8 billion in cumulative economic benefits since its 2014 launch after providing participants with $415.65 million in gross benefits in the fourth quarter of 2025, according to an ISO report.
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EDAM Town Hall Highlights ‘Pivotal Moment for the West’
CAISO leaders staged a virtual “town hall” to stress the importance of a smooth rollout to the ISO’s Extended Day-Ahead Market in May and promise to address market seams issues.

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