Two Entities Join WEIM

Market Expands Into 12 Western States

Two new entities joined the Western Energy Imbalance Market (WEIM) on May 6, 2026 adding resources that generate and store renewable power, diversify generation, enhance reliability, and support cost savings across 12 western states.

One of the many considerations to adding resources to WEIM is ensuring consistent methods to meter transactions and provide accurate data for financial settlements.

Trimark’s expert in California ISO (CAISO) markets and metering explains. “There are numerous requirements to make WEIM a reality,” said Glen Perez, Trimark’s Senior Director of Consulting Services. “We worked with PowerWatch to guide them through the strict rules around meter data validation and submission that support accurate settlements in this multi-billion dollar market. The Scheduling Coordinator Metering Entity (SCME) approach allows the market to expand while ensuring accurate data about electric power transactions.”

Trimark worked closely with the PowerWatch team (and their consultant Utilicast) to create Settlement Quality Meter Data (SQMD) Plans describing metering and data processing for PowerWatch’s portfolio.

Mr. Perez is a 20-year veteran of CAISO. While there, he participated in defining WEIM, SCME, metering rules, and more to support the Tariff. Today, Glen helps resource owners, like PowerWatch, make informed decisions regarding New Resource Implementation (NRI), SQMD, and complex revenue metering. This unique set of experience is an advantage to entities seeking to join WEIM in the future.

“The Western Energy Imbalance Market (WEIM) continues to grow,” states the California ISO (CAISO) in their Energy Matters blog. “The real-time market, which has delivered more than $8 billion in economic benefits to its members and their customers since 2014, will soon have two new participants and a new state to operate in. The WEIM, which helps utilities efficiently buy and sell least-cost power close to the time it is used, will be joined in May by Black Hills Energy and PowerWatch (formerly BHE Montana).”

Trimark worked closely with the PowerWatch team (and their consultant Utilicast) to create Settlement Quality Meter Data (SQMD) Plans describing the metering and data processing for PowerWatch’s portfolio. That portfolio includes 567 MW of wind, solar and battery resources. Trimark also helped PowerWatch develop SCME Plans and process SQMD for the interties that connect the PowerWatch grid with other ISOs.

To help them prepare for the change, Trimark guided PowerWatch through SQMD Planning then instituted automated meter reading and meter data management processes. During market simulation and parallel operations, Trimark read revenue meters for the PowerWatch resources and interties and submitted meter data required for operational and settlement testing.

Trimark will continue to support PowerWatch with daily meter reading, Meter Data Management services (MDM) and SQMD submittals as required for market settlements. But the job doesn’t end there. In accordance with their approved SQMD Plan, Trimark will also help PowerWatch conduct their Annual Affirmation and a bi-annual Self Audit of processes as evidence of ongoing compliance.

Background on WEIM

In 2014, the CAISO lead the creation of the Energy Imbalance Market (EIM); expanding voluntary power management to Balancing Authorities Areas (BAAs) that wish to cooperate in the Real-Time Imbalance Market. The market was subsequently renamed the Western Energy Imbalance Market (WEIM).

Most of the meter data used to settle WEIM transactions is submitted by an SCME. Operating as an SCME provides flexibility in the owner’s approach to metering. Advantages include:

• Flexibility in meter selection and testing.
• Ability to implement advanced, peer-to-peer metering schemes and Dynamic Loss Compensation as required to meter actual energy losses.
• Early detection and resolution of meter or communication issues. Trimark reads meters every business day.
• Owners and the Scheduling Coordinator review SQMD data before submitting data for settlement.
• Flexibility in the areas of operation, maintenance and market settlement for resource owners.

Trimark’s Services

Trimark works with resource owners to develop and submit SQMD Plans then conduct Annual Affirmations and bi-annual Self Audits. Trimark also reads meter data every business day via MV-90 then applies industry-standard Validation, Estimation, and Editing (VEE) protocols to prepare SQMD to fulfill settlement and compliance requirements.