Powering Strong Communities

Public power utilities begin participating in CAISO’s Western Energy Imbalance Market

A number of public power utilities recently began participating in the California Independent System Operator’s (CAISO) Western Energy Imbalance Market (EIM).

The Turlock Irrigation District (TID) and the Balancing Area of Northern California (BANC) Phase 2, comprised of the Modesto Irrigation District (MID), the City of Redding, the City of Roseville, and the Western Area Power Administration (WAPA) Sierra Nevada Region, began participating in the West’s first real-time energy market on March 25.

“Joining the EIM provides MID continued access to the market’s diverse, readily-available power resource mix. Access to this low-cost, growing pool of resources will also further ensure and enhance service reliability to our customers,” Melissa Williams, Public Affairs Manager at MID, told Public Power Current.

“In addition, the EIM offers participants an increased ability to integrate renewable energy needed to meet California’s aggressive environmental goals, provides additional sources of real-time supply to augment reliability resources and, because it’s a voluntary market, allows participants to demonstrate support for regional markets while retaining local control,” she said.

“As participants in the EIM, we have the opportunity to further capitalize on the generation infrastructure TID has developed over the years,” said TID General Manager Michelle Reimers.

TID said its participation in the Western EIM will enable it to economically balance supply and demand within the market area in real-time by scheduling power deliveries every five minutes.

“The Western EIM will provide TID with access to a wider market and allow us to optimize our resources on a more granular scale,” said Dan Severson, TID Assistant General Manager, Power Supply.

“We’re excited that our leadership in the Western EIM successfully demonstrated enough success for our partners to join and expand participation,” said BANC General Manager Jim Shetler in a statement.  “This means greater reliability, lower costs and improved renewable generation for our customers.”

This move affects only WAPA’s Sierra Nevada Region in northern California and Nevada, which operates a sub-balancing authority within BANC.

WAPA is a power marketing administration within the Department of Energy responsible for selling and delivering federal hydropower across high-voltage transmission lines to customers in 15 Midwest and Western states. It is organized in five regions and a management center. 

The Western EIM will help the Sierra Nevada Region “better manage real-time supply and demand on a more frequent basis, harness market efficiencies, improve cost-effectiveness and mitigate the loss of bilateral trading partners in real-time energy transactions,” said Senior Vice President and Sierra Nevada Regional Manager Sonja Anderson.

Having a sub-balancing authority puts “us in a unique position to join the Western EIM; our status required innovative coordination and solutions for market economics, generator dispatch and grid reliability.”

BANC is a Joint Powers Authority consisting of the Sacramento Municipal Utility District (SMUD), MID, Roseville Electric, Redding Electric Utility, Trinity Public Utility District and the City of Shasta Lake as its founding members. SMUD became the first BANC member to join the Western EIM on April 3, 2019.


Meanwhile, the Los Angeles Department of Water and Power (LADWP) and the Public Service Company of New Mexico, an investor-owned utility, began participating in the EIM on April 1.

Participating in the Western EIM will be “a win-win proposition for the City of Los Angeles and the Western grid in terms of fostering the integration of renewable energy while maintaining power reliability, as the City of Los Angeles moves ahead with our goal of 100% renewables as well as assisting all California utilities in meeting the state target of 60% renewables by 2030,” said Reiko Kerr, LADWP Senior Assistant General Manager-Power System Engineering, Planning, and Technical Services, in a statement.

Among other benefits, LADWP said that participating in the Western EIM will help both LADWP and the state address the challenge of maintaining power reliability and reducing greenhouse gas emissions while optimizing the use of renewable energy, such as solar and wind power.

LADWP received approval in 2016 from Los Angeles Mayor Eric Garcetti, the City Council and the Board of Water and Power Commissioners to begin work to join the Western EIM.

LADWP said that the process has involved modifying LADWP’s transmission and generation systems with new grid-level information technology, new systems for billing and tracking energy transactions, improving bulk power metering, and other work to integrate the LADWP system with the CAISO’s other Western EIM participants.

Arizona public power utility Salt River Project and Seattle City Light are also active participants of the Western EIM.

By 2023, 22 active Western EIM participants will represent over 83 percent of the load within the Western Electricity Coordinating Council.