Powering Strong Communities

BPA Joins CAISO’s Western Energy Imbalance Market

The Bonneville Power Administration (BPA) is one of the newest members of the California Independent System Operator’s (CAISO) Western Energy Imbalance Market (WEIM).

“Joining the Western EIM is a monumental and meaningful step in the modernization of our operations that unlocks a range of benefits for Bonneville and our customers,” John Hairston, BPA administrator and CEO, said in a statement.

BPA is a nonprofit federal power marketer that sells hydropower from 31 federal dams in the Columbia River Basin, as well as power from the region’s only nuclear plant. BPA delivers nearly one a third of the power generated in the Northwest to more than 140 electric utilities.

BPA was joined in its May 3 entry into WEIM by Tucson Electric Power (TEP), which provides electric service to more than 438,000 customers in southern Arizona.

“The Federal Columbia River Power System is a vital source of clean energy that will bring significant resource diversity and transmission capability to the WEIM,” Elliot Mainzer, president and CEO of CAISO, said in a statement. “And with the participation of Tucson Electric Power, we have another highly valued partner in the Desert Southwest.”

The WEIM uses its technology to find and deliver the lowest-cost energy to members across a broad, multi-state region. With the addition of the new members, the WEIM will be better able to provide increased reliability and environmental gains through the real-time transfer of energy, CAISO said.

CAISO has operated the WEIM since late 2014 and now has 19 participants serving 77 percent of electric demand in the Western United States. In March, Tacoma Public Utilities and Avista Utilities joined the WEIM.

Building on the growth of the Western Energy Imbalance Market, CAISO has been working with WEIM members to develop an Extended Day-Ahead Market (EDAM).

On April 28, CAISO released its EDAM straw proposal. The straw proposal seeks to establish the framework for key design elements of the day-ahead market, as well as areas requiring additional work and stakeholder input.

Current plans call for implementation testing in 2023 and onboarding the first set of EDAM participants in early 2024.