Evolution of the WEIM

By ISO Staff |


At the ISO’s August 30 forum on an Extended-Day Ahead Market, Elliot Mainzer, the California Independent System Operator’s president and CEO, made a brief presentation in his closing remarks illustrating the evolution of the ISO’s Western Energy Imbalance Market (WEIM) since its launch in 2014.

Starting with just the ISO and PacifiCorp, the WEIM has grown to 22 entities in 11 states and serves 80 percent of the electricity load in the Western U.S. It has also generated more than $4 billion in benefits for market participants while further diversifying energy resources, improving transmission efficiencies and reducing greenhouse gas emissions.

Seeking to build on and expand that success by establishing an extended day-ahead market, the ISO has filed proposed tariff changes for the broader day-ahead market with the Federal Energy Regulatory Commission, requesting a FERC ruling by December 21, 2023.

As Mainzer told the forum’s audience while sharing a slide of the WEIM’s current footprint and connectivity, "This is what we’ve built together as a Western energy community. And this map, and this transmission connectivity and this resource diversity is really the physics that underlies both the economic and the reliability benefits that we’ve seen through the Western Energy Imbalance Market."

"And it is, of course, the reason why our central proposition now is to build on this platform and to take that next really important evolutionary step into the day ahead market."

You can listen to the short video and see the slides tracing WEIM’s evolution and the expected benefits for California and the West from expanding into the day-ahead timeframe on the ISO’s YouTube channel.

Back to top