About

The ISO’s Western Energy Imbalance Market (WEIM) is a real-time energy market, the first of its kind in the western United States.

The WEIM’s advanced market system automatically finds low-cost energy to serve real-time consumer demand across the west. Since its launch in 2014, the WEIM has enhanced grid reliability and generated cost savings for its participants. Besides its economic advantages, the WEIM improves the integration of renewable energy, which leads to a cleaner, greener grid.


Participants

BHE Montana – entry 2026

Avangrid – entered 2023

El Paso Electric – entered 2023

WAPA Desert Southwest Region – entered 2023

Bonneville Power Administration – entered 2022

Tucson Electric Power – entered 2022

Avista – entered 2022

Tacoma Power – entered 2022

NorthWestern Energy – entered 2021

Los Angeles Department of Water & Power – entered 2021

Public Service Company of New Mexico – entered 2021

Turlock Irrigation District – entered 2021

Salt River Project – entered 2020

Seattle City Light – entered 2020

Balancing Authority of Northern California – entered 2019

Idaho Power Company – entered 2018

Powerex – entered 2018

Portland General Electric – entered 2017

Puget Sound – entered 2016

Arizona Public Service – entered 2016

NV Energy – entered 2015

PacifiCorp – entered 2014

California ISO – entered 2014


Implementation documents

  • Avista
  • Arizona Public Service
  • Avangrid Renewables LLC
  • Balancing Authority of Northern California
  • Bonneville Power Administration
  • El Paso Electric Company
  • Idaho Power Company
  • Los Angeles Department of Water and Power
  • NorthWestern Energy
  • NV Energy
  • PacifiCorp
  • Public Service Company of New Mexico
  • Puget Sound Energy
  • Portland General Electric
  • Powerex Corp
  • Salt River Project
  • Seattle City Light
  • Tacoma Power
  • Tucson Electric Power
  • Western Area Power Administration
  • Turlock Irrigation District

Active participants

Download map

See the latest quarterly benefits report.