How it works

The Western Energy Imbalance Market (WEIM) allows participants to buy and sell power close to the time electricity is consumed, and gives system operators real-time visibility across neighboring grids. The result improves balancing supply and demand at a lower cost.

The WEIM platform balances fluctuations in supply and demand by automatically finding lower-cost resources to meet real-time power needs. The WEIM manages congestion on transmission lines to maintain grid reliability and supports integrating renewable resources. In addition, the market makes excess renewable energy available to participating utilities at low cost rather than turning the generating units off.

More specifically, regional coordination in generating and delivering energy produces significant benefits in three main areas:

  • Reduced costs for participants by lowering the amount of costly reserves utilities need to carry, and more efficient use of the regional transmission system.
  • Reduced carbon emission and more efficient use and integration of renewable energy. For instance, when one utility area has excess hydroelectric, solar or wind power, the ISO can deliver it to customers in California or to another participant. Likewise, when the ISO has excess solar energy, it can help meet demand outside of California that otherwise would be met by more expensive – and less clean – energy resources.
  • Enhanced reliability by increasing operational visibility across electricity grids, and improving the ability to manage transmission line congestion across the region’s high-voltage transmission system.

The WEIM is managed by a five member Governing Body.