Phoenix-based Arizona Public Service (APS) and Puget Sound Energy (PSE) of Washington State began full participation in the western Energy Imbalance Market (EIM) on October 1.

The EIM is a real-time wholesale power market managed by the California Independent System Operator (ISO) that enables participating utilities to buy low-cost energy available across eight western states.

The two utilities join NV Energy, which serves 90% of Nevada, and PacifiCorp, which has customers in six states, as part of the Energy Imbalance Market.

Participation in the EIM by the Arizona and Washington utilities “will strengthen the market and yield substantial benefits in the form of access to low cost energy for them and for all EIM participants,” said Steve Berberich, President and CEO of the California ISO.

The EIM monitors power needs on the western grid needs and every five minutes finds the lowest-cost generation to meet demand.

Participating utilities also can access low-cost renewable energy. From January to June this year, EIM participation reduced greenhouse gas emissions by an estimated 292,000 metric tons, the equivalent of emissions generated by fossil fuel plans to power about 31,000 homes for a year.

Since launching in November 2014, the Energy Imbalance Market has savings of more than $88 million dollars by effectively using low-cost energy available in the region to meet changes in real-time demand.

Arizona Public Service customers are projected to save $7 million to $18 million a year through EIM participation, while Puget Sound Energy’s customers could save $18 million to $30 million.