SOURCE: California Independent System Operator Corporation

California Independent System Operator Corporation

October 03, 2016 12:52 ET

Arizona Public Service, Puget Sound Energy Enter the EIM

ISO Real-Time Market Is Now Providing Low-Cost Energy to Consumers in Eight Western States

FOLSOM, CA--(Marketwired - October 03, 2016) - After months of intensive testing, Phoenix-based Arizona Public Service (APS) and Puget Sound Energy (PSE) of Washington state successfully began full participation in the western Energy Imbalance Market (EIM) on Saturday, October 1.

The real-time wholesale power market managed by the California Independent System Operator (ISO) enables participating utilities to buy low cost energy available across eight western states. APS and PSE join NV Energy, which serves 90 percent of Nevada, and PacifiCorp, which has customers in six states, as part of the Energy Imbalance Market.

"Participation by Arizona Public Service and Puget Sound Energy in the EIM 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, ISO President and CEO. "I want to thank the utilities for their hard and collaborative work in preparing for the EIM and appreciate their commitment to the market's success."

The EIM uses ISO's state-of-the-art software to automatically analyze western grid needs and find the lowest-cost generation to meet demand every five minutes. Participating utilities also can access low-cost renewable energy in other western states in real time to offset power generated from local energy plants. From January to June this year, greenhouse gas emissions were reduced by an estimated 292,000 metric tons because of EIM participation. This is equivalent to the emissions otherwise generated to power nearly 31,000 homes for one year*.

Since launching in November 2014, the Energy Imbalance Market has produced benefits of more than $88 million dollars by effectively using the low cost energy available in the region to meet changes in real-time energy demand. Those savings are projected to increase as more utilities join the EIM.

With the addition of Arizona Public Service, the EIM expands into the Grand Canyon State, where the utility serves 1.2 million customers in 11 of the state's 15 counties. Independent studies found that APS customers could save $7 million to $18 million a year through EIM participation, while Puget Sound Energy's 1.1 million customers could save $18 million to $30 million. As well as Arizona, the EIM is serving over 5 million consumers in California, Washington, Oregon, Idaho, Wyoming, Nevada and Utah.

Future EIM participants include Portland General Electric, which is scheduled to enter the market in October 2017, and Idaho Power, which plans to enter the market in April 2018.

For more information on EIM, visit the ISO's EIM webpage here.


The California ISO provides open and non-discriminatory access to one of the largest power grids in the world. The vast network of high-voltage transmission power lines is supported by a competitive energy market and comprehensive grid planning. Partnering with about a hundred clients, the nonprofit public benefit corporation is dedicated to the continual development and reliable operation of a modern grid that operates for the benefit of consumers. Recognizing the importance of the global climate challenge, the ISO is at the forefront of integrating renewable power and advanced technologies that will help meet a sustainable energy future efficiently and cleanly.

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