PJM Interconnection

PJM Interconnection LLC (PJM) is a regional transmission organization (RTO) in the United States. It is part of the Eastern Interconnection grid operating an electric transmission system serving all or parts of Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and the District of Columbia.

PJM, headquartered in Valley Forge, Pennsylvania, was the world's largest competitive wholesale electricity market until the development of the European Integrated Energy Market in the years 2000s. More than 900 companies are members of PJM, which serves 61 million customers and has 183.6 gigawatts of generating capacity. With 1,376 generation sources, 62,556 miles (100,670 km) of transmission lines and 6,038 transmission substations, PJM delivered 791 terawatt-hours of electricity in 2013.

Started in 1927, the pool was renamed the Pennsylvania-New Jersey-Maryland Interconnection (PJM) in 1956. The organization continues to integrate additional utility transmission systems into its operations.

In 1927 the Public Service Electric and Gas Company, Philadelphia Electric Company, and Pennsylvania Power & Light Company formed a power pool called the Pennsylvania-New Jersey Interconnection. The purpose of the power pool was to dispatch electric generating plants on a lowest cost basis, thereby reducing the electric costs for all members of the pool.

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