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 is the largest power grid operator in the United States, serving 67 million customers from Chicago to New Jersey.

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 2000s. More than 1,000 companies are members of PJM, which has 182 gigawatts of generating capacity. With 1,436 electric power generators and 88,333 miles (142,158 km) of transmission lines, PJM delivered over 800 terawatt-hours of electricity in 2024.

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. The Federal Energy Regulatory Commission (FERC) regulates PJM, and approves its open access transmission tariff for the wholesale electricity market.

In 2026, PJM is anticipating future supply shortages due to expected 5% annual demand growth (compared to no growth from 2005-2020) from new data centers, combined with supply constraints from shutdowns of many generation plants for environmental or economic reasons, and the difficulty of timely permitting of new power plants.