Exelon Corporation (Exelon) is an energy provider and holding company for several energy businesses. Exelon is engaged in the energy generation business through its Exelon Generation Company, LLC (Generation) subsidiary; wholesale and retail energy sales through its Constellation business unit, and the energy delivery business through its Baltimore Gas and Electric (BGE), Commonwealth Edison Company (ComEd) and PECO Energy Company (PECO) subsidiaries. It operates in 47 states, the District of Columbia and Canada. Exelon Generation has approximately 35,000 megawatts of owned capacity. Constellation provides energy products and services to approximately 100,000 business and public sector customers and approximately 1 million residential customers. Exelon's utilities deliver electricity and natural gas to more than 6.6 million customers in central Maryland, northern Illinois and southeastern Pennsylvania. On March 12, 2012, Constellation Energy Group, Inc. merged into Exelon.