As of March 12, 2012, Constellation Energy Group, Inc. was acquired by Exelon Corporation. Constellation Energy Group, Inc., an energy company, develops, owns, operates, and maintains fossil and renewable generating facilities in the United States and Canada. As of December 31, 2011, the company had interests in generating facilities totaling 11,751 megawatts (MW) of generating capacity. It also manages approximately 1,100 MW associated with long-dated tolling agreements; and provides operation and maintenance services, including testing and start-up to owners of electric generating facilities. The company supplies electricity, natural gas, and other energy products and services to wholesale and retail electric and natural gas customers. In addition, it manages generation facilities and natural gas properties; provides risk management services; trades in energy and energy-related commodities; engages in the upstream natural gas activities; and designs, constructs, and operates renewable energy, heating, cooling, and cogeneration facilities. Further, the company offers home improvements; sells electric and gas appliances; and services heating, air conditioning, plumbing, electrical, and indoor air quality systems. Additionally, it purchases, transmits, distributes, and sells electricity, as well as purchases, transports, and sells natural gas in central Maryland. The company maintains approximately 240 substations and approximately 1,300 circuit miles of transmission lines, and approximately 24,800 circuit miles of distribution lines. The company was formerly known as Constellation Energy Corporation and changed its name to Constellation Energy Group, Inc. in 1995. Constellation Energy Group, Inc. was founded in 1995 and is based in Baltimore, Maryland.