CMS Energy Corporation, through its subsidiaries, operates as an energy company primarily in Michigan. The company operates in three segments: Electric Utility, Gas Utility, and Enterprises. The Electric Utility segment involves in the generation, purchase, distribution, and sale of electricity to residential, commercial, and diversified industrial customers in Michigan's Lower Peninsula. It operates a network of coal, gas, hydroelectric, oil, and wind generation plants. This segment's distribution system includes 421 miles of high-voltage distribution radial lines; 4,259 miles of high-voltage distribution overhead lines; 17 miles of high-voltage distribution underground lines; 55,965 miles of electric distribution overhead lines; 10,162 miles of underground distribution lines; and substations with an aggregate transformer capacity of 24 million thousand volt-amperes. The Gas Utility segment engages in the purchase, transmission, storage, distribution, and sale of natural gas. This segment's gas distribution and transmission consists of 26,720 miles of distribution mains; 1,657 miles of transmission lines; 7 compressor stations with a total of 151,172 installed and available horsepower; and 15 gas storage fields with an aggregate storage capacity of 309 billion cubic feet of gas and a working storage capacity of 143 billion cubic feet of gas. The Enterprises segment is involved in the independent power production and marketing activities. As of December 31, 2012, it had ownership interests in independent power plants fueled by natural gas, coal, and biomass totaling 1,135 gross megawatts. CMS Energy Corporation was founded in 1987 and is based in Jackson, Michigan.