Calpine Corporation, a wholesale power generation company, owns and operates natural gas-fired and geothermal power plants in North America. It operates natural gas-fired combustion turbines and renewable geothermal conventional steam turbines. The company sells power, steam, capacity, renewable energy credits, and ancillary services to utilities, independent electric system operators, industrial and agricultural companies, retail power providers, municipalities and other governmental entities, and power marketers, as well as retail commercial, industrial, and residential customers.