Calpine Corporation is a power generation company. The Company is engaged in the ownership and operation of primarily natural gas-fired and geothermal power plants in North America. The Company's segments include West (including geothermal), Texas and East (including Canada). In the Northeast and Mid-Atlantic regions, the Company has generating units capable of burning either natural gas or fuel oil. The Company operates its business through various divisions and subsidiaries. The Company's portfolio consists of various types of power generation technologies, including natural gas-fired combustion turbines, which include combined-cycle plants and renewable geothermal conventional steam turbines. Its Geysers Assets located in northern California represent the geothermal power generation portfolio in the United States, as well as the producing power generation asset of all renewable energy in the state of California.