According to Official Guinness Records,
The Geysers geothermal field in the Mayacamas Mountains, California, USA, is the world's biggest single geothermal power base, with 22 geothermal power plants and a total installed capacity of 1,517MW, of which 18 plants and 900MW are currently being utilised. Spread over 117 km², the site has more than 350 steam production wells, some of which are 3 km deep, drilled to tap natural steam that is trapped below in a vast underground reservoir. The steam released is piped overland to a network of interconnected power plants, where it spins turbines which, in turn, run generators to produce electricity – enough to power a city the size of nearby San Francisco. Today, most of the power plants within The Geysers are owned and operated by Calpine, with others run by the US Renewables Group, Northern California Power Agency (NCPA) and Silicon Valley Power.
For a complete list of 2014 records, please visit 2014 Guinness Records in United States.