Although geothermal heat pumps can be used almost anywhere, most direct-use and electrical production facilities in the United States are located in the west, where the geothermal resource base is concentrated.
Current drilling technology limits the development of geothermal resources to relatively shallow water- or steam-filled reservoirs, most of which are found in the western part of the United States. But researchers are developing new technologies for capturing the heat in deeper, "dry" rocks, which would support drilling almost anywhere.
Conventional hydrothermal resources make up most of the current geothermal operating plants in the United States. Power generation comes from drawing heat from the fluid found naturally deep below the Earth's surface. Steam is captured at the surface and spins a turbine, which then powers an electric generator