Geothermal energy is contained in underground reservoirs of steam, hot water, and hot dry rocks. Geothermal power is cost effective, reliable, environmentally friendly, and sustainable. Recent advances in technology have expanded the size and range of geothermal power applications. At electric generating facilities, hot water or steam is drawn from geothermal reservoirs in the Earth's crust and is supplied to steam turbines at electric utilities that drive generators to produce electricity. Moderate-to-low termperature geothermal resources are used for direct-use applications such as district and space heating. Lower temperature, shallow ground, geothermal resources are used by geothermal heat pumps to heat and cool buildings.