U.S. Department of Energy - Energy Efficiency and Renewable Energy
Geothermal Technologies Office
Several geothermal power plants at The Geysers.
Geothermal energy—geo (earth) + thermal (heat)—is heat energy from the earth.
What is a geothermal resource?
Geothermal resources are reservoirs of hot water that exist at varying temperatures and depths below the Earth's surface. Mile-or-more-deep wells can be drilled into underground reservoirs to tap steam and very hot water that can be brought to the surface for use in a variety of applications, including electricity generation, direct use, and heating and cooling. In the United States, most geothermal reservoirs are located in the western states.
Geothermal energy is a vast underutilized heat and power resource that is renewable, baseload, domestic and clean.
Benefits of Geothermal Energy
Renewable—Through proper reservoir management, the rate of energy extraction can be balanced with a reservoir's natural heat recharge rate.
Baseload—Geothermal power plants produce electricity consistently, running 24 hours per day / 7 days per week, regardless of weather conditions.
Domestic—U.S. geothermal resources can be harnessed for power production without importing fuel.
Small Footprint—Geothermal power plants are compact; using less land per GWh (404 mi2) than coal (3642 mi2) wind (1335 mi2) or solar PV with center station (3237 mi2).*
Clean—Modern closed-loop geothermal power plants emit no greenhouse gasses; life cycle GHG emissions (50 g CO2 eq/kWhe) are four times less than solar PV, and six to 20 times lower than natural gas. Geothermal power plants consume less water on average over the lifetime energy output than the most conventional generation technologies.**
*Geothermal Energy Administration. A Guide to Geothermal and the Environment. 2007.
**Argonne National Lab. Life Cycle Analysis Results of Geothermal Systems in Comparison to Other Power Systems; Figure 16, page 43. August 2010.
Argonne National Lab. Water Use in the Development and Operation of Geothermal Power Plants; Table 4-3, page 26. January 2011.