Environmental Integrity

Geothermal Energy

The Basics

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TITLE: Geothermal Energy - The Basics

AUTHOR: Office of Energy Efficiency and Renewable Energy

SOURCE: Office of Eenergy Efficiency and Renewable Energy, U.S. Department of Energy

COPYRIGHT: No protection is claimed in original U.S. Government works.

Geothermal energy is heat energy from the earth—Geo (earth) + thermal (heat).

Geothermal resources are reservoirs of hot water that exist or are human made at varying temperatures and depths below the Earth's surface. Wells, ranging from a few feet to several miles deep, 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 in the western states.


Renewable—The heat flowing from Earth’s interior is continually replenished by the decay of naturally occurring radioactive elements and will remain available for billions of years.

Baseload—Geothermal power plants produce electricity consistently and can run essentially 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. They use less land per gigawatt-hour (404 m2) than comparable-capacity coal (3,642 m2), wind (1,335 m2), and solar photovoltaic (PV) power stations (3,237 m2)*.

Clean—Modern closed-loop geothermal power plants emit no greenhouse gasses and have life cycle emissions four times lower 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 most conventional electricity-generation technologies**.


The 2019 GeoVision analysis indicates potential for up to 60 gigawatts of electricity-generating capacity, more than 17,000 district heating systems, and up to 28 million geothermal heat pumps by 2050. If we realize those maximum projections across sectors, it would be the emissions reduction equivalent of taking 26 million cars off U.S. roads every year.

*Geothermal Energy Administration. A Guide to Geothermal and the Environment. 2007.

**Argonne National Laboratory. Life Cycle Analysis Results of Geothermal Systems in Comparison to Other Power