Geothermal Energy Basics

Geothermal energy is the heat from the earth. This heat is used for bathing, to heat buildings, and to generate electricity.

The word geothermal comes from the Greek words geo (earth) and therme (heat), and geothermal energy is a renewable energy source because heat is continuously produced inside the earth. Many technologies have been developed to take advantage of geothermal energy:

  • Hot water or steam reservoirs deep in the earth that are accessed by drilling
  • Geothermal reservoirs located near the earth's surface, mostly located in the western U.S., Alaska, and Hawaii
  • The shallow ground near the Earth's surface that maintains a relatively constant temperature of 50-60°F.

This variety of geothermal resources allows them to be used on both large and small scales. A utility can use the hot water and steam from reservoirs to drive generators and produce electricity for its customers. Other applications apply the heat produced from geothermal directly to various uses in buildings, roads, agriculture, and industrial plants. Still others use the heat directly from the ground to provide heating and cooling in homes and other buildings. Learn more about NREL's geothermal research.

Geothermal Applications

Heat Pumps

Heat pumps use the Earth's shallow ground temperature for heating and cooling. Learn more about heat pumps.

Electricity Production

Electricity production generates electricity from the earth's heat. Learn more about electricity production.

Direct Use

Direct use produces heat directly from hot water within the earth.

Additional Resources

For more information about geothermal technologies, visit the following resources:

Geothermal Technologies Program
U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy

Energy Kids Geothermal Basics
U.S. Energy Information Administration Energy Kids