Learn about geothermal energy and if it is a renewable energy source.


Is geothermal energy renewable?

Geothermal energy is a renewable energy source created from the heat generated by the earth's internal core and is available 24-hours a day, 365 days a year. As long as the planet continues to function for millions of years, the core will continue to produce intense amounts of heat that can be utilized to produce electricity.

Many geothermal power plants use a reservoir to store hot water that can be turned into steam to spin turbines to generate electricity. When the water levels in the reservoir begin to deplete, water can be reinjected into the pool to keep the plant running at a high capacity at all times. Aside from routine shutdowns for maintenance, geothermal power plants are available to generate electricity more than 90% of the time during any given year.

Compare that to coal power plants that average around 75% availability in the same year, and you can see that geothermal is renewable, clean and dependable1.

What is the main source of geothermal energy?

Essentially, geothermal energy is heat within the earth. When the heat produced by the earth's core is used to heat water, the interiors of buildings and homes, and generate electricity, it is referred to as geothermal energy. The reason the earth produces heat is because of its liquid iron core. The liquid iron core is so boiling, around 10,800 degrees Fahrenheit to be exact, that it radiates heat through the outer core and the crust of the earth's surface2.

How do geothermal power plants create renewable energy?

There are three main types of geothermal power plants. There is the dry steam, the flash steam, and the binary cycle power plant. All three use the heat that is produced deep within the planet.

Here is a breakdown of the three different main types of geothermal power plants3:

  • Flash steam power plant: The flash steam power plant is the most common and widely used geothermal power plant. Electricity can be produced by taking high-pressure hot water from deep within the earth and converting it to steam to turn generator turbines. Once the steam cools and returns to a liquid form, it is injected back into the land to be used again, making this a form of renewable energy.
  • Dry steam power plant: A dry steam power plant uses steam that naturally rises from underground to turn a turbine generator that generates electricity.
  • Binary cycle power plant: A binary cycle power plant transfers heat from geothermal hot water to another liquid that turns into steam. The steam again is used to drive the generator turbine.

It is also important to note that geothermal power plants that use geothermal water from within the earth require water and steam temperatures between 300 and 700 degrees Fahrenheit. When a source is identified, a well is drilled, and then pipes are inserted to transport the water or steam to the surface, where it is then used to power turbines that generate electricity.

Where is geothermal energy found?

Sources of geothermal energy are almost always naturally occurring, but often they are hard to detect. However, geothermal energy sources can make themselves visible through volcanoes, hot springs, and geysers. These naturally occurring physical phenomena are the primary ways heat escapes from the earth to the surface and into the atmosphere. Most of these geothermal sources exist on or near the boundaries of the earth's tectonic plates.

The most famous plate tectonic boundaries exist around the Pacific plate, deemed the "Ring of Fire." The Ring of Fire consists mainly of mountainous regions that contain a high number of volcanoes. Alaska, Japan, numerous Pacific Islands, New Zealand, and the West Coasts of both North and South America make up most of the perimeter of the Ring of Fire.

Specifically in the United States, most geothermal power plants exist in the western portion of the country and Hawaii. It is in these regions that sources of geothermal energy are closest to the earth's surface. California is the largest producer of geothermal energy4.

What are some uses for geothermal energy?

Geothermal energy has three primary uses when best utilized. They are direct use, like geothermal baths and heat sources for homes and offices, pumps, and electric power generation. Here is a little more detail about these three main uses of geothermal energy5.

  • Direct use: Direct use is when the hot water or steam from a geothermal source is used directly without any specialized equipment, aside from the addition of a heat exchanger. Many pools and showers can use geothermal water for heat. Homes and businesses can use geothermal heat or steam to heat their interiors during cooler temperatures. The use of a heat exchanger helps maximum thermal efficiency and filter other gases and other fumes. Geothermal water and steam can also be used for cooking and for dehydrating fruit or pasteurizing milk.
  • Geothermal heat pump: Geothermal heat pumps are systems used to heat buildings in the winter months and help keep facilities cool during the summer months. Most geothermal heat pumps are combined with a heat exchanger, and they can heat and cool a building using 25% to 50% less electricity than other HVAC systems.
  • Electric power generation: By using geothermal steam, or hot water from the ground that eventually turns into steam, to turn turbines, electricity can be generated when the turbine turns a generator located within a geothermal power plant.

What are geothermal heat pumps?

Geothermal heat pumps are an energy-efficient and cost-effective way to help heat and cool buildings. Whether it is a home or place of business, a geothermal heat pump and heat exchanger can be used to access the consistent subterranean temperatures below the earth's surface. Temperatures 10 feet below the surface consistently hover around 50 to 60-degrees Fahrenheit. Using a geothermal heat pump and heat exchanger, you can access those consistent moderate temperatures to help heat and cool your home6.

Can geothermal energy run out?

Geothermal energy poses no indication that it will be going away anytime soon. The earth has been producing heat from its liquid iron core for millions of years, and it will continue to do so into the future. Combined with the reusing and reinjecting of water into geothermal reservoirs, geothermal energy is a renewable energy source that could be utilized for many generations into the future.

What are the environmental impacts of using geothermal energy?

Geothermal has many promising advantages when it comes to how it affects our environment:

  • There are zero greenhouse gas emissions created during electricity generation through geothermal energy.
  • Water can be reused and reinjected into geothermal reservoirs, continuously saving on water resources.
  • If a geothermal plant does produce solid waste, it usually comes in the form of sludge-like material that contains high concentrations of zinc, silica, and sulfur that can be extracted, sold, and/or used in the production of other materials and products.

Is geothermal a reliable source of renewable energy?

Geothermal energy is highly reliable, especially when you compare it to coal and other nonrenewable energy sources. Geothermal energy is available all year round, and geothermal power plants average availability is above 90%. Coal power plants are only available for electricity generation, on average, around 75% of the time. As a reliable energy source, geothermal energy is an excellent opportunity to prove renewable energy can improve the environmentally harmful tendencies of the energy industry.

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  1. energy.gov/eere/geothermal/geothermal-faqs 

  2. eia.gov/energyexplained/geothermal 

  3. eia.gov/energyexplained/geothermal/geothermal-power-plants.php 

  4. eia.gov/energyexplained/geothermal/where-geothermal-energy-is-found.php 

  5. britannica.com/science/geothermal-energy/Environmental-effects-and-economic-costs 

  6. eia.gov/energyexplained/geothermal/geothermal-heat-pumps.php