Learn about geothermal energy, heat from inside the Earth. A simple guide to how geothermal power works, its pros and cons, and fun facts.
Deep beneath your feet, the Earth is hot. Really hot. The temperature at the Earth’s core is about the same as the surface of the sun. This heat is called geothermal energy. The word comes from Greek. Geo means earth. Thermal means heat. People have used geothermal energy for thousands of years. Ancient Romans bathed in naturally hot springs. Today, we use it to generate electricity and heat buildings. It is clean, renewable, and always available.
Geothermal energy is heat from inside the Earth. The Earth has several layers. The outer layer is the crust. Below that is the mantle. The mantle contains hot liquid rock called magma. At the center is the core. The core is extremely hot.
Heat flows from the core toward the surface. Most of the time, this heat stays deep underground. But in some places, it comes closer to the surface. This happens near volcanoes, hot springs, and geysers. In these places, we can capture the heat and use it.
The heat inside the Earth comes from two sources. First, there is leftover heat from when the Earth formed billions of years ago. Second, radioactive elements like uranium and thorium decay naturally inside the Earth. This decay produces heat. Both sources are constant. That is why geothermal energy is renewable.
Geothermal power plants use heat from the Earth to make electricity. Here is how it works.
First, engineers drill wells deep into the ground. Some wells go down 10,000 feet or more. They reach underground reservoirs of hot water or steam.
The hot water or steam rises through the wells to the surface. The steam is piped to a turbine. The high-pressure steam spins the turbine blades. The spinning turbine turns a generator. The generator produces electricity.
After the steam spins the turbine, it cools back into water. The water is injected back into the ground through another well. This recharges the underground reservoir. The same water can be used again and again.
There are three main types of geothermal power plants.
Dry steam plants. These use steam directly from underground. The steam goes straight to the turbine. This is the oldest type of geothermal plant.
Flash steam plants. These use hot water from underground. The water is under high pressure. When it rises to the surface, the pressure drops. The water flashes into steam. The steam spins the turbine.
Binary cycle plants. These use moderately hot water. The water heats a second liquid that has a lower boiling point. The second liquid turns to vapor and spins the turbine. This type works with lower temperatures.
Geothermal energy is not just for electricity. It can also heat buildings directly. This is called district heating. Hot water from underground is piped to buildings. The buildings use the heat for warmth and hot water.
Iceland is famous for this. The capital city Reykjavik uses geothermal energy to heat most of its buildings. Even the sidewalks are heated in winter. This keeps them free of ice and snow.
Geothermal heat pumps are another option. These use the constant temperature of the shallow ground. Just 10 feet below the surface, the ground stays at about 55 degrees Fahrenheit year round. A heat pump uses this stable temperature to heat buildings in winter and cool them in summer.
Did you know the ground under your feet is warm? If you dig deep enough, it gets very hot. So hot that it can boil water. This heat is called geothermal energy.
Long ago, people found hot springs. They would sit in the warm water and relax. Today, we use the heat to make electricity.
Here is how it works. Imagine a pot of water on a stove. The water gets hot and turns into steam. The steam pushes up. In a geothermal plant, the Earth is the stove. It heats water underground. The steam comes up through pipes and spins a big fan. The spinning fan makes electricity.
Geothermal energy is special because it never runs out. The Earth will stay hot for billions of years. It is also very clean. It does not make any smoke.
Geothermal energy has some limits. It can only be used in places where hot water or steam is close to the surface. These places are usually near tectonic plate boundaries. The Ring of Fire around the Pacific Ocean has many geothermal sites.
The United States is the world’s largest producer of geothermal electricity. Most US geothermal plants are in California. The Geysers in northern California is the largest geothermal field in the world.
Iceland is a geothermal success story. The country sits on a volcanic hotspot. It uses geothermal energy to heat almost all its buildings. About 25 percent of its electricity comes from geothermal.
New technology is expanding geothermal energy. Enhanced geothermal systems or EGS can create reservoirs in hot rock where no natural water exists. Engineers inject water into the hot rock and then extract the heated water. This could make geothermal energy available in many more places.
Myth: Geothermal energy is only available in volcanic areas. Traditional geothermal needs hot rock near the surface. But new enhanced geothermal systems could work in many more places.
Myth: Geothermal energy is expensive. Geothermal plants have high upfront costs. But they have very low operating costs. Over time, geothermal is very competitive.
Myth: Geothermal energy is not widely used. Geothermal provides electricity in over 20 countries. It heats buildings in many more. Its use is growing.
Last updated: June 15, 2026
What does the word geothermal mean?
What is used to turn the turbine in a geothermal plant?
Is geothermal energy renewable?
Which country gets about 25 percent of its electricity from geothermal?
What creates the heat inside the Earth?
Answers: B: Earth heat, B: Steam from underground, A: Yes, B: Iceland, B: Decay of radioactive elements
What is geothermal energy?
Geothermal energy is heat that comes from inside the Earth. The word geothermal comes from Greek words. Geo means earth. Thermal means heat. This heat can be used to generate electricity and heat buildings.
How does geothermal energy work?
Wells are drilled deep into the ground to reach hot water or steam. The steam rises to the surface and spins a turbine. The turbine turns a generator that makes electricity.
Is geothermal energy renewable?
Yes. Geothermal energy is renewable. The Earth's interior heat is constantly produced by the decay of radioactive elements. It will not run out for billions of years.
Where is geothermal energy used?
Geothermal energy is used in many countries. Iceland gets about 25 percent of its electricity from geothermal. The United States is the largest producer of geothermal electricity in the world.
What are the advantages of geothermal energy?
Geothermal energy is clean, reliable, and renewable. It produces almost no emissions. It runs 24/7 regardless of weather. It takes up very little land compared to solar or wind.
