Geo" means "from the earth," and "thermal" means "heat," so this type of energy is found under the earth. The hot lava from a volcano and the hot steam from a geyser both come from underground heat and we can use that same type of heat in our homes.
Here's how it works: about four feet underground, the temperature of the earth stays the same all year long, about 55 degrees.
A geothermal heating system uses pipes buried more than four feet deep in the earth. That is another reason why it's important for adults to call 811 before they dig in their yard so they don't hit buried piping.
The system pumps a liquid through the pipes to absorb the heat and brings it back indoors. A device called a "heat exchanger" takes the heat from the liquid and uses it to heat the air inside the home.
A geothermal system can cool your house during the summer, too! It just works in reverse, absorbing the heat from the air inside your home and moves it back into the earth.
A geothermal heater is also very energy-efficient. Almost none of the energy used is wasted, so it helps keep heating bills very low during the winter.