Geothermal energy is simply the heat from beneath the earth’s surface. About ten feet below the earth’s surface, the temperature is a constant 50-60 degrees Fahrenheit. Unlike wind and solar, geothermal’s power source never varies, which means its efficiency is always 100%.

A heat pump, which is the basis for this technology, has two units: a condenser (outdoors) and an evaporator (indoors). A closed loop carries a liquid, called refrigerant, carries heat from one area to another. In the winter, geothermal energy can help you warm your house because the temperature underground is higher than the air temperature. In the summer, geothermal energy can help cool your house, because the ground temperature is lower than the air temperature. The geothermal system exchanges the warmer air for the cooler air and delivers a comfortable temperature where you need it.