Which are better for the environment, geothermal heating systems or geothermal cooling systems?

Earth brims with a limitless source of geothermal energy.
Earth brims with a limitless source of geothermal energy.

In 2009, residents of Mount Airy, Md., might have noticed some strange goings on in the backyard of Mike Dixon's South Main Street home. Dixon was drilling holes. One over here, another over there. Dixon wasn't looking for buried treasure. He wasn't drilling for water.

Instead, Dixon was drilling the holes to install a geothermal heating and cooling system [source: Cochrun].

Dixon dug two holes 450 feet (137.16 meters) deep. When he finished, Dixon installed polyethylene pipes in the ground. He connected those pipes to a special unit that could heat his house in the winter and cool it in the summer. The source of all this power is Earth itself [source: Cochrun].

Earth brims with a limitless source of energy. It's called geothermal from the Greek words geo, or "earth," and therme, or "heat."

Deep inside the planet is a lot of hot water and steam -- the deeper you go, the hotter it gets. In fact Earth's core is so hot that it can melt rock, which is known as magma. Some magma escapes through cracks in Earth's crust. However, most magma stays beneath the surface, heating pools of water. Most of that hot water sits below ground in geothermal reservoirs. Sometimes that hot water comes to the surface and pools in hot springs, or erupts as geysers.

People have known the benefits of geothermal energy for centuries. The ancient Romans used hot springs to heat homes. In 1892, Boise, Idaho began using water from a nearby hot spring to heat some of that city's buildings. Today, Boise has the largest geothermal direct-use system in the United States, providing heat to more than 55 downtown businesses [source: City of Boise].

Unlike oil and other fossil fuels, geothermal energy is renewable. It's clean, abundant, and once you make the initial investment of setting up a system -- it's cheap. Dixon says his geothermal system cost nearly $40,000 to install. But in Dixon's view, the government tax breaks and the prospect of lower energy bills made geothermal energy a no-brainer [source: Cochrun].

Are geothermal heating and cooling systems really better for the environment? Which system uses less energy and can save you money? Click to the next page to find out.