OK, here’s the deal. Ground source heat pumps (GSHPs) — sometimes called “geothermal” or “geoexchange” systems — essentially use the ground outside or under your home to bring heat inside in the winter and take heat out in the summer. These systems are about 400 percent more efficient than conventional (read: fossil fuel-based) heating and cooling systems. Yes, they’re expensive to install. But with most, you’ll break even within five to 10 years — a good deal when you consider that most pumps tend to last 25 years (the loops installed in the ground can last 50 years or more). About 50,000 families and businesses install GSHPs every year.
How they work
About five feet underground, the earth’s temperature remains consistent all year-round — about 50-70 degrees Fahrenheit, depending on where you live. With a geothermal system, water circulates through tubes run into the ground outside your home. In the winter, the temperature of the ground heats the water, then the tubes pump the water back up and through a heat exchanger to bring the air in your home to a warm, comfortable temperature. In the summer, this process is reversed. Heat in your home gets sucked down into the tubes and sent out into the ground, leaving your home nice and cool.
This simple video does a great job of explaining the basic principles involved:
How much they cost
According to the Department of Energy, GSHPs cost about $7,500 for a typical home (not including labor) compared to $4,000 for a traditional heating/cooling system (also not including labor). If you decide to go this direction, however, remember to check for federal, state, and local energy efficiency rebates. Start here: Dsireusa.org.
How they compare to solar and wind
Here’s how geothermal stacks up against other green energy options:
Pro: GSHPs can be installed anywhere and are not dependent on the supply of a natural resource, like sun or wind.
Con: GSHPs are not completely energy independent. You still need to use electricity from the grid to run the system. But they do use 30-60 percent less energy than a conventional HVAC system.
- Department of Energy’s Consumer Guide to ground source heat pumps
- Frequently Asked Questions from the International Ground Source Heat Pump Association
Learn more about green energy with sustainability videos on GaiamTV.com.
Photo: U.S. Department of Energy