Look Down for Heat

Posted by E.B. Boyd on March 18, 2009 - 1:39pm.

Sure, you've thought about adding solar panels to your roof as a way of reducing your home's carbon footprint. Maybe you've even given wind a gander. How about a ground source heat pump?

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% more efficient than conventional (read: fossil fuel-based) heating and cooling systems. Yes, they're expensive to install. But most break even within five to ten years--a good deal when you consider that they tend to last 25 years (for the pump -- 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. A heat pump lays tubes into the ground outside your home and then circulates water through it to capture the heat there, bring it into your home, and pump it up (through a heat exchanger) to bring it to the comfortable 72 degrees you enjoy during the winter. 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:

(Source: newgroundwork)

How much they cost

According to the Department of Energy, GSHPs cost about $7,500 for a typical home (not including labor) compared to $4000 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

Pro: GSHPs can be installed anywhere. They're 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 the bonus is that they use 30-60% less energy than a conventional HVAC system.

For More:

• Department of Energy's Consumer Guide to ground source heat pumps
• Frequently Asked Questions from the International Ground Source Heat Pump Association

Image courtesy of extreme-nation.