When you look at the most common type of air conditioning system used in homes, you see a conspicuous part of it outside. That’s the condenser. Its job is to take the heat delivered to it from inside the house, and vent it off into the atmosphere.

Depending on its location, it often sits in the bright sun, using plenty of electricity to move air through its fins and cool the hot refrigerant gas that’s moving inside. At an outside temperature of 95 degrees, this is expensive.

Much more efficient are geothermal heating and cooling systems. A geothermal heat pump requires a good deal of space for installation, because coils need to be installed underground in a 50 by 100 foot square.

Alternatively, vertical holes can be drilled a couple of hundred feet into the ground, forming so-called geothermal loops. The purpose of this is to take advantage of the constant temperatures found below the surface. It’s the average annual temperature of the area.

For Gainesville, it means that you’ll encounter 58 degrees year round. This makes for much more efficient cooling during the hot summer months. But in winter, when the mercury drops to freezing, 58 degrees supplies a large amount of energy that can be used to heat the house.

Standard heat pumps, which draw heat from the outside air, lose efficiency rapidly when it’s below 50 degrees outdoors. They make up for it by activating a booster circuit that’s much less efficient because it uses resistance coil heat, similar to inexpensive space heaters from the hardware store.

Worldwatch Institute (www.worldwatch.org) estimates the installation cost of a geothermal heating and cooling system to be about $2,000-$4,000 higher than that of a new conventional setup. At current energy prices, Worldwatch estimates that the savings recover the extra cost in five to 10 years.

A quick search on the Internet shows a large number of companies in North Georgia who can handle installation of such a system. The 25- to 50-year life span of the coils makes it worthwhile to consider this option, especially in new construction.

The federal government offers a 30 percent tax credit until 2016.
And finally, geothermal systems greatly reduce carbon emissions that result from the production of electricity, which is progress toward the goal of minimizing future climate change.

Rudi Kiefer, Ph.D., is a Professor of Physical Science and Director of Sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.