What it means. Earth energy is the newfangled name for the time-honored tradition of tapping the earth’s underground energy to heat or cool a building by running various liquids through a network of buried pipes. You’ll often see the term as part of an earth-energy system, or EES.

“Geothermal had always been the name for our earth-energy process, and it was confusing because everyone was expecting to see hot water coming out of the ground,” says Mark Morelli of Santa Rosa, California-based Air Connection, Inc. “Then my company shifted to calling it a ‘GeoExchange’ system, but ‘earth energy’ makes it easier for people to relate to what we do.”

“Earth energy certainly reflects what an EES does, which is to use the heat of the ground to both heat and cool your home,” says Greg Dudley, a sales manager at Earth Energy Technology & Supply in Marietta, Oklahoma.

Why the buzz? As Americans seek alternatives to fossil-fuel-generated energy, interest in renewable energy has grown—Morelli and Dudley report that their businesses have boomed in the past year—as has its profile. Al Gore in mid-July called for Americans to wean themselves of electricity generated by fossil fuels.

Earth-energy systems are one way to decrease our fossil-fuel reliance. In its most-efficient form, an EES takes the form of a ground-source heat pump. Throughout the U.S., the temperature just a few yards below the surface hovers around 55°F. Running groundwater, an antifreeze mixture, or a refrigerant through pipes and into the pump in your home will produce heat for home heating and hot water. Reverse the flow during cooling season, and the system will remove excess heat from your home and cool your indoor spaces. (See the illustration, courtesy of the California Energy Commission, above.)

While EES are not mainstream, people are talking about them. Members of the Consumer Reports HVAC forum, for instance, are discussing earth energy, with posters sharing information and links, like this one to the California Energy Commission’s Web page on geothermal heat pumps.

A typical EES will run two to four times as much to buy and install as a conventional oil- or natural-gas-fired heating-and-cooling system. But given the rising carbon-based fuel prices and the lower annual operating costs for an EES, a system could conceivably pay for itself within a few years in the best-case scenario, according to industry experts. Payback time will vary depending on a number of factors. High costs of electricity and installation (drilling is pricier in rocky soil) and a colder climate will increase how long it takes to break even.

What’s more, petroleum-based polyethylene pipes used in many earth-energy systems are getting more expensive and, and installers are likely to pass on that cost to you. And unlike solar-power systems, earth-energy systems don’t benefit from the wide array of utility rebates and state and federal tax incentives, although the earth-energy industry is lobbying to change that.—Gian Trotta

via ConsumerReports.org