Is geothermal heating worth the cost?

When it comes to cheap, renewable energy, nothing seems more reliable than sucking heat from Mother Earth. Geothermal heating and cooling has been around for 20 years or more, but it remains unknown to most people—we didn't know about it until a friend installed it, and neighbors hadn't heard of it until a huge drilling rig began the noisy, two-day process of boring holes in our small back yard.

Closed loops of plastic tubing now fill the four, 200-foot-deep holes. A mix of water and refrigerant (eco-friendly, of course) will soon pump through the tubes, returning to the house at the steady temperature of 55 degrees Fahrenheit, which is the ground temperature in St. Louis, where we live. That's chilly enough to cool our house in the summer, while compression will raise the fluid's temperature to heat our house on cold days. The conditioned air will circulate through conventional, forced-air ducts.

Geothermal should cut our heating and cooling bills in half or so. Another advantage is more subtle, but still attractive: The air moves steadily and quietly, unlike the whooshing of our conventional system kicking in. Additionally, the outside elements of our conventional AC go away; there will be no ugly compressor to hide behind bushes.

The biggest disadvantage is cost—in our case, about $10,000 more than a conventional system. (Most of that difference lies underground in those four holes.) Even with today's inflated energy prices, it will take six or eight years for payback. And the cost might be prohibitive for someone with a system that's working well; we had already planned to replace our aging furnace as part of a major remodeling. Finally, the 32-ton drilling rig turned our backyard into a mud pile. But out of that muck I hope savings will soon flow—dollars in several tints of green.