Heat from the Ground
Once the loop is completed, it's hooked up to a "ground source heat pump." Selby says that lately, the introduction of dual-stage compressors has made these even more efficient. But he feels that the most important recent development in geothermal is psychological: there's now widespread interest. Geothermal seems to have entered the public consciousness.
Asked how long it takes for a geothermal system to pay for itself, he says, "Somewhere around three to seven [years] if propane or fuel oil's being used and around seven to twelve years if it's natural gas." Will a system last that long? "Mostly the components last a long time if the system's well made," he says, "but occasionally you have to change a compressor after about ten years."
One of Selby's customers, John Swerdlow, admits that he and his partner, Pamela Harnick, "weren't looking for a 'green' house. We just wanted one with two bathrooms on the second floor." But after eighteen months of fruitless searching for an existing home that met their needs, "Doug suggested he could find a location we could live with and build what we wanted. So that's the way we went."