The temperature in the ground around your house is fairly constant year round, and that's the secret behind the efficiency of geothermal heating and cooling systems. That constant temperature - roughly 46 to 50 degrees F. in northern states and warmer as you travel south - allows already efficient electric heat pumps to operate for even less, reducing the cost of heating your home by more than half when compared with a propane furnace. And geothermal systems provide cooling at up to a third less than conventional central air conditioning systems.
Geothermal systems will work for any house, old or new, whether delivering forced air through ductwork or heated liquid through radiant tubing in the floor.
While the initial cost of a geothermal system is marginally higher than the cost of a comparable fossil fuel furnace with central air, the lower operating cost will make up for the extra cost several times over the lifetime of the equipment. In fact, when the cost of the geothermal system is included in the mortgage, the combined living expenses for mortgage and heating and cooling will be less than for the same house with a fossil fuel system. In other words, the lower energy bill for a geothermal home more than offsets the higher monthly mortgage payment. That's money in your pocket.