Beginning in the 1970s, geothermal heat pumps came into common use. Geothermal heat pumps provide central air conditioning as well as heating as a matter of course. And they are installation-cost competitive with a central combustion furnace/central air conditioner combination.
Geothermal heat pumps operate by moving or transferring heat, rather than creating it. During the winter months, the geothermal heat pump refrigerant captures heat from outdoor air, compresses it and releases this warm air inside the home or business. During the summer, the process is reversed; the geothermal heat pump refrigerant captures heat from inside the home or business and transfers it to the pipes buried in the Earth.
Much less electricity is used to move heat rather than create it, making geothermal heat pumps more economical than resistance heating. Because they are working from those constant earth temperatures, the system provides more even temperatures throughout your home resulting in ultimate comfort to you and your family.
Depending on climate, geothermal heat pumps (including their supplementary resistance heat) are about 1.5 to 3 times more efficient than resistance heating alone. Operating efficiency has improved since the 70s, making their operating cost generally competitive with combustion-based systems, depending on local fuel prices. Another advantage to this system – there is no outdoor unit – thus no concern about outdoor noise.