Ground source heat pumps (GSHPs), often called geothermal heat pumps, tap into the heat naturally generated many meters below the surface of the earth. Just a little ways down, the earth's temperature is warm and relatively stable, so these systems can bring controllable and effective heating, cooling, and hot water to residential and commercial buildings. Best of all, they allow people to do all this without having to use expensive and carbon-producing fossil fuels such as oil and gas.

There are two types of ground source heat pump systems: those with closed loops and those with open loops. In closed loop systems, liquid (usually with some sort of antifreezing/antiboiling agent mixed in) circulates through pipes buried beneath the earth's surface. During the winter, when the goal is warming a house, the fluid absorbs heat from the earth and carries back to the building. This very hot liquid can be effectively used to heat a home, and also quite obviously becomes a free-flowing source of useable hot water. During the summer, the system is designed to actually draw heat out of the building, and either use it to heat water for household use or deliver it back into the ground. Open looped systems are similar, except that the water supply within the pipes is continually refreshed.

The bulk of geothermal (GSHP) systems are the pipes that are buried far underground, so what is needed in your home is a unit likely no bigger than your current hot water heater and furnace. If you currently use oil, you may be able to get rid of or at least substantially downsize the size of your oil tank. Many people worry about the longevity and upkeep costs of this type of system because the bulk of the cost goes into burying the pipe underground. Recently however many companies have been offering 40-75 year warranties on the parts of the system that is buried.

If you already have a forced air oil or gas-fed furnace system it may be easy for you to convert to what is called a "dual system". In this case you would choose which heating and cooling system would be primary at any particular time - most likely the geothermal system - and the other system will only work when needed, such as during an extremely cold spell in the winter.

GSHPs are quiet and safe. There are no exposed parts, fans, storage tanks, etc. that can hurt kids or pets. Nothing is burned so there is no flame. The heating source is the earth so there is nothing to wear out. They are also quiet because the earth is doing the work of the motors in your current furnace.

The initial cost for ground source heat pumps is greater than that of a conventional oil or gas system. However, that initial cost is often made up in three to six years depending on the cost of fuel and the temperature in your area. The greatest benefit of these systems is that you no longer have to use oil or gas at all, so not only are you not subject to the price fluctuations and uncertainty of these fuels, but you also reduce your own "carbon footprint" in the process.

Ground source systems are easy to install, particularly when they are replacing another forced-air system. In this case it is as simple as a retrofit after the pipes are placed. However, they can also be installed to completely replace the system you already have. If you don't already have central air conditioning, that can be an automatic and immediate benefit of these systems. Contact an experienced installer and he or she can tell you exactly what would be involved in installing a geothermal heat pump in your home.