There's a certain elegance to the environmentalism of geothermal heat pumps. These systems help reduce your home's impact on the planet by tapping into the earth itself, using its constant temperature to both heat and cool your home.

Unlike air source heat pumps, which draw heat from outside or send hot air from the home to the outdoors, geothermal heat pumps rely on the steady temperatures in the ground. Max Alexander, writing for This Old House, says underground temperatures reach about 50 degrees at a certain depth, no matter what the air temperature is.

Geothermal heat pumps use a system of subterranean looping pipes to circulate a liquid such as water or antifreeze. The magazine Family Handyman says the system works similar to a refrigerator's coils, which extract heat from the interior space. A pump located within your home circulates heat from the ground during the winter. In the summer, this flow can be reversed to send heat from inside your home into the ground.

Homeowners can realize a number of benefits from geothermal heat pumps. However, they should also be aware of the downsides of the system before making the investment.

Benefits

Most homeowners who purchase a geothermal heat pump system will want to see significant savings, and the technology certainly delivers in this area. Alexander says geothermal heat pumps can reduce your utility bills by up to 70 percent. Family Handyman says you can easily see savings of up to 60 percent on your heating costs while cutting your cooling costs in half.

These steep drops in energy costs will also speed up the payback period. The Department of Energy says these savings can offset your upfront costs within two to 10 years.

Upgrading your home's heating and cooling system will also qualify you for a number of incentives, such as rebates. These incentives may be offered through government programs, local utilities, mortgage companies, or lenders.

Since the system works by transferring heat from one location to another, it minimizes your use of fossil fuels. The system does not require you to burn any fuel, and the only use of fossil fuel might stem from the electricity required to run the pump. Family Handyman says this avoids risks such as fire hazards and carbon monoxide production associated with traditional furnaces, and it also has the environmental benefit of reducing your home's greenhouse gas emissions.

Geothermal heat pumps are typically much quieter than other types of heating or cooling systems. They do not rely on noisy burners, fans, or compressors, and are generally about as loud as a refrigerator.

The system is usually rated to last for many years. The ground loop system can last for 50 years or more, and the interior components often won't need to be replaced for 25 years.

Some units are able to use some of the transferred heat for your domestic hot water. The Department of Energy says the systems are usually able to cover all of your hot water needs during the summer, while halving this expense in the winter.

Disadvantages

Many homeowners are caught off guard by the high upfront cost of installing a geothermal heat pump. Family Handyman says the system is easiest to incorporate into new construction, but can still cost 40 percent more than a traditional HVAC system. Excavation, the modification of a home's ducts, and other work can all result in a bill of tens of thousands of dollars.

Some of the cost is related to the type of system. A geothermal heat pump is most cost effective if you have a body of water on your property, since the coils can simply be submerged to take advantage of heat transfer in the water. Other systems may require you to dig up a large area of your yard or, if space is limited, drill openings for the pipes several hundred feet deep into the earth.

Geothermal heat pumps are complex systems which require a professional installation. This means you won't be able to do the work on your own to save money.

Conditions at your home will also affect the cost of the project. Maxwell says it is more expensive to drill down than to bury the coils at a shallower depth, particularly if your property is built on ledge.

Digging into your yard may require you to temporarily sacrifice your perfectly manicured lawn or other landscaping features. You'll then need to spend the time and possibly invest some extra money to restore your yard.

A geothermal heat pump won't work effectively if it is not sized correctly for your home. Angie Hicks, writing for Angie's List, says the company installing the system should first perform a Manual "J" load calculation to determine how much air is needed to keep a room comfortably warm or cool.

When a system is not sized correctly, it won't be enough to maintain a comfortable temperature in your home. Jordann Brown, writing for the Canadian heat pump company Maritime Geothermal Ltd., says homeowners may be tempted to get an undersized system to save money. However, doing so will result in a less comfortable home and may force you to use backup heating sources, negating any cost savings you would see with a correctly sized system.