The heating efficiency of a Geothermal Heat Pump, also known as a ground-source and water-source heat pump, is indicated by its coefficient of performance (COP), which is the ratio of heat provided in BTU per BTU of energy input. The cooling efficiency is indicated by the Energy Efficiency Ratio (EER), which is the ratio of the heat removed (in BTU per hour) to the electricity required (in watts) to run the unit.
Economics of Geothermal Heat Pumps
Although the purchase and installation cost of a residential Geothermal Heat Pump system is often higher than that of other heating and cooling systems, properly sized and installed Geothermal Heat Pumps deliver more energy per unit consumed than conventional systems. For further savings, Geothermal Heat Pumps are equipped with a device that can heat household water. In the summer cooling period, the heat removed from the house is used to heat the water for free. In the winter, water heating costs are reduced by about 50%.
Depending on factors such as climate, soil conditions, the system features you choose, and available financing and incentives, you may recoup your initial investment in a few years through lower utility bills. And your investment in a Geothermal Heat Pump may produce a positive cash flow from the beginning. It may also be possible to include the purchase of a Geothermal Heat Pump system in an “energy-efficient mortgage” that would cover this and other energy-saving improvements to the home. Banks and mortgage companies can provide more information on these loans.
Special financing and incentives are also available to help offset the cost of adding a Geothermal Heat Pump to your home. These provisions are available from federal, state, and local governments, power providers, and banks or mortgage companies that offer energy-efficient mortgage loans for energy-saving home improvements.
Evaluating Your Site for a Geothermal Heat Pump
Ground temperatures are relatively constant throughout the year, so geothermal heat pumps (GHPs) can be effectively used almost anywhere. However, the specific geological, hydrological, and spatial characteristics of your land will help your local system supplier and installer determine the best type of ground loop for your site.
Factors such as the composition and properties of your soil and rock (which can affect heat transfer rates) require consideration when designing a ground loop. For example, soil with good heat transfer properties requires less piping to gather a certain amount of heat than soil with poor heat transfer properties. The amount of soil available contributes to system design as well — system suppliers in areas with extensive hard rock or soil too shallow to trench may install vertical ground loops instead of horizontal loops.
Ground or surface water availability also plays a part in deciding what type of ground loop to use. Depending on factors such as depth, volume, and water quality, bodies of surface water can be used as a source of water for an open-loop system or as a repository for coils of piping in a closed-loop system. Groundwater can also be used as a source for open-loop systems, provided the water quality is suitable, and all ground water discharge regulations are met.
Before you purchase an open-loop system, be sure your system supplier or installer has fully investigated your site’s hydrology, so you can avoid potential problems such as aquifer depletion and groundwater contamination. Antifreeze fluids circulated through closed-loop systems generally pose little to no environmental hazard.
The amount and layout of your land, your landscaping, and the location of underground utilities or sprinkler systems also contribute to your design. Horizontal ground loops (generally the most economical) are typically used for newly constructed buildings with sufficient land. Vertical or more compact horizontal installations are often used for existing buildings because they minimize the disturbance to the landscape.
Benefits of Geothermal Heat Pump Systems
The biggest benefit of Geothermal Heat Pump systems is that they use 25% to 50% less electricity than conventional heating or cooling systems. This translates into Geothermal Heat Pumps using one unit of electricity to move three units of heat from the earth. Geothermal heat pumps can reduce energy consumption and corresponding emissions, up to 44% compared with air-source heat pumps and up to 72% compared with electric resistance heating with standard air-conditioning equipment. Geothermal Heat Pumps also improve humidity control by maintaining about 50% relative indoor humidity, making Geothermal Heat Pumps very effective in humid areas.
Geothermal heat pump systems allow for design flexibility and can be installed in both new and retrofit situations. In addition, the hardware may require less space than a conventional HVAC system, thus possibly freeing up space for other uses. GHP systems also provide excellent “zone” space conditioning, allowing different parts of your home to be heated or cooled to different temperatures.
The underground piping associated with Geothermal Heat Pumps systems often carries 25 to 50 years of warranty, and the heat pumps often last 20 years or more. In addition, the components in the living space are easily accessible, which increases the convenience factor and helps ensure that the upkeep is done on a timely basis.
Geothermal Heat Pumps have no outside condensing units like air conditioners, so there’s no concern about noise outside the home. A two-speed Geothermal Heat Pump system is so quiet that inside the house, users usually do not even know it is operating.