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What is a ground source heat pump?
Ground source heat pumps (GSHPs) are electrically powered systems that tap the stored energy of the greatest solar collector in existence: the earth. These systems use the earth's relatively constant temperature to provide heating, cooling, and hot water for homes and commercial buildings.

 

How do ground source heat pumps work?
Ground source heat pumps can be categorized as having closed or open loops, and those loops can be installed in three ways: horizontally, vertically, or in a pond/lake. The type chosen depends on the available land areas and the soil and rock type at the installation site. These factors will help determine the most economical choice for installation of the ground loop.

For closed loop systems, water or antifreeze solution is circulated through plastic pipes buried beneath the earth's surface. During the winter, the fluid collects heat from the earth and carries it through the system and into the building. During the summer, the system reverses itself to cool the building by pulling heat from the building, carrying it through the system and placing it in the ground. This process creates free hot water in the summer and delivers substantial hot water savings in the winter.

Open loop systems operate on the same principle as closed loop systems and can be installed where an adequate supply of suitable water is available and open discharge is feasible. Benefits similar to the closed loop system are obtained.

Residential
A GSHP system can be installed in a residential structure of any size, anywhere, whether it is single-family or multi-family. GSHPs can be installed on almost any size lot: under lawns, landscaped areas, driveways, or the house itself. An existing house can be retrofitted with a GSHP using the ductwork that is already there. Your dealer/installer will be able to determine ductwork requirements and if any minor modifications are needed. Home builders and homeowners can both take advantage of the special financing that is offered in many locations on a GSHP either through the utility or manufacturer.

The Department of Energy (DOE) and the Environmental Protection Agency (EPA) have both endorsed ground source heat pump systems as among the most energy efficient and environmentally friendly heating, cooling, and water heating systems available. In a 1993 report, the EPA concluded that geothermal technologies represent a major opportunity for reducing national energy use and pollution, while delivering comfort, reliability and savings to homeowners.

Ground Source Heat Pumps offer great benefits:

• Can be a combination heating/cooling and hot water heating system
• Can save you up to 50% on your water-heating bill by preheating tank water 
• Made of mechanical components that are either buried in the ground or located inside the home 
• About the same size as a traditional heating/cooling unit 
• Pipe carries up to a 50-year warranty 
• Keep the air warmer in the winter (90-105 F) and at a more consistent temperature throughout the home, eliminating the hot and cold spots common with other systems 
• Very quiet, providing a pleasant environment inside & outside the home 
• No noisy fan units to disturb outdoor activities 
• No exposed equipment outdoors; children or pets cannot injure themselves or damage exterior units 
• No open flame, flammable fuel or potentially dangerous fuel storage tanks

GSHPs offer great savings: 

• One of the most efficient residential heating and cooling systems available today 
• Heating efficiencies 50 to 70% higher than other heating systems and cooling efficiencies 20 to 40% higher than available air conditioners 
• Save money in operating and maintenance costs 
• Investments recouped in only a few years 
• Positive cash flow; energy savings usually exceed the cost of the system 
• Some utilities offer rebates or incentives to their customers who purchase GSHPs. To see what your state has to offer click here. 
• Many heat pump manufacturers, local utilities, and lending institutions have special financing for homeowners who are installing GSHPs

 

GSHPs are environmentally friendly:

• Conserve natural resources by providing climate control efficiently and thus lowering emissions 
• Minimize ozone layer destruction by using factory-sealed refrigeration systems, which will seldom or never have to be recharged 
• Uses underground loops to transfer heat, with no external venting and no air pollution
• The earth is a wonderful source of heat. Just ask the burrowing animals that depend on it for warmth in the winter. In fact, the earth stores 47 percent of the solar energy that reaches us, making it a natural source of heat for our homes, if we can get it out. And we can. Geothermal heating and cooling systems -- also called geoexchange, earth-loop, or ground-coupled heat pumps -- move the heat from the ground into your home using the same technology your refrigerator uses to remove heat from food. When a cat curls up at the bottom vent of a refrigerator, it simply is enjoying the warm result of the refrigeration process. That explains the heating process, but the system simply reverses to provide cooling during the hot months twice as efficiently as any other air conditioning system. It's an elegant solution to home climate control.
• The heart of a geothermal system is a cleanly designed box that looks like the average gas furnace, except that it replaces the fuel burner with a refrigeration system that converts heat from the earth into warmth for your home. Yes, geothermal systems use electricity, but because they only use it to move heat already available in the ground, they use a lot less than other electric heating systems.
• And a geothermal system can do more than heat and cool; it can provide virtually free hot water and superior home dehumidification.
• As documented by the Department of Energy and Environmental Protection Agency, geothermal heating and cooling is the most efficient home comfort system available, the "heating system for the 21st Century."
• 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.

 

Are incentives available from the state or federal government?
YES. Home and commercial building owners who install geothermal heating and cooling systems are now eligible for federal tax incentives under the American Recovery and Reinvestment Act of 2009 (H.R. 1: Div. B, Sec. 1122, p. 46), which removed the maximum credit amount for all eligible technologies (except fuel cells) placed in service after 2008. The legislation offers a one-time tax credit of 30 percent of the total investment for residential ground-loop or groundwater geothermal heat pump installations, with no limit on the maximum credit. To qualify for the tax credit, residential systems must meet Energy Star requirements. The contractor who sold and installed the product should list the purchase as a “geothermal heat pump” on the invoice and note that the unit “Exceeds requirements of the Energy Star program currently in effect.” The home served by the system does not have to be the taxpayer’s principal residence. The act also provides incentives for residential wind and solar systems, biomass, and efficient appliances and vehicles. Some states offer tax incentives, and some utilities offer rebates or special electric rates. You should check with a contractor to find out what's available in your area.

OK, so geothermal can provide cheap heat. Can it cool too?
It can do more than cool; it can make hot water, too. A simple switch at the thermostat reverses the process, allowing the geothermal system to provide cooling twice as efficiently as any other air conditioning system. In the process, the system provides virtually free hot water and superior home dehumidification plus, some units can make all of your hot water.

Heating Mode

Cooling Mode

Are we going to be comfortable?
Probably more comfortable than ever. A geothermal system moves warm air throughout your home via a standard duct network. Because the system moves a larger volume of air, heat is more even throughout the home and the initial cold air blast common with fossil fuel furnaces is eliminated. It's also a great comfort to know that you've reduced your energy consumption while using a renewable source - the earth. And geothermal means a cleaner house because there is no soot from combustion, and increased air flow means increased filtration.

Can a geothermal system be added to my furnace?
Split systems can easily be added to existing furnaces for those wishing to have a dual- fuel system. Dual-fuel systems use the geothermal unit as the main heating source and a fossil fuel furnace as a supplement in extremely cold weather if additional heat is needed. Your electric utility may provide special rates for dual-fuel installations.

Do I need separate loops for heating and cooling?
No. The same loop works for both. All that happens when changing from heating to cooling is that the flow of heat is reversed.

How do geothermal owners feel about them?
State and national surveys show that over 90 percent of owners are very satisfied with their geothermal units. More than 95 percent said they would choose the system again and recommended it to others.

Electric utilities like them because they use a lot of electricity, right?
Actually, utilities like geothermal systems because they use electricity in a way that benefits them and the customer. Because of the way they operate, geothermal systems provide a steady base load for utilities, pretty much avoiding the sharp peaks of electricity usage that require expensive reserve power sources. Those savings often are passed on to the customers in the form of special rates. And yes, geothermal systems use electricity, but because they only use it to move heat already available in the ground, they use a lot less than other electric heating systems. Geothermal systems operate at efficiencies 3 to 4 times higher than electric resistance heat. That is, a geothermal systems will provide 10,000-14,000 BTU's (British Thermal Units) of heat per kilowatt-hour compared with 3,413 BTU's per kWh produced by 100% efficient electric resistance heater. This also means that geothermal systems cost less-as much as 60 percent less to operate than propane or fuel oil furnaces.

How much groundwater does an open-loop system need?
Geothermal heat pumps used in open loop systems need differing amounts of water depending on the size of the unit and the manufacturer's specifications. The water requirement is usually expressed in gallons per minute (g.p.m.) Your heating contractor should be able to provide this information. Generally, the average system will use 6-10 g.p.m. An extremely hot or cold day might result in usage of 6,000-10,000 gallons of water. Your well pump combination should be large enough to supply the water needed by the geothermal unit and your domestic water requirements.

I wouldn't want to be a guinea pig for some new gadget.
The technology has been around since the 1950s. Tens of thousands of the units have been installed in all parts of the U.S. and Canada.

Is a geothermal heat pump difficult to install?
Most units are easy to install, especially when they are replacing another forced air system. They can be installed in areas unsuitable for fossil fuel furnaces because there is no combustion, thus, no need to vent exhaust gases. Ductwork must be installed in homes that don't have an existing air distribution system. The difficulty of installing ductwork will vary and should be assessed by a contractor.

If I have a pond near my home can I put a loop in it?
If it is at least six feet deep, a pond is a perfect heat exchanger.

My friend has a backhoe. Can we put in the loop ourselves and save a few bucks?
It's not recommended. In addition to thermal fusion of the pipe, good earth-to-soil contact is very important for successful loop operation. Nonprofessional installations may result in less than optimum system performance, and may void manufacturer's warranty. Look for qualified installers who guarantee their work and tell your friend to watch.

Should I buy a system large enough to heat my home with no supplemental heat?
Your contractor will calculate the heating and cooling load (heat loss/ heat gain) to guide equipment selection. Some new generation systems can be sized to meet optimum heating and cooling requirements without additional supplemental heat. Other models will supply 80-100 percent of your design heating load. Sizing the system to handle your entire heating needs may result in slightly lower heating costs, but the savings may not offset the added cost of the larger unit.

Is this magic? You can't get heat out of cold well water or the frozen earth.
The earth is a wonderful source of heat. Just ask the burrowing animals that depend on it for warmth in the winter. In fact, the earth stores 47 percent of the solar energy that reaches us, making it a natural source of heat for our homes, if we can get it out. And we can. Geothermal heating and cooling systems, also called earth loop, or ground-coupled heat pumps, move the heat from the ground into your home using the same technology your refrigerator uses to remove heat from food. When a cat curls up at the bottom vent of a refrigerator it simply is enjoying the warm result of the refrigeration process.

So what is this open-loop, closed-loop stuff?
The heart of the geothermal systems is the ground loop. An open-loop geothermal system uses well water as a heat source. As the water passes through it, the system extracts heat, reducing the water temperature about 5 degrees F. The water is then returned to the earth, usually by running it on the ground and letting it seep into the aquifer. A closed-loop system extracts heat from the earth by a series of liquid-filled pipes buried in the ground. The plastic pipes are filled with water and antifreeze. The pipe used in closed loop systems is buried beneath the frost line. The pipe can also be run vertically in bored holes. A typical home will have about 2,000 running feet of pipe in the earth loop. The pipe can have a guaranteed lifetime of 50 years or more.

How much does a geothermal system cost?
We get into trouble with dealers when we mention prices, because total installation cost depends on so many variables: unit size, type and style of loop, modifications to existing ductwork, among others. And the initial cost is more than offset by operating cost savings, which could be way more than half your current heating bill if you use propane or fuel oil.

Will an earth loop affect my lawn or landscape?
Well, digging a trench can get a little messy. But experience has shown that loops have no adverse effect on grass, trees or shrubs. Most horizontal loop installations use trenches about two feet wide. This of course, will leave temporary bare areas that can be restored with grass seed or sod. Vertical loops require little space and result in minimal disruption.