Learn More About GSHPs

1. What is a Ground-Source Heat Pump?

Heat naturally moves from warmer places to cooler places. Heat pumps use electricity to move heat in the opposite direction, from cooler places to warmer places, making the cool space cooler and the warm space warmer. Your refrigerator is a heat pump, moving heat from inside the refrigerated cabinet (cooler place) into your kitchen (warmer place). An air conditioner is a heat pump, moving heat from inside your home or business (cooler place) to the outside summer air (warmer place).

Heat pumps are also used to heat homes and businesses. A ground-source heat pump (GSHP) takes advantage of the fact that although many parts of the country experience seasonal temperature extremes -- from scorching heat in the summer to sub-zero cold in the winter—a few feet below the earth's surface the ground remains at a relatively constant temperature. Depending on latitude, ground temperatures range from 45°F to 75°F. Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer.

GSHP systems consist of three parts: the ground heat exchanger, the heat pump unit, and the air or hot water delivery system (ductwork or piping). The ground heat exchanger is a system of tubes called a loop, which is buried in the ground near the building. A fluid (usually water or a mixture of water and antifreeze) circulates through the tubing to absorb or relinquish heat within the ground. GSHPs require underground trenches or wells to operate, and a property needs to have sufficient space and the right geological conditions to support them.

In the winter, the heat pump extracts heat from the heat exchanger and pumps it into the indoor air or hot water delivery system, moving heat from the ground to the building's interior. In the summer, the process is reversed, and the heat pump moves heat from the indoor air into the heat exchanger, effectively moving the heat from indoors into the ground. The heat removed from the indoor air during the summer can also be used to heat water, providing a free source of hot water for sinks, showers, clothes washers, etc.

Heat pumps require electricity to run, but can deliver more energy than they use.

There are approximately 50,000 GSHPs installed at homes and businesses in the United States each year. As of late 2017, CMLP was aware of 21 private homes heated and cooled with GSHPs in Concord.


2. What is the advantage of installing a ground-source heat pump at my home or business?

These high-efficiency systems can provide 100% of a building’s heating and cooling needs. Though they require electricity to operate, efficient GSHPs can provide the same amount of heat using 65 to 80 percent less electricity than traditional baseboard electric heating – and reduce greenhouse gas emissions and operating costs accordingly.

Concordians also install ground source heat pumps because the systems reduce carbon emissions due to heating. This is a result of the combined high efficiency of the heat pump technology and the relatively lower carbon content of electricity, compared to other heating fuels.

Although the installation costs can be substantial, incentives and can reduce these costs, and in some cases, customers are cash flow positive from the day the system begins operation. This is more likely to be true when your investment in a GSHP is included in a mortgage. Due to their high efficiency, GSHPs offer excellent long-term energy savings as well.

For further savings, GHPs equipped with a device called a "desuperheater" can heat household water. In the summer cooling period, the heat that is taken from the house is used to heat the water for free. In the winter, water heating costs are reduced by about half.

GSHPs also improve humidity control by maintaining about 50% relative indoor humidity.

Ground-source heat pump systems allow for design flexibility and can be installed in both new and retrofit situations. Because the hardware requires less space than that needed by a conventional HVAC system, the equipment rooms can be greatly scaled down, freeing space for productive uses. GSHP systems also provide excellent "zone" space conditioning, allowing different parts of your home to be heated or cooled to different temperatures.

GSHP systems have relatively few moving parts and those parts are sheltered inside a building, so the systems are durable and highly reliable. The underground piping often carries warranties of 25 to 50 years, and the heat pumps often last 20 years or more. They usually have no outdoor compressors, so GSHPs are not susceptible to operational problems due to weather-related issues such as snow cover. 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.


3. What does a ground-source heat pump look like?

Ground-source heat pumps come in several varieties:

GSHPTypes

Ground-source heat pumps can move heat to and from the ground or to and from water (water-source), if there is a pond or other water body nearby. Local regulations apply.

Most closed-loop ground-source heat pumps circulate an antifreeze solution through a closed loop -- usually made of plastic tubing -- that is buried in the ground or submerged in water.

Diff Closed Loop Systems - GSHP
The loops can be horizontal or vertical, depending on land area available, soil conditions and other variables. If the site has an adequate water body, this may be the lowest cost option. A supply line pipe is run underground from the building to the water and coiled into circles at least eight feet under the surface to prevent freezing. The coils should only be placed in a water source that meets minimum volume, depth, and quality criteria.

Open loop systems use well or surface body water as the heat exchange fluid that circulates directly through the GSHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is obviously practical only where there is an adequate supply of relatively clean water, and all local codes and regulations regarding groundwater discharge are met.

Open Loop Systems - GSHP

The best system, loop length and design for a particular building depend on a variety of factors such as climate, soil conditions, available land, required heating and cooling load, and local installation costs at the site.

The indoor components of a ground source heat pump move the heat to and from the ground and around the house. These ground-source heating and cooling units were installed in the basement of a new home.

geothermal_heat_pumps_12333446


4. How much do ground-source heat pump systems cost?

The costs for GSHP projects in the 2 to 10 ton size range average $12,000 per heating ton, with 50% of projects ranging from $10,000 to $15,000 per heating ton, 20% above $15,000 per heating ton and 30% below $10,000 per heating ton, depending on the site and project type.

It is worth comparing the return on investing in ground source vs. air source heat pumps when considering heating options for your home or business. An air-source heat pump moves heat to and from the outdoor air rather than the ground. While air-source heat pumps are less efficient, they also cost less. For comparison, contractors are willing to install a one ton air-source heat pump unit (one outdoor unit + one wall- or ceiling-mounted unit) for $4,000 - $4,500, including electrical work. However, contractor prices can range from $3,000 to $7,000 for a single air-source heat pump, with an additional $350 - $800 for electrical work.


5. How can I learn more about ground-source heat pumps?

CMLP can put you in touch with Concord residents who have already installed ground-source heat pumps, and who would be happy to share information about their experience buying and using a ground-source heat pump. Contact Energy Specialist Pamela Cady at pcady@concordma.gov or 978-318-3149 for referrals.


6. How can I learn about the best ground-source heat pump options for my home or business?

We suggest soliciting proposals from at least three ground-source heat pump installers. Before soliciting proposals, consider talking with Concord residents and organizations who have already installed ground-source heat pumps. CMLP’s Energy Specialist, Pamela Cady (pcady@concordma.gov or 978-318-3149), can put you in touch with Concord residents who would be happy to share information about their experience buying and using a ground-source heat pump.


7. What questions should I ask potential ground-source heat pump installers?

Consider asking the following questions:

Qualifications and Experience

  1. Can you provide documentation that you hold one of the following credentials?
  • International Ground-Source Heat Pump Association (IGSHPA) Accreditation;
  • Certification as a GeoExchange Designer (CGD) from IGSHPA; or
  • Professional Engineer (“PE”) License from the National Society of Professional Engineers

    2. If not, can you provide at least three references from previous customers with similar systems?

Rebate

  1. Ground-source heat pumps that qualify for a MassCEC rebate in communities served by investor-owned utilities will qualify for a CMLP rebate (but not a MassCEC rebate) here in Concord. Do you install systems that qualify for MassCEC rebates in other towns?
  2. Are you familiar with the application process for CMLP’s ground-source heat pump rebate and are you willing to complete the process for me?

Installation Process

  1. When would you be able to perform the installation and how long will it take to complete?
  2. Will you hire subcontractors to complete portions of the project? If so, what firms and what will they do?
  3. Will you provide training for me on how to properly operate and maintain the system?
  4. Do you provide a warranty for the systems you install?