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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).[i]
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.[ii]
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 shallow 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.[iii]
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.[iv]
Heat pumps require electricity to run, but can deliver more energy than they use.[v]
There are approximately 50,000 GSHPs installed at homes and businesses in the United States each year.[vi] As of late 2017, CMLP was aware of nine private homes heated and cooled with GSHPs in Concord.[vii]
[i] Bob Zogg. HP Presentation –2017-02-04.pdf
[vii] Heat Pump Coaches List.xls in Heat Pump Rebate folder. Potential Coaches spreadsheet.
These high-efficiency systems can provide 100% of a building’s heating and cooling needs.[i] 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.[ii]
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.[iii]. Due to their high efficiency, GSHPs offer excellent long-term energy savings as well.[iv]
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.[v]
GSHPs also improve humidity control by maintaining about 50% relative indoor humidity.[vi]
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.[vii]
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 GHPs are not susceptible to vandalism. 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.[viii]
Ground-source heat pumps come in several varieties:[i]
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.
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.[ii]
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.[iii]
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.[iv]
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.[v]
[i] Bob Zogg. HP Presentation –2017-02-04.pdf p 39
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.[i]
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.[ii]
[i] MassCEC GSHP project database, reviewed on 1/2/18, and saved as file ResidentialandSmallScaleGSHPProjectDataBase010218.xlsx in GSHP Rebate Program folder.
[ii] Sagewell, Inc. June 2016. Heat Pump Program Design Questions. P20.
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 email@example.com or 978-318-3149 for referrals.
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 (firstname.lastname@example.org 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.
Consider asking the following questions:
Qualifications and Experience
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
Ground-source heat pumps installed at new or existing buildings are eligible for rebates, though the system must be used for heating (in addition to heating use, systems may providing cooling as well). Projects with a single heat pump serving multiple units in a multifamily residential or multi-unit commercial building can apply jointly with one application, subject to existing caps. A single apartment or condominium can also apply individually. Projects must have rated heating capacity no greater than 10 tons (120 kBTU/hr).
Project installation may not commence until after the application has been approved by CMLP and the system owner has received an award letter. Projects that have already commenced construction are not eligible for the rebate.
Energy Audit Requirement
All existing buildings must have an energy efficiency audit completed within the past four years or have an energy audit scheduled to occur and completed within six months of project completion. CMLP highly recommends that priority recommendations from the audit be implemented before or in coordination with the installation of the GSHP. Making a building more energy efficient can reduce the size and cost of the GSHP needed to heat and cool your building.
Households heating with natural gas can contact MassSAVE at (866) 527-SAVE (7283) or masssave.com/en/saving/energy-assessments/ for an audit. Businesses heating with natural gas can find information about Mass Save facility audits at https://www.masssave.com/en/saving/business-rebates/facility-assessments/
All others can sign up with Energy New England at email@example.com, (888) 772-4242, or ene. org/residential-audits/. Energy New England, CMLP’s energy audit provider, provides no-cost home energy audits, and business energy audits at a 50% discount. CMLP covers 50% of the cost of a full-scale business energy audit.
New buildings do not require energy audits, although energy audits are still recommended.
Rebate levels for GSHP systems are calculated per heating ton (12,000 BTU/hr). Residential rebates are limited to the first five tons of heating capacity per housing unit. Non-residential entities can receive funding for up to ten tons of heating capacity through this program. Income-based rebates are available for qualifying residential applicants.
If the project meets the above eligibility requirements, system owners should next determine which rebate type they are eligible for based on the following table:
Income-Based Thresholds by Household Size
$625 per 12,000 BTU/hr**
(up to a maximum rebate of $6,250)
Annual Gross Income
(up to a maximum rebate of $3,125)
$800 per 12,000 BTU/hr**
(up to a maximum rebate of $4,000)
$1,500 per 12,000 BTU/hr**
(up to a maximum rebate of $7,500)
*To receive an income-based rebate, the customer must complete one of the accepted income verification methods. Please see the “How Do I Qualify for an Income-Based Rebate?” question below for more information about income-based rebates and income verification.
**For the purposes of determining rebate levels for GSHPs, CMLP uses the American Heating and Refrigeration Institute’s (AHRI’s) heating capacity for the system.
All applications must be submitted and approved by CMLP prior to starting project construction, and, to be eligible for a rebate, construction must not commence until an award letter is issued. Once the system owner has decided to move forward with the project, the installer should apply for a rebate on the system owner’s behalf.
First, select a GSHP installer, who will submit the rebate application on your behalf.
The following resources can help you identify potential installers:
The Massachusetts Clean Energy Center, which administers a GSHP rebate program primarily in communities without municipal light plants, maintains a list of installers who have previously participated in their program. Go to http://www.masscec.com/ground-source-heat-pump-installers to download the list. Using an installer from this list is NOT required to receive a CMLP rebate.
The following directories can also help you identify installers:
New England Geothermal Professional Association (NEGPA)
International Ground-Source Heat Pump Association (IGSHPA)
In order for your GHSP installation to be eligible for a CMLP rebate, the following conditions must be met:
Your installer must actively hold one of the following credentials:
Professional Engineer (“PE”) License from the National Society of Professional Engineers.
Your installer must submit a copy of the certificate for one of the accreditations listed above with the rebate application.
If not currently holding one of these credentials, your installer must provide references for three GSHP installations, including phone numbers and email addresses for each reference. Rebate approval is contingent upon a successful reference check. Installers must achieve one of the above credentials within one year of submitting their first GSHP rebate application to CMLP in order to be eligible to submit further GSHP rebate applications to CMLP.
CMLP recommends that our customers:
In order to be eligible for a rebate, projects must meet the following requirements:
CMLP may choose to monitor a subset of systems installed under this program. To be eligible for a rebate under this program, the system owner must agree to allow metering and monitoring to be conducted on their project for up to twenty-four (24) months after installation, if requested. The system owner will be required to submit fossil fuel bills for two (2) years prior to installation (for existing buildings) and for the duration of the performance monitoring. Monitoring equipment would be paid for and installed directly by contractors to CMLP with no direct cost to the system owner. Data would be collected and analyzed for program evaluation purposes and will not impact the rebate received by the system owner.
Although CMLP typically does not allow deviation from these design requirements, certain site characteristics may lend themselves to alternate system designs. If for technical reasons, a design requirement cannot be met for an installation, the installer may request a waiver. All variations must be explained in detail in the Project Notes field at the bottom of the application, and output from geothermal modeling software must be submitted. CMLP may send these applications to CMLP’s third party consultant for review and consideration.
Step 3: Apply for a Rebate
Prior to deciding to move forward with a system, residents who may meet income criteria should determine if they are eligible for the Income-Based Rebate, as described under the “Who’s Eligible for a Rebate?” question above. For example, a household of four with annual income of $132,230 or less may qualify. If eligible, complete one of the three income verification methods described in the “How do I qualify for an Income Based Rebate?” question below.
In the interest of increasing access to ground-source heat pumps to all residents of Concord, CMLP offers additional incentives for households with income below eighty percent (80%) and one-hundred-twenty percent (120%) of the state median income. Eligibility thresholds are determined based on household size. Eligibility for the income-based rebate is based on the income of the system owner’s household.
Eligibility is based on total household income (Tax Return Form 1040 line 22), as determined by the System Owner and Household Members’ federal income tax filings for the most recent year available. Each System Owner household is only eligible to receive the income-based rebate at one residence.
Income-Based Rebate Adder Thresholds by Household Size
80% of State Median Income
120% of State Median Income
To receive the Income-Based Rebate, the System Owner must complete one of the following three income verification methods:
GSHPs are exempt from the 6.25% state sales tax.[i]
[ii] Achieve Renewable Energy’s GSHP Customer Proposal (January 2018), as included in HeatSmart Mass proposal
Contact Pamela Cady, CMLP’s Energy Specialist, at firstname.lastname@example.org or 978-318-3149.