LINCOLN GREEN ENERGY

1.  What is a geothermal heat pump and how does it work?

Heat pumps do not create heat like electric resistance heating or like fossil fuel-fired heating systems; instead, they transfer heat from one place to another--much the same way that a refrigerator or air conditioner works except that it can move heat in both directions to provide both heating and cooling.

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Ground source (or geothermal) heat pumps (GSHPs) use the ground as a source of heat, while air source heat pumps use the outdoor air. One way to accomplish this is by running an anti-freeze solution through piping (“ground loop”) buried in the ground and using an indoor heat pump unit to extract heat from this anti-freeze. The indoor heat pump unit will then circulate this heat through your building like a traditional heating system. In the summer, this process is reversed and heat from your home is transferred into the ground.

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2.  What types of geothermal heat pumps and configurations are available?

There are different “types” of geothermal heat pumps based on variations in the type of ground loop and indoor unit configuration. The ground loop is the heat exchange surface for your heat pump. A home will typically need several hundred to thousand feet of piping in the ground loop to provide enough heat in the coldest part of the year. Ground loops are divided into “closed” and “open” loops:

• Closed loops use a continuous loop of buried piping, typically made out of high density polyethylene. A closed loop system will circulate a mixture of water and antifreeze that is not directly exposed to the environment. Most closed loop systems are installed in vertical configurations, in which the ground loop is run through multiple boreholes that are drilled several hundred feet deep into the ground . Most systems installed in Massachusetts are vertical closed loop systems. Some closed loop systems are installed in horizontal configurations, in which the ground loop is run through multiple trenches approximately 5 ft deep and around 300-400 feet long.

• Open loop systems can be used where there is an available source of groundwater available on the property from a well. Instead of circulating an antifreeze mixture, an open loop system will pump groundwater into the heat pump unit indoors for heat extraction before being safely returned to the ground. Open loop systems are typically cheaper to install and more efficient (due to the more consistent year-round temperature of groundwater), though they require a readily-available source of clean groundwater and may require additional permitting or environmental review.

• The indoor heat pump unit configuration will also vary depending on whether you use ductwork (forced hot air) or a hot water (hydronic) distribution system:

• A water-to-air system connects your indoor heat pump to a central air handler and uses your home’s existing ductwork to distribute heating and cooling throughout the home. Some modifications to your ductwork may be necessary to make it suitable for a geothermal system.

• A water-to-water system connects your heat pump to your existing hot water distribution system to provide heating. An air handler (and ductwork) is necessary to provide air conditioning.

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3.  What are the benefits of using geothermal heat pumps?

• Highest energy savings potential. Geothermal heat pumps are the most efficient heating and cooling system available--even more efficient than air source heat pumps. If you heat with oil, propane, or electric resistance heat, you could save hundreds to thousands of dollars a year on your heating bill by installing a geothermal heat pump. No need to pay thousands of dollars just to get a gas connection to your home: a cleaner, more efficient alternative is already available.

• Greatly reduce your carbon footprint. As the most efficient clean heating and cooling  technology available, geothermal heat pumps will greatly reduce your carbon footprint and dependence on imported fossil fuels. Using solar PV or other renewable electricity sources can further offset emissions from the electricity powering your heat pump. If you’re looking for the most environmentally-friendly heating and cooling system, look no further.

• A clean, whole-home solution. Geothermal can offer a clean whole-home heating and cooling solution without requiring backup heating. Eliminate fossil fuel combustion and associated risks from your home entirely. Geothermal can also heat 40-50% of your home’s domestic hot water at no additional operating cost with an add-on.

• No exposed outdoor components. Compared to central air conditioners and air source heat pumps, there are no outdoor components for a geothermal system that are exposed to the elements that are not buried safely underground.

• Geothermal systems come with  monitoring system installed. This will allow the company to receive alerts, diagnose errors, and perform maintenance remotely, only needing to come out to your home when hands-on maintenance is required.

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4.  Are there drawbacks to geothermal heat pumps?

While GSHPs can be a great fit for many homes and businesses, they are not without a few drawbacks:

• High upfront costs. GSHPs are very expensive to install, with most systems costing at least $20,000 after incentives. While their significant energy savings pay for themselves, they can take several years to pay back the difference compared to traditional fossil fuel or central AC systems.

• Landscaping considerations. GSHP systems require drilling or excavation in your yard or lot. Vertical loop systems require the least disruption to your property, though there will still be some disturbance associated with the drilling process and moving drilling equipment around. Ask your installer about what options there are for minimizing disruptions and restoring landscaping after installation.

• Installation time. As system design and drilling/excavation is required, the geothermal installation process can take a week or more to complete. If you need a heating or cooling system replacement quickly, a GSHP system may not be well-suited for an emergency replacement.

• Ductwork installation or modification may be required. Geothermal systems can offer both heating and cooling, but there may be some limitations to the existing distribution systems with which a GSHP system will work. While geothermal heat pumps can work with hydronic (hot water) distribution systems, they are not compatible with steam heating systems. Ductwork is required for your geothermal system to provide air conditioning. Even if you already have ducts, some modifications may be necessary to adapt your ductwork for geothermal.

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5.  Is a geothermal heat pump right for me? 

GSHP retrofits can work in most homes. If you answer “Yes” to any of the questions below, a geothermal system may be a good fit for you:

• Do you heat with oil, propane or electric resistance?

• Do you want whole-home central air conditioning and heating in one system?

• Are you concerned about the aesthetics of air source heat pumps?

• Do you want the most efficient, environmentally-friendly system available?

• Is your boiler/furnace or central AC system 15+ years old?

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6.  Why are geothermal heat pumps considered “clean heating and cooling” technologies?

Geothermal heat pumps are considered to be “clean” heating and cooling systems because they do not create heat, but rather they transfer  heat from the ground into your building. This process is powered by electricity, which can also be sourced from renewable sources like solar, wind, or hydro.

Even though our grid is only about 16% (2020) renewable today (and getting 2% greener every year), a GSHP system powered by grid electricity will reduce your greenhouse gas emissions from heating by 30-75+%! Plus GSHPs are very efficient!

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7.  Can geothermal heat pumps provide domestic hot water?

Yes. Geothermal systems can be installed with desuperheaters that can provide you with about half of your home’s annual hot water needs. A geothermal system operating in cooling mode will typically store unwanted heat in the ground. A desuperheater will use that waste heat to pre-heat your hot water before it enters your hot water tank. A desuperheater add-on will cost around $1,800 but will save lots on your heating bill!

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8.  How do the annual maintenance costs of geothermal heat pumps compare to other heating systems?

Geothermal systems require relatively little maintenance. The ground loop is designed to last for up to 50 years or more (you can even purchase an extended warranty against any leakage for 55 years!), and no other components are exposed to the elements. Periodic checkups and filter changes are the most common maintenance requirements. Other adjustments to your system performance can be done remotely through a monitoring system.

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9.  How long do geothermal heat pumps last?

The ground loop piping is designed to last for up to 50 years or more. The indoor heat pump unit has a life expectancy of around 20 years, similar to conventional heating and cooling systems. Some pumps, controllers, or other components may require replacement sooner than the indoor unit.

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10.  How complicated is installing a geothermal heat pump and how much time will it take?

After your installer conducts a site visit the company then drew up a proposal.  Installation could then take 2-3 months after the contract is signed. This time includes:

• Rebate pre-approval (1-3 weeks). 

• Equipment ordering (1-2 weeks). Once the rebate is approved, 

• Drilling/excavation, installation, and commissioning (4-5 weeks). 

• Inspections (~2 weeks). This will depend on the town inspector’s availability to come out to your home.

This timeline might vary.

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11.  What if I don’t have a lot of yard space?

You only need a lot of space for a horizontal ground loop installation. A vertical closed-loop system will require only a few boreholes and can take up as little space as your driveway.

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12.  How much will an geothermal heat pump cost?

The cost of a geothermal heat pump system will range due to the customization needed for your home and the difference in incentives. Typically geothermal systems will start at $20,000 after incentives. A detailed version from Lincoln’s HeatSmart program is  available here.

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