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.

Ground source (or geothermal) heat pumps use the ground as a source of heat, while air source heat pumps use the outdoor air. Achieve's geothermal heat pumps accomplish this 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 water. 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.

There are different “types” of geothermal heat pumps based on variations in the type of ground loop and indoor unit configuration.

Ground loop. 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 (see below). 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 (see below).
  
• 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.

There are numerous benefits to 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 CH&C 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.
• Remote maintenance. The geothermal systems installed by Achieve come with the Symphony monitoring system installed. This will allow Achieve to receive alerts, diagnose errors, and perform maintenance remotely, only needing to come out to your home when hands-on maintenance is required.

While GSHPs can be a great fit for many Carlisle, Concord, and Lincoln 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 to install. 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 Achieve about what options there are for minimizing disruptions and restoring landscaping after installation.
• Installation time. As system designing 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 can 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.

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?

Geothermal heat pumps are considered to be “clean” heating and cooling systems because they do not create heat, but rather they transfer renewable 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 12% renewable today (and getting greener every year), a GSHP system powered by grid electricity will reduce your greenhouse gas emissions from heating by 30-75+%!

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 cost nothing extra to operate!

Our installer Achieve will visit your home within 2 weeks of you signing up for a site visit. If geothermal is suitable for your home, Achieve will present you with a customer proposal within a week of your site visit. A geothermal installation will typically take 2-3 months to complete from when you sign a contract. This includes:

• Rebate pre-approval (1-3 weeks). Achieve will submit your application to MassCEC for rebate pre-approval prior to commencing work.
• Equipment ordering (1-2 weeks). Once the rebate is approved, Achieve will order the equipment for your home.
• Drilling/excavation, installation, and commissioning (4-5 weeks). Over this period of time, Achieve will drill/excavate and install your system. After the installation is complete, Achieve will commission your system and educate you on how to use your new geothermal system.
• Inspections (~2 weeks). This will depend on what town you're in and when the inspector is available to come out to your home.

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.