A primer/Q&A on heat pumps follows, below. Also, see the information on the Abode/Acton website. As of 2023, you may also contact a volunteer Acton Energy Coach with this Coaching Request Form.

What are heat pumps?

Traditional heating systems burn fuel to create heat; heat pumps work by “pumping” heat into or out of a building or home. Though they require electricity to operate, heat pumps use only 20–50% of the electricity that would be used by traditional electric resistance heaters. A heat pump can supplement your existing heating system or completely replace it. Heat pumps provide the greatest economic benefit if your home is currently heated with oil, propane, or electric baseboards, but many will find it affordable to replace gas heat now or in the near future. Here are some more-detailed resources on heat pumps:
• Energy Sage
• Massachusetts Clean Energy Center (MassCEC)

How important are heat pumps for meeting Acton’s net zero carbon goal?

For most Acton households, the single most impactful Action to cut carbon emissions is to stop burning oil, gas, or propane for heat, and switch to an electric heat pump system. As the table below shows, this can cut an average of 3.2 tons of carbon (MTCO2e) every year; the reduction will be a little greater for homes previously heated with oil, and a bit less for those using gas.

Heat pumps are even more impactful when the electricity to power them is 100% renewably sourced — in Acton, e.g., renewable supply is readily available through Acton Power Choice GREEN. The emissions reduction realized by using 100% renewable, zero-emission electricity for your heat pump system will average about 2 tons annually on top of the 1.5 ton reduction from “greening” (using 100% renewable) the rest of the electricity used by the average household.

The Top 6 Actions for Cutting Household Carbon Emissions:
Average Tons Reduced/Year

Sources: MassEnergize Carbon Calculator Methodolgy, Energize Acton conversions to metric tons based on 2,204.62 pounds/metric ton. 

Reductions will vary from one household to the next, depending on the particulars, but if a household’s members can do all the things in this table (there are 6 Actions listed; all the APC Green actions are counted as one), they would eliminate approximately 13 tons of carbon from their emissions each year. This is roughly 74% of the average 17.5 tons of emissions per household counted in the 2019 Acton Greenhouse Gas Inventory from home energy use and passenger cars in Acton. (Note: on-site solar was omitted from the 13 ton total because most of solar’s potential emissions reduction is achieved in this scenario by APC GREEN.) 

At the beginning of 2022, 138 Acton buildings had heat pump systems installed. Energize Acton has a goal of another 130 buildings converted to heat pumps by the end of 2022 as part of reaching net zero carbon emissions Town-wide by 2030, for a total of 268 by year-end.

What is the basis for the estimate of 3.2 tons/year emission reduction?

This estimate of emissions reduction is intended as an approximation of typical, average, or potential results in order to convey relative magnitudes of various Actions; this is not a prediction of actual results of individual heat pump installations. Using MassEnergize Carbon Calculator Methodology, MassEnergize estimated a 7,199 pounds/year reduction by assuming that an oil furnace is partially displaced by a high-efficiency, central ducted air-source heat pump, with energy savings from the Technical Reference Manual used for evaluation of MassSave programs. For this partial displacement scenario, it appears that this MassSave analysis had assumed HSPF (Heating Seasonal Performance Factor) values for heat pumps from 8.2–9.6, which are relatively inefficient (i.e., lower than the HSPFs up to 12 for ductless mini-split heat pumps [ductless mini-split heat pumps/DMSHP]).

Source: Energy Optimization Study, October 9, 2018, Table 3, page 7. More generally, it may be possible to achieve better emission reductions if existing oil burners are removed, even if electric resistance heat is used for backup during very cold hours/days.

How does the electricity emission factor affect the emissions reduction estimates?

MassEnergize uses an electricity emissions factor of 580 Lb/MWh from MassDEP. Energize Acton converted to metric tons using 2,204.62 pounds/metric ton. Notes on electricity emissions factor: The DEP factor of 580 Lb/MWh is for Massachusetts as of 2017. Energize Acton estimates that, since then, that factor should have dropped by about 11% through 2021, to 517 — based on trends of ISO-NE’s average emission factor for 2018 and 2019, and then adjusted for remaining years based on the increase in the RPS Standard (2% per year). The APC Standard option should be about 12% lower than 517, reaching about 454 Lb/MWh, based on its additional renewable content above RPS. Based on these trends, the emissions reduction estimates for air-source heat pumps could be reduced by 21.7%, to reflect the change in emissions factor from 580 to 454 — from 3.2 to 2.5. However, Energize Acton is not making this change for three reasons: (1) the ISO-NE factors for 2017 — 682 Lb/MWh average and 654 marginal — are higher than the 580 Mass DEP factor and better represent the regional wholesale market from which Acton Power Choice buys electricity; (2) we expect that heat pump performance will have improved since the MassSave estimate was derived; and (3) we want to use consistent impact estimates to allow future comparisons with other MassEnergize towns.)

What incentives are available for heat pumps?

All homes qualify for heat pump incentives from MassSave. Some homes may qualify for additional incentives from Massachusetts state agencies. Make sure to obtain the most-current information on incentives because they may change. For ground source heat pumps there are rebates of up to $10,000 and a generous federal tax credit, with higher incentives for low- and moderate-income customers.

What is the difference between “air source” and “ground source” heat pumps?

There are two basic types of heat pumps:

• Air-Source Heat Pumps (ASHPs) exchange heat with the air outside your home. Some ASHPs are efficient down to sub-zero outdoor temperatures. ASHPs for homes that already have ducting are called central heat pumps, while so-called ductless “mini-splits” are suited for homes that don’t have existing ducting. All ASHPs provide energy-efficient heating and cooling for your home. ASHPs use 30–50 pecent as much electricity as traditional electric resistance heaters, such as electric baseboards. Download the NEEP Air-Source Heat Pump Buyers Guide  for more information. 

• Ground-Source Heat Pumps (GSHPs) can provide highly efficient heating, cooling, and water heating by utilizing the nearly constant temperature underground to heat or cool your home. GSHPs are typically the most efficient type of heat pump, but installation is more complex and the initial cost is somewhat higher than for ASHPs. See more here. 

 What are the different types and configurations of heat pump systems?

There are three main options. Experienced heat pump professionals can help you compare the pros and cons of these configurations.

• Install one central heat pump (air-source or ground-source) to take the place of your existing furnace and use your existing air ducts.
• Configure a heat pump system with one or more “mini-split” heat pump units to serve one or two rooms each.
• Retain your existing furnace or boiler (if it’s not too old) and start by installing one mini-split to supply one or two rooms that are used frequently. This will provide you some experience with heat pumps, and may help when you eventually complete your heat pump system by removing your fossil fuel heating equipment — at which time you can install a central heat pump and/or multiple mini-splits, as appropriate.

Once you have an idea what general heat pump configuration you think will work best for you, dig into the following details before getting price bids:

• Be sure you are looking at “cold climate” heat pumps that will work well in Acton’s cold winter weather. Look for the highest HSPF ratings, as well as the SEER (Seasonal Energy Efficiency Ratio) rating, and ask for model numbers so you research them and get independent information. 
• If you are retaining a fossil fuel heating system (at least temporarily as a backup), make sure you get careful estimates of how much fuel will be used, and ask for a set of smart or “integrated” controls that will manage the multiple heat pump(s) and other systems (to prevent potential inefficiencies). 
• If you are not retaining your old system, ask if your new heat pump(s) will include internal electric resistance heating for the coldest hours of the winter, or whether the heat pump(s) will operate at our coldest temperatures (e.g., 0°F or below). 
• Make sure any price quotes specify that the outside compressor unit(s) will be located appropriately for air flow, elevated to protect them from snow, and kept out of the way of any dripping water or ice.