MassCEC Pilot Showcases Success of Whole Home Heat Pumps

Location: Massachusetts
Type of home: Various
When first built: Various
When last renovated: Various

Heat pumps can serve as a whole-home heating and cooling solution in Massachusetts. That was the primary takeaway of MassCEC’s Whole-Home Heat Pump Pilot, which ran from May 2019 through June 2021. And whole-home heat pumps will be fundamental to the Commonwealth meeting our goal of one million households using high-efficiency electric heating systems by 2030.

Whole-home heat pumps are essentially heat pumps that serve 100% of a building’s heating needs. While heat pumps are increasingly common in Massachusetts, many are supplementary to fossil fuel heating systems in homes. However, as the state increasingly electrifies its buildings, more and more will rely on heat pumps for all of their heating needs.

Whole-home heat pumps offer many benefits. First, they deliver a comprehensive heating and cooling solution that serves the whole house, increasing comfort and convenience. Second, they do not require homeowners to maintain and operate two separate heating systems. This eliminates the need to maintain fossil fuel pipes or tanks and keeps the homeowner from needing to maintain and potentially replace a second heating system in their home. And last, whole-home heat pumps deliver superior emissions reductions and will continue to get cleaner as the state’s electricity transitions toward being carbon free.

MassCEC’s pilot worked to demonstrate that whole-home heat pump systems offer a high-performance solution today and that the market is ready for significant expansion going forward.


Background on the Whole Home Heat Pump Pilot Program

MassCEC launched the Whole Home Heat Pump pilot shortly after ending our larger Residential Air-Source Heat Pump Program, which had run from November 2014 through March 2019 and supported the installation of air-source heat pumps at over 20,000 homes. In January 2019, Mass Save® expanded its incentives for supplemental air-source heat pumps – at least for customers switching from oil, propane, and electric resistance. This allowed MassCEC to shift its focus to demonstrating the benefits of whole home air-source heat pumps.

In order to ensure that supplemental heat pumps are being used for heating and to access their higher incentives, Mass Save® requires oil and propane customers switching to heat pumps to either install integrated controls that operate both their heat pumps and their fossil fuel system or remove their fossil fuel system. When Mass Save® launched their incentive, they discouraged the removal of the backup system due to concerns about customer comfort at the coldest temperatures, but they recently removed this language, reflecting growing acceptance of the ability of cold-climate heat pumps to serve as a stand-alone heating solution.

A major goal of MassCEC’s pilot was to demonstrate that heat pumps can be stand-alone solutions, so hopefully our pilot has helped contribute to acceptance of this approach as another option for customers along with integrated controls depending on the customer’s situation and goals. MassCEC also hoped that the pilot would surface cost-effective and efficient design strategies for whole-home air-source heat pump solutions. Some of these cost-effective projects are highlighted in the case studies below.


Awarded Funds under the Whole Home Heat Pump Pilot Program

The MassCEC pilot offered a flat incentive of $2,500 per home for existing homes that were switching from natural gas to whole-home heat pumps or new construction/gut rehab homes that had whole-home heat pumps and had no fossil fuel appliances in the home. In order not to overlap with Mass Save incentives, the MassCEC pilot was only open to residents that heated with natural gas (and were therefore not eligible for the higher Mass Save® incentives). Based on current fuel prices, customers heating with natural gas have the lowest value proposition for switching to heat pumps, but MassCEC knew that there were residents interested in making this transition, and we wanted to support these projects while gathering project data that could be used to inform future state programs and policies. The MassCEC pilot offered higher incentives for income-qualified customers and, towards the end of the pilot, MassCEC created an adder for projects that included other efficiency or electrification measures as part of the heat pump project.

In the two years that we ran the pilot, we awarded funds to 168 whole-home heat pump projects: 31 new construction projects and 137 retrofit projects (including 11 gut rehabs). About a quarter of the projects either received an income-based adder for low and moderate income homeowners or were affordable housing projects. A total of 39 installers participated in the pilot.


Lessons Learned

The primary lesson learned is that whole-home heat pumps are a feasible solution, not only for new construction, but also for retrofitting existing buildings, including older homes. See the case studies linked below for stories of homeowners who have been heating their homes with heat pumps. We surveyed pilot customers six months after project completion, and 95% of respondents were somewhat or fully satisfied with the level of comfort for heating, while all were somewhat or fully satisfied with the level of comfort for cooling. We encourage homeowners thinking about whole-home heat pumps to start with making their home as efficient as possible. Tighter homes can install smaller and/or less heat pump equipment, will be more comfortable, and will have lower operating costs. A no-cost Mass Save® Home Energy Assessment is a great place to start if you live in Mass Save® territory. Homeowners across the state can refer to MassCEC’s Weatherization Checklist.


Costs for Whole Home Heat Pump Solutions

Costs were higher than we hoped. As shown in the table below, median project costs for the pilot were $18,400. We saw less expensive costs for new construction projects versus retrofits, probably largely because new construction homes had smaller loads so they could install smaller/less heat pump equipment. Also, the heat pump equipment could be designed with the house from the beginning instead of retrofitted. For retrofits, some of the more affordable projects that we saw were for projects that could reuse existing ductwork and/or had smaller homes without a lot of small rooms. Some of those projects are described in the case studies below. Our hope is that costs for whole-home heat pumps projects will go down, as installers become more comfortable with the capabilities of heat pumps and manufacturers offer more options. However, because heat pump technology is relatively mature worldwide I do not expect to see the rapid price declines that solar photovoltaic projects have seen (although I hope I’m wrong!), so I expect that incentives will continue to be necessary to achieve the state’s electrification goals, especially for low and moderate income homeowners.

Whole-home heat pump projects can be complicated and require an installer who is comfortable with the approach. Of the retrofit projects in our pilot, 25% required an electric service upgrade, while 38% reported that their natural gas heating system also provided their domestic hot water, which meant that homeowners either had to leave their natural gas boiler in place just to heat their hot water or else buy a new hot water heater as part of the project. In the pilot, we heard many anecdotes from homeowners who were the main champions for a whole home heat pump solution and sometimes faced hesitation from installers, but our hope is that over time installers become more comfortable navigating and promoting whole-home heat pump projects. Some of the contractors participating in our pilot do have the level of experience to confidently recommend and design a whole-home approach. If you are considering a whole-home project, ask your installer about their experience and comfort with a whole-home scenario. Our Questions to Ask Your Air-Source Heat Pump Installer article has a list of questions that homeowners can ask when they are considering getting heat pumps.

In reviewing the applications, we almost never had a question about whether a system was sized adequately to heat the home; installers tend to be conservative on this front (for good reasons!). Instead, we often were pushing installers to consider sizing down equipment so that heat pump systems would not be over-sized. For ductless projects, our technical consultant (Bruce Harley), often recommended multiple outdoor units and especially single-head units (one outdoor unit connected to one indoor unit) for less cycling and more efficient operation. Sometimes, homeowners still preferred multi-head units due to lack of space for outdoor units. Ducted units can be an economical solution if a home already has ductwork, but if new ductwork needs to be built ducted projects tend to get more expensive. Compact ducted units can be a good solution for serving several small rooms.


Case Studies

MassCEC has put together profiles of several whole-home heat pump projects where the homeowner has lived with the system for at least part of a winter:

As an aside, I am putting my money where my mouth is on the issue of air-source heat pumps. At the end of last winter, my oil tank sprung a leak. It was going to be $3,000 to replace the oil tank, so that was the push my family needed to get heat pumps and remove the oil heating system. Because I was heating with oil, I was able to take advantage of the Mass Save® rebates. While I have not lived through a full winter with the heat pumps yet, it’s been great to have better cooling in the summer, and we’ve enjoyed the extra space with the oil tank removed from the basement and the radiators removed from the rooms.


Next Steps

MassCEC has the flexibility to pilot new technologies or innovative applications of technologies, like whole-home heat pumps, but we do not have the budget to scale these approaches to the mass market. So as MassCEC wraps up the Whole-Home Air-Source Heat Pump Pilot, we are excited to see what entities like Mass Save® will do to promote whole-home electrification options on a broader scale. Recently, Mass Save® has begun supporting air-to-water heat pumps and ground-source heat pumps. All signs indicate that heat pumps will be a major focus of Mass Save’s three year plan for 2022-2024. In particular, it’s great to see enhanced incentives for moderate-income households in Mass Save’s draft three year plan, since, as discussed above, whole-home heat pumps continue to have high upfront costs. For MassCEC, our next step in residential decarbonization will be launching our Decarbonization Pathways pilot. The Decarbonization Pathways pilot will build on the lessons of the Whole-Home Air-Source Heat Pump Pilot and offer more comprehensive support and coaching to homeowners and better integrate other efficiency, electrification, and renewable opportunities with heat pump projects.

Additionally, MassCEC has contributed some funding along with NYSERDA and the foundation E4TheFuture for a study that The Cadmus Group is conducting on the future of residential cold-climate air-source heat pumps. That study monitored around forty homes in Massachusetts and New York that use heat pumps as their primary or only source of heating over the last month. Results of that study are expected to be made public sometime this fall.

If you want to learn more about the Whole Home Air Source Heat Pump pilot, MassCEC published a series of blog updates on the pilot.  Reach out to us at any time at



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