Our heat pump experience


Yesterday — at our request — National Grid shut off service to our two-unit home and pulled the gas meters from our basement. We installed heat pumps last summer and they are demonstrating more than adequate capacity to heat our home in cold weather.

We are glad to be entirely free from indoor air pollution caused by gas cooking, glad to be entirely safe from the prospect of gas leaks, and glad to experiment with heat pumps — likely the principal home heating technology of the future.

By replacing our natural gas furnaces with heat pumps, we may be slightly increasing our annual spending. We are only modestly cutting our carbon foot print (more on heat pump economics here). As a legislator sharing responsibility for our climate goals, I wanted to get hands-on experience with the transition, even if the business case for the immediate change was weak.

I encourage people to start thinking about the transition and I write to share several lessons from our experience. I do not urge everyone to rush out and do what we have done. The economics don’t make sense for everyone.

This post shares my experience as a homeowner. Many of the same considerations apply in rental housing, although renters have much less control.

Your results may vary.

Each homeowner’s experience will be different. The energy characteristics of each home vary depending on their layout, their construction, and how they have been maintained and improved through the years. Additionally, different homeowners may have different energy needs — for example, empty nesters may wish to routinely heat only a portion of their home.

Our home energy journey began 25 years ago when we replaced inefficient windows and insulated the attic in our single family home in Belmont. We quickly reached the limits of energy savings that could be achieved in that brick structure without a deep reconstruction, which we could not afford.

It’s a journey.

We took a big step forward in 2009 when we downsized from that home into a two-family with my parents. With the downsizing we were able to afford a deep energy retrofit as part of a renovation of the home we bought. I’ve written about that experience at length here. At that time, we chose not to install heat pumps, but instead chose to install high-efficiency gas furnaces — a decision which, at the time, saved both costs and carbon emissions.

Heat pumps have improved dramatically over the last decade and the state climate plan has placed a higher priority on electrification. In late 2021, we decided to re-evaluate the possibility of converting to heat pumps. We started talking to contractors and the first bid we received was over $50,000. We decided we could not afford the project and put it on hold.

In March, when Mass Save came out with the new $10,000 incentive for whole home heat pumps, we decided to give the project another look. We spent several months talking with different contractors and learning from each. Over the course of those conversations our understanding of our project continued to evolve. We finally signed a contract for $33,000 (total for two units) in May 2022. Our contractor removed our furnaces and installed heat pumps in June 2022. It took us another six months to receive the rebates we were entitled to from Mass Save.

We haven’t used gas since last summer, but we waited until the rebates were straightened out before closing our National Grid accounts. With rebates from both National Grid and Belmont Light, our costs worked out to $5,000 per unit — we are a minimum cost scenario as I’ll explain below.

Don’t go it alone.

Building energy efficiency is complicated. Electrification with heat pumps is complicated. I am a do-it-your-selfer and initially assumed I would be able to learn what I needed to learn, at least to manage our efforts. Eventually I started to get a clue how little I knew.

For our energy efficiency retrofit in 2009, we were very fortunate to find a general contractor for whom efficiency was a life mission. He understood the available technologies and the tests to be done to measure quality. He also had relationships with building science specialists who advised on the most difficult technical choices. He was able to get us into National Grid’s deep energy retrofit pilot program and National Grid brought in additional supervisory expertise as well as financial assistance.

It’s not necessary to go as far as we did — the maximal insulation measures we that took turn out to have very low payback. At a bare minimum, people ready to move on efficiency improvements should start with a Mass Save audit, take their suggestions, and accept their support for efficiency projects.

When we turned to installing heat pumps, we were again fortunate to find helpful expertise. Belmont Light requires people seeking heat pump rebates to work with their electrification consultant. Belmont’s electrification consultant was terribly helpful in re-thinking the size and type of heat pumps which we needed to install in our home. They worked through the engineering data for our home, asked a number of questions that we did not know to ask, and led us ultimately to a better pump choice which none of our contractors were initially offering.

Belmont and Cambridge offer free energy consulting services, but if your community does not — I’m not aware of comparable services in Watertown or Boston — it’s well worth paying up front for help in sorting out the options.

Insulate first.

Experts always advise that people should do as much insulation and air-sealing as they can afford before installing heat pumps. We unwittingly followed that advice by doing our big energy retrofit project in 2009, long before we installed heat pumps. When Mass Save came last April to do their mandatory pre-installation audit for our heat pump project, they had no recommendations for further efficiency improvements.

Good insulation means less overall heat loss which means less demand for heating — one can install a smaller heat pump. Good insulation also means fewer spots in the home that are especially cold. A powerful oil or gas furnace can quickly blast heat into the especially leaky and cold spots of a poorly-insulated house. Properly-sized heat pumps generate less heat, but run more consistently than fossil furnaces. A central heat pump may have more trouble reaching poorly insulated spots and one may need additional heat pump heads located in cold spots. More heads mean higher installation costs, higher operating costs, and more management of the system by the homeowner.

In our own case, after the insulation work we had done, all we needed was two small heat pumps — one servicing the ducts in each unit — and both units feel evenly heated on the coldest days. We can “set it and forget it.”

Good insulation makes homes more resilient. If we lost our heat for a week in the winter, our home would remain relatively comfortable. (Note that going electric does not increase one’s vulnerability to power outages — most fossil furnaces require electrical power to operate anyway.)

Mass Save supports basic energy savings work that can be done at any point. Deeper efficiency work needs to be coordinated with major home maintenance like exterior siding replacement.

Do it for the right reasons

There many good reasons to do home energy-efficiency work (the first step towards electrification):

  • Generally increased temperature stability in both winter and summer;
  • Elimination of cold spots in the home (or hot spots in the summer);
  • Improved indoor air quality (with installed ventilation and filtration);
  • Reduced heating and cooling costs;
  • Reduced vulnerability to fossil fuel price volatility;
  • Resilience in power outages;
  • Immediate, often-substantial, emissions reductions.

There are also good reasons to go the next step and electrify:

  • Improved indoor air quality by eliminating gas cooking;
  • Safety benefits from elimination of flammable fuel in the house;
  • Modest immediate emissions reductions;
  • Potential for much greater emissions reductions if the grid gets greener as planned;
  • Support for a technology that is critical to the Commonwealth’s long term climate goals.

Cost reductions and price volatility reductions are not among the reasons to electrify. Even when converting from dirty oil furnaces, the economics are uncertain; a furnace upgrade may be cheaper on a total return basis. More on heat pump economics here.

For me, it also feels good to think, that through efficiency and electrification, I’m contributing just a little less to the world demand for natural gas that supports the Russian war machine in the Ukraine. Of course, as long as natural gas power generators serve winter needs, we are still contributing substantially to that demand.

Do it right

An unprofessionally insulated home may remain inefficient. A poorly designed heat pump installation may not deliver comfort and may be costly. A heat pump may leak refrigerant, operate inefficiently, and contribute to global warming. See this later post on our mixed first season result.

While one does not need to go to extremes with insulation projects, take the time to be sure you have a good plan and good people in place to help you.

Measure the results

Things can go wrong even in the best installations. It’s a good idea to put in place a home energy monitor so you can see where your electricity is going.

For several years we had wondered why our electric bills were higher than expected. When we recently installed a monitor to measure our heat pump load, we identified a huge intermittent load which turned out to be our backup hot water heater. We realized that our solar hot water heater was not working. We had not regularly maintained it and it probably hadn’t been working for years.

Using tools that allow you to monitor your heat pump energy consumption will give you comfort that your pumps are properly installed.


Honestly, none — we have been fortunate.

See this later post on our disappointing first season heat pump results.

Whether or not they have had short-run financial payback, all of our projects have given us important benefits and valuable understanding. We are grateful to the professionals who have taught us so much.

Update: Deep cold experience

In the recent polar air event (February 3-4), we got the chance to test our new pumps down to about -8F with heavy winds.

The pump system did continue providing hot air heat through the coldest depth of the night.  It is possible that the hot air was a little less warm than normal, but not distinctly so.

As to overall temperature in the house, the pumps did basically keep up.  Because of our deep insulation, we have installed relatively small pumps:  We have one 1.5 ton pump for each unit in our two family.  While our exterior insulation is very good, heat does tend to rise from the lower floors to the top.

During the most recent event, because of second-floor thermostat settings, the upper unit’s pump was off until after midnight, and the lower unit’s pump was carrying both units.  As a result, although the attic remained in the high 60s, the first floor temperature sagged to 62, three degrees below the first-floor thermostat set point of 65.  (This may have been due to a later discovered leak.) After the upstairs unit’s pump came on (and we tweaked a higher-than-normal external ventilation setting), the first floor temperature stabilized. After sunrise, the first floor temperature started to rise, even though the outdoor temperature was still -5F.  Temperatures had caught up to the day thermostat settings in both units by late-morning when the outdoor temperature was still near zero.

In summary, the recent experience suggests that we can count on our pumps to keep us comfortable without any adjustments down to zero F or a little below.  As we get towards -10F we need to be more careful about our thermostat and ventilator settings, but can expect to sustain comfortable temperatures.

Return to heat pump outline

Published by Will Brownsberger

Will Brownsberger is State Senator from the Second Suffolk and Middlesex District.

74 replies on “Our heat pump experience”

  1. Thank you for sharing this, Will. I rent and my landlord tends to scoff at eco-friendly suggestions, so I don’t think it will happen for me, but I’m glad you were able to make this modification. Do you have a generator in case you lose power for more than a few days in winter?

  2. Will, this is very interesting. Can you please clarify a few points. 1) it seems like you got $23,000 in incentives (quote was $33K and your cost was $5K for each unit), is that level of rebate generally available? 2) how large an electric service do you have and what was the cost of the upgrade. 3) what do you do for air conditioning?

    1. $10,000 per unit rebate from Mass Save. $1,500 per unit rebate from Belmont Light. Those are the currently available incentives for whole home conversions (old fossil fuel system removed or no longer used).

      We have one 100 amp service for each unit. We replaced the electrical systems in 2009-10 and did not need to make any further upgrades for our relatively small (1.5 ton) heat pumps.

      The heat pumps provide both heating and air conditioning and replace both our gas furnaces and our outdoor A/C compressors.

  3. What was your existing heat distribution system, Will? Water or air? If the former, what was its fate?

    1. Our pre-existing heating system was a natural gas furnace with ducted hot air. The ducts also served cold air in summer. That system dated to our full renovation in 2009-10 when we removed old oil burners, oil tanks, chimneys, and radiators. At that time, we installed ducts in the basement for the first floor and in the attic for the second floor. We were able to re-use that duct work for the heat pumps — our HVAC installer was able to mate the new heat pump air handlers for each unit into the ducts where the hold furnace air handlers were.

      1. So Will has a ducted system, which took advantage of the existing ductwork. We have a ductless system, because our existing system was hydronic (forced hot water through radiators). Ductless systems are much more common. Wall units are mounted typically on exterior walls and direct air into the interior rooms, but they are still relatively straightforward to install. We did ours several years ago, and the entire cost was $20k (two systems), minus $5k in rebates. We haven’t used our gas boiler the past two winters. The thing to watch out for is placement of the wall units, since there is not one in every room. We have two downstairs, two upstairs, and one in the basement which is a ceiling unit fit between exposed joists. Without the boiler going in the basement it got extremely cold so we added the second heat pump after the first winter. We have a single 100A service feeding both systems. The heat pumps typically draw 10 to 15 Amps combined, sometimes almost 0 on milder days.

        1. Sounds like you’re planning to keep the radiators & maybe the black iron piping in place, then, Darrell?

          Given the installed base of hydronic systems (my two-pipe HW system dates from 1926 and is in perfect shape) in towns roundabout, it would be nice if we could encourage an alternative to gas & oil that could make use of some of it. Steam systems, especially one-pipe, I dunno.

          1. We left our hydronic system in place as a backup and fire it up once a year to make sure it still works. We haven’t used it the past two winters. Air-to-water heat pump systems ‘may’ be coming, but the problem is that heat pumps can’t heat water hot enough for large radiators. So if you were willing to replace the cast irons for thin, lighter wall-mounted radiators, like those in Europe and Japan, you might be able to use the existing piping system combined with a heat pump. That’s a lot of ifs. It would do a better job of distributing the heat around the house, but you could not use it for A/C in the summer, a real advantage for air-to-air heat pumps. It would also be a no-go for steam systems due to having single pipe feeds.

            1. Yep, and I doubt if air-to-water will ever be efficient enough to use with my cast-iron radiators, which I love–nice, even heat everywhere. I was thinking more of ground-source systems, especially the “neighborhood” approach that could even re=use the gas piping in the street. Not the lowest-hanging fruit, perhaps, but it worries me that by prescribing air-t0-air heat pumps we’re in effect discouraging the development and investment in other kinds. Rebates & subsidies, I think, should be based on performance criteria, not on a particular technology.

  4. Hi Will, Just to expand on Melanie’s question – what is the amperage draw when your system is heating? Belmont Light doesn’t tend to go down as often as the commercial grid, but I imagine a generator that can handle that load might be expensive…

    1. According to our power monitors, the maximum heat pump load averaged for a 15 minute interval in the last 60 days was 3258w in the upper unit and 3113w in the lower unit. The maximum load that either pump achieved in any 1 minute interval over the past seven days was 3438w. The pumps are on 220v circuits, so that max wattage equates to a 15.6 amp draw. The pumps are variable speed and often draw less.

      The maximum one minute load over the last seven days on our electric range was 5307w and 4674 watts on our hot water heater. So, the heat pumps are not a bigger short term load than the other major electrical appliances. They do run more, so over the past 60 days they are the largest component of power use — 26% in the upstairs unit; 41% in the lower unit.

      1. Typical water heaters draw a maximum of 7.2kW, or 30A @ 240Vac. So that is indeed less than the heat pumps.

  5. Congratulations on your new heat pumps. It is important to understand that Belmont has a municipal electric system which is about half the cost of electricity from National Grid. As a HVAC engineer I can safely say you need a backup source of heat which your system has ( electric heaters) a secondary source of heat can be natural gas (oil too) . The next consideration needs to be your electrical system- most of the homes in the Boston area are approaching 100 years plus with the electric system about 50 years old with parts even older so in addition to upgrading the hvac system you may be facing a total electrical upgrade- so on this note Will is there a rebate or tax credit that will help cover these costs as well ?

    Please do not get me wrong I believe in more efficient heating and cooling like the insulation there may be other expenses as well. Also just a note make sure there is a fresh air exchange on any new system you install

    1. Yes. Municipal power is much cheaper right now.

      The new federal legislation includes electrical upgrade incentives. I’ll post more on the federal incentives soon.

      We did have an energy recovery ventilator installed for each unit in 2009-10 — they bring in plenty of filtered outside air without much energy loss.

      To be clear, our only heat source is the heat pumps — we do not feel the need for back up electrical resistance heat.

      1. Belmont electricity was way cheaper when I lived there in the 1990s. I think it is always cheaper because it is not making money for shareholders, right? I believe we need to change to more local generation if we are going to go all in electric.

    1. There is no financial payback — it is a net cost. We expect a slight operating cost increase which will be offset by our savings from yanking the service so there is no monthly minimum charge anymore. The annual cost impact is close to zero and we have a $5,000 net upfront cost for each unit. If one assigns an adequately high social cost of carbon, one can, depending on all assumptions, achieve a benefit-cost ratio > 1. See this post for additional discussion.

  6. This is incredibly honest and valuable. I learned a LOT from this—and I know more than most. What I think is needed is a consumer advocacy group, statewide that could direct those who can manage these improvements and connect people to the incentives that are out there. This could help us work toward a grassroots answer to climate change and empower all citizens to contribute to the solution.

    1. As someone in the Museum field I read this post and the comments with great interest. My museum colleagues across New England are also looking for collegial resources like what you described to help guide the process of shifting their buildings to greener options!

  7. Thank you Will, most informative. The more real world experiences with heat pumps we can refer to the better. There is no one solution that is best for every building at any one time, but the move to heat pumps over the next 20 years should be consistent and ineluctable. Coincidentally on Jan 4 the DPU is holding a public hearing on National Grid’s latest 5 year program for its gas deliveries. In this filing National Grid is demonstrating (and confirming) its indifference to trying to be compatible with the Commonwealth’s targets for reducing emissions. It includes a scenario for heat pumps which reads like a manual from 2005. The percentage of misinformation – explicit and implicit – in National Grid’s messaging is exceeded only in Congressman -elect George Santos’ biography. Unfortunately National Grid itself cannot be trusted in this context, not surprisingly because it has a vested interest in selling as much gas to as many customers for as long as possible regardless of the consequences for our climate or our pocketbooks.In contrast I recommend a recent webinar on Cold Climate heat pumps which includes a wealth of information and practical advice, including from northern Maine – “Cold Climate Heat Pumps – Warm homes on the coldest days,” at https://www.youtube.com/watch?v=OcwIz6heDss. I note also that the countries with the highest household penetrations of heat pumps are Norway (60%), Sweden (43%) and Finland (41%) none of which are known for their mild winters.

    Happy New Year and all hands to the pumps.

    1. Nicely put–chuckled aloud at your description of National Grid’s lack of integrity in this scenario. Well done!

    2. Totally aside from this, I just hope George Santos is lying about his last name along with everything else!

      I’m really hanging this off Martyn’s comment just because of the George Santos reference, maybe it should be a standalone comment, but anyway I live on the first floor of a two-family in Harvard Lawn. There are hundreds of similar houses built at about the same time (ours was in 1926, according to a furnace permit we found in the basement. Or maybe that was when it was converted from coal to oil?)

      The landlords renovated their apartment upstairs, including converting the third floor to living space (there was one bedroom up there originally), totally insulated the roof and part of the second floor, and replaced all the windows about 20 years ago, but my apartment had the original drafty windows and (I suspect) literally no insulation in the walls.) Last spring, they replaced all my windows with very good, tight-fitting, insulated and coated windows and all the drafts are gone! (It will be a couple of months of gas bills before I can be sure how effective the new windows are at reducing heating costs, but it’s much more comfortable inside.)

      I have two-pipe steam heat and upstairs has forced hot water. Both systems are very common in the northeast. Is there a heat-pump system that works without retrofitting ductwork into the walls or mounting split units in various rooms and totally removing the existing heating systems?

      Thermodynamically, a heat pump extracts energy from the environment and uses it to produce very hot working fluid on the hot side. Physically, that hot fluid can be used to warm air and I don’t see any reason why it couldn’t equally as well produce hot water, but for steam, it would have to be above the boiling point of water, which might be problematic. Do such systems exist? Are they more or less efficient than the conventional hot air systems? Do they work in a cooling mode in the summer?

      First, though, I suspect it would be more worthwhile to upgrade the insulation (blow-in cellulose or expanding foam or some other method), rather than worry about heat pumps at this stage of things. Any comments from people who have done this?

      P.S. while very informative, the webinar that Martyn linked to did not really address either of these questions. As to whether to invest first in a heat pump system or better insulation, they basically said “it depends” and to do a detailed analysis of your individual situation. They didn’t address the particular existing heating system questions at all, except to say a central heat pump works very well with minimal changes when installed in a home with forced hot air heat.

      1. See my comments above to David Lynch. Right now heat pumps top out at around 140 degF, which is why they work for hybrid domestic water heaters. But that won’t cut it for large cast iron radiators, and not even close to making steam. They wouldn’t cool your house either; radiators ‘radiate’ heat, but wouldn’t absorb it very well. Perhaps a strong blower behind a ‘cold’ radiator would do the trick, but I wouldn’t count on it. Definitely insulate first, because heat pumps get their efficiency (3 times more efficient than baseboard electric or radiant resistive heating) from operating ‘at the margins’, providing just enough heat for the enclosed space. As the delta T grows (the difference between outdoor and indoor temperature) or is thwarted by poor insulation, heat pumps become less and less efficient. So insulate and eliminate drafts first or you will overspend on a larger system than necessary.

    3. There is no need to speak/write of National Grid derisively. The company is critically important to our state’s (and beyond) economy and overall well-being. Millions of people depend on it. To cast it as enemy is short-sighted. The accusation of mis-information should be supported – otherwise it’s not credible coming from someone whose objectives appear to be in conflict with National Grid, or those of us who want natural gas and electricity costs to remain affordable.

  8. Will, thank you for telling us about your experience. I am not a fan of super insulated houses. We have insulated the attics and installed energy efficient windows in our home (Watertown) and a 2 family rental (Belmont). That’s all we want to do. Things like radon gas (and who knows what else) can be trapped in these super insulated houses. I know there are ways to vent radon gas. That’s another cost to consider when insulating a house to the max.

    1. My wife and I are fresh air people too. In the shoulder seasons, we open the windows like everyone else. When we are heating and cooling our mechanical ventilation can gives us more than enough outside air without as much energy loss.

    2. I feel the same way. We also invested in efficient windows and good insulation in the attic, but have no desire to make the house super-tight. The air quality is extremely important to me. Will, who lives in an extremely well insulated house, mentioned that if there is power failure, he and his family could last for a week. I’m not so sure. It would be like living in a plastic box – the air would become stale, so it would be necessary to open some windows for ventilation, which would impact the temperature inside.

      By the way, this reminds me of an elderly aunt of mine who recently passed away. She grew up in the countryside where everybody lived in old wooden houses, but later in life she moved to a city and lived in tight apartments. She once told me that she thought that slightly drafty wooden houses were much healthier than tight apartments in terms of air quality. I think she was right.

  9. Once again, thank you Senator for this most interesting and helpful-useful information!! This is incredibly insightful and helpful towards utilising this capability!!

    BIG thank you, and best wishes for the 2023 New Year.
    Thank you for your advocacy, support and reach-outs!!

  10. Thanks Will! Compelling and understandable snapshot of a complex undertaking. We are thinking about our options with a full conversion and this is helpful.
    Sandra Fay Richard

  11. There are a lot of expenses not covered like a new electric stove, electric hot water heater, clothes dryer.
    Maybe 5 to 10K on these items. Then there is the empty chimneys to decide on.
    I would love to see new house siding panel choices that would replace the clapboard / vinyl types we currently have to chose from. Also a central web location to direct consumers to.

    1. A new electric range (or cooktop) should be induction, as opposed to ceramic glass alone. We got one recently and are extremely happy, as they are both more energy efficient and high performance. The glass doesn’t get hot (well, a little), the pots and pans do, and heat up very quickly. Performance is very similar to gas. The oven within a range is also more high end.

  12. Also – what if electricity was generated locally with gas?
    It seems a lot of energy is lost in the transportation of electricity. What if there were efficient small electrical generators?
    Thanks for all this effort to keep us informed and thinking about it.

    1. Burning gas in a local generator is still burning gas, which we need to get away from. Electricity can be generated in many ways other than gas; e.g., hydroelectric, solar, wind, tidal, geothermal. Most of these methods are much more efficient in specific locations; any lossage in transmission balances against not having to pay for fuel.

  13. Will, when we investigated a few years ago, mass save benefits weren’t available to belmont light customers who had no natural gas connection. Is that still the case? If it is, why doesn’t belmont light participate?

    1. My understanding is that you still need to be a National Grid customer to get the incentives from Mass Save if you get your power from Belmont Light or another municipal utility.

      Municipal participation in Mass Save is a long political story — basically municipal light utilities across the state have preferred to run their own show. Mass Save adds about two cents to rates for the major utilities.

  14. I hate to be negative here but I dont get the rush to alternative energies at such breakneck speed. Jan 1 starts new federal taxation policies on gas, coal and oil. I agree we need to move to a better situation but killing gas, oil and coal will hurt us all and our economy. I have a heat pump as part of my A/C and it is just OK, it cost a fortune, my electric bills are outrageous.

    1. We’re moving away from burning hydrocarbons because they increase global warming. Note that your high electricity bills recently are probably due to what your utility pays for natural gas, where markets have gone crazy; alternate energy sources don’t need fuel, so they can’t be affected by would-be tsars.

    2. Thank you, Rick, for a much needed dose of common sense. People in our state need uncomplicated and AFFORDABLE heating/cooling solutions. The cost of electricity will continue to be rising – primarily due to the heavy pressure on the industry to convert to renewables (which doesn’t even guarantee reliability) – and those rising costs will be passed on to consumers, and likely become crushing to low-income and regular people. Ballooning energy costs will also increase the costs of goods and services (including food). It is very irresponsible to agitate for (or implement) policies that eliminate choices and don’t prevent, or at least effectively mitigate negative impacts.

  15. Will thank you for sharing your experience with the heat pumps. My wife and I appreciate how you communicate with your constituents – no one is better at it than you. Hope you and your family have a great holiday.

  16. Did you consider rooftop solar to generate the electricity required by the heat pumps? If so, what were the pros and cons, and how did the economics work out?

    I’m considering beginning a heat pump journey; we currently use an in-ground propane tank and forced air. We already have rooftop solar and roughly generate what we consume over a year. We have another half of the roof that we could install a second solar system on for heat pumps, if it made sense.

    1. Your propane/ducted heat system may be a great candidate for replacement with heat pump. Give it some thought.

      We did solar 11 years ago and the incentives paid it back within that period. Now and for the next 20 years or so we are continuing to enjoy several hundred kwh per month of generation. It peaks mid-day, so it doesn’t directly offset heat pump power demand, but it helps the bottom line.

    2. Nobody seems to be considering what will be happening to millions of solar panels when they reach the end of their lifespans, which is 15-20 years. They cannot be recycled and have environmentally harmful elements in them.

      Also, installing solar panels on the front of the house is in my opinion an esthetic abomination.

      1. There are solar panels 40 years old and older, still producing at 80% of their original output (1/2% loss per year is typical). Our neighbors love how our panels look (12 years old and going strong), and they’re right on the street. We’ve filled the entire front section since we got heat pumps and an EV. We self-produce about 2/3 of what we use, with a fairly small roof.

        1. Glad you could do it, and that you and your neighbors are happy with it. I could not do it – it would be sacreligious to a grand old house with a complicated steep roof with multiple gables (not to mention damage to the slates). Regarding disposing of solar panels in an environmentally acceptable way, there is no way to do it. As they become more ubiquious, it will be a major problem sooner or later.

  17. Hi Will,
    So we are about to make a decision and got a few estimates, but wonder if you have someone you particularly recommend? We have oil heat so do not qualify for MASS Save rebate. Also, we are starting with half the house this time, and may do a second unit in future. As far as I can tell, rebate from Belmont Light will be about $1,500.00 – 2,000.00. Did you do ductless? Mitsubishi or other for the heads?

    1. Hi All,
      I have just completed installation of a heat pump system (with 5 indoor wall hung units) one outdoor Mitsubishi unit, installation by Muirfield Mechanical Services. The house was already well insulated. Because the house has brick siding with an old uneven albeit attractive pattern the cost was quite high (just around 27,000, with the 10,000. rebate and 1,225. via Belmont Light). I have kept the gas furnace with forced hot water as back up to see how the new heat pump system works this first year. Also I have still to replace the gas water heater and gas cook top. Everything else is electric. MASS SAVE has not sent the rebate, disappointing to wait way beyond the 4-6 weeks promised!

    2. Muirfield Mechanical in Ayer, ask for Jeff. Get several quotes from experienced installers. Ductless unless you have existing ductwork. Mitsubishi, Fujitsu, Panasonic are all good.

  18. Thank you, Will, for sharing your experience–and describing it in such a well organized and lucid manner.

    We also installed heat pumps in the fall of 2019 and I will add our experience to your thread:

    We live in a 1860’s town house in Boston. We are ‘insulated’ on each side by other town houses but our back and front brick walls are the original lathe and plaster without any room for insulation whatsoever and shockingly cold in the winter.

    The house was converted to a three family in the mid 50’s and we live on the top three floors and rent the bottom two. The original heating system was a gas furnace, forced hot air with a single thermostat. We paid for all the heat in the building. The gas furnace was probably 50-60 years old when it started to fail and that prompted our decision to convert to heat pumps. Since the tenants had moved in with the understanding that ‘heat was included,’ and since we were connecting each unit to its own electric meter we told them that we would pay the extra cost of electricity attributable to this new arrangement. Whether out of kindness or gratitude for the new system that gave them total control over the heat and air-conditioning, neither of the tenants took us up on that offer.

    It has been three years now since we did the installation. The system works well, although we do supplement it with a small oil-filled radiator plug in heater in the dining room, which is a bit to chilly for us. (My guess is that using that sort of small supplemental heat is a lot cheaper than maintaining an entire back up system.) We also like having the flexibility of a heat pump system with multiple mini-splits which we can turn on or leave off as we use different rooms. (Even on the coldest or hottest day, it takes one of the mini splits only 5-10 minutes to make a room perfectly comfortable)

    While the installation over three units in an old building was complicated and costly, I estimated that in our unit we are saving money on heat–about $800 the first year and $500 the second–compared to the days of the gas furnace. We also enjoy the added comfort, the ability to zone the system,, and the air conditioning, which we use sparingly and only had before with the tedious installation of heavy window units.

    Your comments on the different characteristics of different houses with regard to heating needs, and on the importance of getting good professional advice in the planning stages are on the mark. I would only add this thought. Most long term homeowners are likely to face a heat system replacement of some sort. Now is a good time to consider heat pumps as that eventual replacement and to plan–logistically and financially–for that eventuality. Logistically, what one can do right now is to insulate and weatherize the house in any way that is reasonable and makes financial sense.

  19. Thank you, Senator, for sharing your experiences with your conversion to heat pumps. I do hope if we have a snowed-in situation like just happened in Buffalo, NY where some people froze to death in their homes, you and your family have the needed heat for a week as you say. Given what I read about the Buffalo snowstorm, I can see the value in having a gas stove because it can be lighted with just a match when the electricity goes out. Survival is more important to me than long time climate goals. Just wondering do the heat pumps have a big thing outside the house (sorry don’t know the terminology) which someone could steal for copper or whatever? I’m also glad to read you’re in proximity to your parents so mutual time will be spent together. I know. I lost my parents and there’s nothing more important than time in the end. Speaking of time, my lifespan may be short so I might not go into this expense. The houses turned over (sold) near Boston College are gutted and turned into non-owner occupied student dorms so there’s little incentive to do improvements, all thanks to the Boston building department decision what this area is good for. Highest but not the best use.

  20. Will — what did your supplier claim was the working temperature range of your heat pumps? We bought for our house in Brighton during the 2013-2014 Boston-sponsored frenzy, and found too late that the units we were sold started to become inefficient at ~15F and were useless below 5F — not a common temperature this close to the ocean but not uncommon. (Those are outdoor temperature; it doesn’t matter how well the house is insulated, the heat exchanger just doesn’t exchange.) At the time a northern-NewEngland columnist mentioned units that kept them warm in worse but that didn’t do AC. I get the impression the tech has improved since then, but haven’t investigated.
    Also — wrt a number of comments about ventilation — did you look at heat-exchanging ventilators to provide a dash of fresh air? I’ve read of counterflow units (indoor and outdoor air moving opposite directions in 2 ducts in contact with each other, so the air that comes out of the indoor end is almost as warm as the air going into the outbound end), but haven’t looked at whether they’re now available for home use.

    1. Our heat pumps are both Daikin RZQ18TAVJUA which are tested to maintain their capacity down to 4 below zero. So far, we’ve seen them at 12 above and they had plenty of unused capacity (off-time and power-use below max).

      Yes, we have energy recovery ventilators. They work well. We have plenty of fresh filtered out door air, even in the heating and cooling seasons. Two boxes each feeding into the heating/cooling duct system for each unit. They are quiet and have remained trouble free for 11 years now (filter replacements required).

    2. Sounds like the HP units you were sold were “standard” rather then “cold-climate” units. According to the webinar posted by Martyn Roetter above, the standard units start losing heating ability below 47F, and bottom out in the 20s (if I remember the graphs correctly), but the cold-climate models lose very little efficacy even at -5F and some as low as -15F before that become less capable of heating. Standard units are cheaper and are fine farther south (e.g. in Maryland or Virginia), and good insulation helps ride out cold nights or short cold snaps, but I think in Massachusetts we shouldn’t consider anything but cold-climate models.
      The cold-climate units cost more, for several reasons. They have beefier compressors, fans and plumbing, and the manufacturers tend to include cold-limate capabilities as high-end features, only in their more expensive models, so you would probably be paying for features you don’t really want or need. I don’t think the installation costs should be any different.

      Yes, the tech has improved as well. I think the current cold-climate models (at least, the ducted models) all do A/C, but maybe that’s an optional feature or has changed in the last 7-8 years.

  21. Because the Feds are giving a $10,000 and Belmont power $1,200 towards heat pumps.
    This has driven the cost up. I would assume it would be cheaper without this subsidy.

  22. Congratulations on using taxpayer dollars to transition from heating with gas to heating with gas.( And now some coal as well.)

    Massachusetts has the highest electrical rates in the nation but we can’t even keep the lights on during a one-day rainstorm. Maybe if we want to save on energy we could stop building 34-story bio labs instead of pretending our grid and generation capacity can support these luxury fantasies.

  23. This is our first winter with our ductless mini-spilt heat pumps. We continue to need our legacy fossil fuel heating system (oil — circa 2010 upgrade and very efficient) for very cold mornings and days. The six minisplits are not in the bathrooms, kitchen, basement room, one bedroom, and hallways due to configuration of the house and costs — and the rooms without the minisplits get cold. Our consultant told us we would need to keep the legacy heating system during winter.
    We know we will not recoup the cost of the minisplits (approx $30,000 before the $5,000 rebate). I’ve started a spreadsheet to track costs of this heating season compared to previous heating systems. I wonder if a switch to biofuel for the legacy system is the next step for us.

  24. Will Thanks so much for the very informative article. Also appreciate all the questions and comments that others have made. I have just contacted the Cambridge consultant, Abode.
    After we talk with them we may have more thought or questions for you.

    Joe and Genevieve Coyle

  25. Will, thanks for sharing your experience. I’d be interested in knowing how you went about finding contractors to talk with.

    1. Mass Save does have a list of heat pump installers who have met certain criteria. As I recall, we started from that list and just worked the phones, email, and the web to identify a half dozen who were reasonably local and apparently qualified. It’s good to solicit proposals from several and check them out — using your consultant/coach to help you ask the right questions. You are simultaneously deciding whom you want to trust and also what design approach you want to take.

  26. I installed heat pumps in 2022 and was led to believe I could get a rebate without tying in the pumps to my oil heat system. MassSave denied any rebate at all which did not seem like the proper way to incentivize. The installation costs were significant. The electric bill is too high to rely solely on the pumps. I wonder if I am eligible for any state or federal tax credits.

    1. You should probably push back by calling Mass Save. The company that they use to process rebate requests seems to err on the side of denying valid claims. If you’ve done that already., let me know and I’d like to hear more about exactly what happened for you.

      1. Yes, thank you, I pushed back in writing and on the phone. No rebate of any size if the heat pump system is not tied in to the original heat system, in my case oil, called integrated control. It is cost prohibitive now to add the tie-in. The MassSave denial letter was a pre-printed form with lack of integrated control as a reason for denial. It is too bad there are not graduated levels of rebate to provide incentives.

  27. As a Belmont resident, I would like to share my (frustrating and eventually fruitless) experience on trying to get the rebates on heat pump installation, and would like to see if there is anything you can do to help owner who self-install their heat pumps (i.e. DIY). Two main differences, compared to your situation, are

    – We have oil-based system, and so as Belmont residents who are not National Grid customers, we are not eligible for MassSave rebates. There is a local rebate through a Abode, a program that the town joined, which is much smaller ($700 per 12000 BTU), if one is lucky enough to get it. We did not in this case as explained below.

    – We decided to do the installation ourselves, using a DIY system. This is after getting several quotes where labor cost consistently works out to around $2000 per person per day. To install a system where the heat pumps themselves may cost $2000 and the labor is $5000, we ourselves couldn’t afford it. It is not a complaint, just to say that there exist DIY options for homeowners who want to save money

    To qualify for the Belmont local rebate, we first had to go through a pre-qualifying process where we specified the system we decide to install. We used a DIY brand called Mr. Cool, which is popular and being sold through many retailers including Costco. Several of their units are qualified on the Abode (i.e. Belmont rebate local program) website, so our pre-qualification was approved. I bought the heat pumps, stands, some tools and extra hardware, and it took about 3 days to install and tidied things up. We got it up and running during the hottest days of the summer, the first week of August, quiet, cool and pleasant.

    Now getting to the hard part of getting the $700 rebate on the 12K BTU system we installed. As required, we sent receipts, picture of installation with insulated ducts, wiring, etc. to
    Abode Energy Management for post-install review, and they approved the installation. Abode then forwarded this whole application Energy New England (ENE), which seems to be running their own approval process again. They first verified our account with Belmont Light, which is in good standing. But then, ENE came back with this response, quoted in verbatim

    “To be eligible for this rebate, heat pump installations must be completed by an experienced and licensed professional. As this was a self-install, we require proof of licensure in order to proceed with your application.”

    Now of course I am not a contractor and therefore not having the licensure they demanded. But then one can see how this circular system of rebates are supposed to work:

    – Home owner *must* use a contractor to get a rebate
    – Contractors, seeing that there are rebates in the system, increase their installation price accordingly.
    – Homeowners who opted in to DIY their heat pump, are mislead to believe that they can get a rebate. There is no where in the belmont light website which said that a contractor must be use. In fact the Adobe pre-qualification process included many DIY heat pumps, which are designed for the owner to self-install.
    – Rebates are effectively paid straight to HVAC contractors. Anyone who installed their own system, to reduce their carbon footprint, are excluded in this process

    So after two “successful” pre- and post- installation approval, and good energy customer account qualification, we are effectively stopped from getting the rebate because we did not hire a contractor to install our heat pump. I would like to see if you have a process where we make our local governments/Abode/Energy New England to clarify their stance on rebates for homeowners who self install the heat pumps. We would probably install heat pumps nonetheless, but it is not fair to discriminate against DIY installers. Although I also suspect that migh as well be the intention of the incentives in the first place.

    Thank you

    1. First, congratulations on being such a competent DIY! Hats off — respect from one DIY to another.

      You are right that the implied labor costs are high — although I think much of that is overhead: The contractors have to support sales people and engineers who go out and spec multiple jobs and don’t get them all.

      As to the rebates being limited to qualified licensed installers, I’m not sure that is wrong: Installing heat pumps properly so they don’t leak refrigerant — and do more harm than good — does require special training and skills. You are apparently on the very high end of the DIY ability scale and your installation may be better than what the professionals would do. But I’m not sure that should be our assumption for policy purposes.

      You raise an important issue and I’d like to hear more views on it.

  28. Will,
    I’m moving forward on using my house as a zero net carbon demonstration home. It will have a combination of solar and B100 Biofuel for electricity demand, heat and hot water. The solar is financed by Sunnova and requires no money down. There will be a net savings on electricity as the system will overproduce a bit, and I’ll also make some return on RECs for the excess power. In short the reduction in electricity will more than pay for the monthly payment to Sunnova. My current Buderus Boiler will, with small modification, be able to handle the 100% Biofuel. No expensive equipment or compromise in performance or comfort required. Given the much more reasonable cost to get to the same end result, why is the state not giving consideration to other options besides “electrify everything”? Given your experience is it any wonder that adoption rates are low? Now, with energy prices returning to levels lower than the Russian invasion of Ukraine, I suspect adoption rates will be further impacted. Hope to get your thoughtful consideration on this point.

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