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.
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.
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.