Mixed heat pump results

This post reports poor efficiency results in our first full season of use, 2022-3. These poor results were due to refrigerant leaks. See improved results with leaks fixed in 2023-4. See also revised analysis for 2022-3 here. The conclusion of this post stands — that the leaks make the installation a net negative — both environmentally and financially — for the first few years at least.

I know many who are happy with their heat pumps. And many studies show better average results than we have achieved.

But I do feel an obligation to share my family’s mixed results since I’ve told a positive story so far.

We’ve been very comfortable, even on the coldest days. But now that we’ve been through a heating season, we can do an efficiency comparison for our heat pumps. The results are disappointing — so far the pumps have been so inefficient that the climate would be better off if we had stayed on gas heat.

And that conclusion does not reflect the additional fact that one of the two heat pumps in our home leaked four pounds of refrigerant. Between the inefficiency and the leak, the net climate effect of our heat pump conversion has so far been about the same as putting a typical car on the road for a year.

We knew enough not to expect cost-savings, but we were hoping to benefit the environment. When one converts to an electric heating system, one expects gas or oil bills to go down and electricity bills to go up. Because we were able to fully disconnect from gas, we also saved the monthly gas connection fee; that helped keep the otherwise-disappointing net cost change to essentially zero. If gas prices had not been so high this season, we might have seen an overall increase.

What surprised us was the way the climate numbers worked out. Both the cost and the greenhouse gas impact of a heat pump conversion depend on how efficient the pump is in moving heat. As it turned out, our heat pumps were only about 150% efficient, [see revision here] although they were rated 278% efficient. That means that they needed more power to run and demanded more output from the gas generating plants that add power to our grid. (Gas plants are still the “marginal” power source, even though our grid is getting greener.)

Efficiency ratings on heat pumps are like the mileage ratings on automobiles: They represent the results of a particular test which often fails to reflect real world conditions. Research suggests that real world heat pump performance almost always falls somewhat short of rated performance. Research also suggests that results vary widely. Even for the same model pump, results can vary substantially across installations.

I do not fault the particular pump that we bought or our installers who were careful and professional. It may be, however, that we need better rules of thumb to predict how a pump will perform in a particular installation.

Our other disappointment was fully unexpected. Mid-winter, we noticed that our downstairs pump was peaking at a lower power level in each heating cycle. Although peaking lower in each cycle, it ran more of the time and seemed to be keeping up with heating needs, so we weren’t certain how to interpret the changes. But after a few weeks, we noticed that it was no longer keeping up and the downstairs apartment was getting cooler.

A service call revealed that the pump had leaked over half of its refrigerant. This is not an uncommon problem and our installer knew how to fix it, but it took a full of day of work. The original charge of the pump was 7.4 pounds of refrigerant, of which 4.1 pounds had leaked.

The most common refrigerant in heat pumps is a compound called R410A. It is a mix of greenhouse gases which together are over 2000 times more powerful than carbon dioxide. So, the 4 pounds of R410A equated to roughly 4 tons of carbon dioxide.

I have been reviewing the literature on heat pump efficiency and heat pump leaks and exploring with experts the policy implications, if any, of our experiences. For now, I just wanted to document and share our experiences.


Return to heat pump outline

Published by Will Brownsberger

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

72 replies on “Mixed heat pump results”

  1. Curious about installer competence. Heat pumps are sealed units with soldered joints = proper job will never leak unless a fatigue failure occurs do to improper loop isolation.
    Then max heat pump efficiency requires larger counter current heat exchangers so the maximum cooling/heating is reached and the working fluids are at equilibrium when they exit their heat exchanger. This can be done on budget or design reasons. Cheaper jobs are less efficient.

    1. I think our installer was good. I’d use them again. But I think the vibration levels in the standard mounting may be high. The pumps just sit on metal stilts that allow a lot of movement. We’ll see if the problem recurs.

  2. FYI: the general consensus at this site (https://news.ycombinator.com/item?id=35511332) is that you were sold a type of heat pump that was/is grossly inappropriate for the environment/location (i.e., with lengthy periods of below-freezing weather) at which it was installed. If so, that is very likely the cause of the observed (? egregious) lack of system efficiency.

    1. I think the heat pumps are fine in the cold — that aspect of their rating seems robust. I think the issue may be the extent of the duct work in our house — the fan may not be sized to pump enough air through the coil to take all available heat as the pump circulates refrigerant. The static pressure in our system may be higher than in the HSPF testing runs.

  3. Thanks for your honest report. It is refreshing to read a straight accounting.

  4. We had a heat pump downstairs and just installed one upstairs, and we’re very happy. The downstairs pump kept our entire house comfortable all winter and the only time we used the oil heat upstairs was during those few bitterly cold days.

  5. Is there info on efficiency of heat pumps for radiator systems? That is what we’d go for if my neighbors and I (our condo deed mandates shared heat) can ever get past the upfront cost of conversion. I know this type of pump exists, but is still in the minority. Thanks also for the info about the refrigerants, which is very dismaying and was news to me. Seems to take the advantage away from heat pumps if we have to keep producing GHG to run them (even when they don’t leak).

    1. There are heat pump hot water tanks. The heat pump, looking like an air conditioner, is at the top. However, one could see if a heat pump would heat water to 180 degrees for heating rather than 130-150 degrees for hot water. The lower temperature would require, at the least, larger radiators—a not starter I would think.

    2. I have heard that heat pumps don’t work well with hot water radiators, but geothermal might be the way to go. Geothermal uses similar technology but the compressor draws heat energy from underground instead of from the air. I think the tricky part is designing the underground installation.

  6. Will, We have the same problem with the cost of our Heat Pump (Ductless). Both appartments in our building are costing much more than the gas heat — just the opposite of what we expected.

  7. Thank you for the update on the performance of your heat pumps. I really appreciate how objectively you’re reporting on them.

  8. Thanks for the update. We are going to stay on gas, as (1) we have a functioning gas/forced hot water system and (2) we already spent a ton of cash on prior home maintenance. Why fix what ain’t broken?

  9. Thanks for experimenting and reporting back. It’s just one possible.solution, not the end all be all. Like public transit and electric vehicles, one solution in a particular context may give a bigger return.

  10. Thanks for updating your report. It seems as though we’re going through an early phase in transition to electric heating. One thing that is remarkable to me is that our heating systems seem to have have a much shorter lifespan than systems used up to the 1970’s. When replacing a functional system, there is a consideration of all the environmental costs of manufacturing and installation – and as a Yankee I would hang on to a system until it cannot be repaired any longer – unless there were a significant cost improvement.

    Also, as about 70% of the fossil fuel used to generate electricity is wasted in conversion and transmission, that seems wasteful on the face of it. If that electricity is going to be generated by burning fossil fuels, well, we’re inflating the amount of fuel we burn by 70% – unless we are using green electricity.

    I think I can get behind replacing my gas stove with electric to improve interior air quality, I already drive an electric car – and that is cheaper to operate (not to buy). For us, the installation would be complicated by the layout of the home and the ductwork, again reducing efficiency. Overall it seems like it would not be an improvement on environmental grounds and certainly not on cost. Our Mass Save consultation on this topic was not encouraging.

    For a more complicated floorplan, there is always the option to add a mini split on one area as a supplement. But it seems that is more appropriate to newer buildings with an open floorplan.

    Electrical generation and distribution info: https://insideenergy.org/2015/11/06/lost-in-transmission-how-much-electricity-disappears-between-a-power-plant-and-your-plug/

  11. I think we need to look at the bigger picture here. Methane leaking into our atmosphere causes severe environmental harm. Methane can escape from fracking (which is terrible for communities for several different reasons), super-emitter sites in methane production, or from leaks in pipelines. Just consider how many times you have “smelled gas” (or smelled the odorant added to methane “natural” gas, methyl mercaptan) when out for a stroll in Belmont. Moving to electric will greatly decrease methane release here and around the world. Try Googling “methane leaks.”
    As one letter-writer mentioned, we’re in a transition period now, and there’ll be wrinkles to be ironed out, and technology will improve. But a clean-energy future is imperative for our country and our world.

  12. Oh well. The good news is that each and every one of us has the solution to global warming and that’s to cease wasteful consuming.

  13. This is important info. Thanks for keeping us educated from your personal experience.
    “As it turned out, our heat pumps were only about 150% efficient, although they were rated 278% efficient.”
    It would seem that these #s don’t tell the whole story. We need a better system of analysis if we are going to properly design systems that don’t disappoint. Also, while leaks can occur, if it’s common as you say then something really really should change.

      1. This is a significant issue in the Refrigeration (and heat pump) industry – constant changing of refrigerants and it is expensive right now many people are charging $200 a pound for R-22 because it has been phased out (same with R-12) . CO2 is a complicated refrigerant and requires more expensive hardware and equipment
        I am proud of you for coming forward with your less than expected results – it helps people understand that the “All Electric” idea is not the ultimate solution.
        Now as an HVACR engineer – My concern is your leak ? what leaked and why ? a properly installed system should never leak – especially during the first five years (with out physical injury) . Another point I wish to make is recovery of refrigerants – Many systems become abandoned or just leak because of a technicians error (example last year I found four systems with out caps tightened on their service ports which lead to the loss of well over 200 LBS of refrigerant , two systems one lost 110 lbs , the second system 125 lbs ) I have also seen the propress (non braised) connections leak as well which is why a fully braised system is more reliable , However many mini split systems use flair connections which also tend to leak if not properly installed – so we need better standards for technicians and maybe insurance to insure that systems are properly installed – currently anyone can purchase a mini split system and install it themselves with out leak checking the system and often results in loss of refrigerant (and damage to the atmosphere) along with the expense of having a technician coming out and fixing the problem and adding more refrigerant. Maybe we need to have technicians certified by schools in technical competence instead of just needing the federally mandated 608 certification

        1. Our newly constructed house (2022) is heated and cooled by minisplits. We had issues after several months where refrigerant leaked out of the system. It was refilled and leaked again. It turned out that there were two leaks in the copper piping. Once these were found and fixed, there were no further problems. I urge you to have your installer test the tubing – our leaks were pinprick size. We understand that there have been numerous quality control issues in the manufacturing process recently.
          Also, I wonder if you have cleaned the filters in your minisplits? Monthly cleaning is recommended (and takes about 5 minutes). It makes a HUGE difference in the efficiency of your unit. Please try these things and follow up with the public! Thank you.

      2. The current refrigerants will be banned because duPont’s patent runs out in a few years, the very same reason R12 and R22 were banned, easy to do when you own some Congress critters. Nothing to do with the ozone layer, especially since those molecules are heavier than air anyway.

        1. The elephant in the room…big business. “Move along folks, nothing to see here.”

  14. Given what we know about the supply chain and its variability, the quality of manufacturing, the scarcity of experienced labor, the rising demand, and the critical implications of faulty evaluation of heat pumps, do we need an FDA of Heat Pumps and a licensing of installers?

    The FDA has its faults, licensing is not perfect, and the ‘war’ effort sufficient heat-pumps installed will be a singular effort of government and the private sector. Where is our Legislature on this?

    Do we have such an effort, state or federal?

    If government is part of the tool of reducing climate change, is government taking sufficient action?

    Who is or will be in charge of that effort?

    What must be said to affirm the intention? (The Globe Editorial today, was it, suggests part of the answer.)

    It is easy to say this. It is hard to see progress. It is hard to form an adequate, well thought out, and forcefully led government program with a chance of success.

    1. 1) FDA is not the licensing authority – EPA is and the Commonwealth on systems over 10 tons
      2) You only need a 608 certificate to basic installations and even chuck with a truck can go buy a mini split and install them with out any sort of certification
      3) there is no accountability for installations – no requirement for pressure testing

  15. I So appreciate this personal account. It’s not a story about “this happened to me”; it’s very clear.
    Perhaps you will remember me as the commenter who complained loudly about the survey choices
    “I’m OK with fossil fuels” which I found condescending and privledged. To answer a survey with my only choice being that I didn’t care about the environment enraged me.
    I run a biodiversity website.
    Thanks again

  16. That was my friend’s experience in his Brookline home as well. He ended up removing the whole setting and going back to gas,
    Once he bought a property in NH, he did a proper installation with deep well drilling and other considerations. Then he had a much better experience.

  17. You’ll see in future years how durable your system is. We put in heat pumps as part of the big push Boston did at the end of the Menino years; subsequent service calls have been accompanied by grumbles about the work — and about who got to do it. I’d take the grumbles as sour grapes if I hadn’t had a control-board failure, a leak in one set of lines (we needed two pumps to cover our house) and so many pinpoint leaks (according to a dye test) in a mini-split that the unit had to be replaced — contrary to a comment above, leaks can happen anywhere.

  18. There are certainly pros and cons to heat pumps and certain houses/configurations are certainly better suited for heat pumps. I’m curious about your electricity provider. Your can source your electricity through 100% renewable sources and Watertown had a really wonderful group buy a few years ago. You should certainly consider changing your electricity provider to one that is 100% renewable! Watertown is a leader in making this an affordable option and the state has a website that gives other options that are very competitively priced. At the very least, everyone can take this step to reduce their carbon footprint, and in some cases this is actually the cheapest option for electric delivery!

  19. I love that you shared this info. I hope that over time and with honest evaluations like this we can improve the products, process and outcomes. Thanks again!

  20. You said: “Research also suggests that results vary widely. Even for the same model pump, results can vary substantially across installations.” What are the factors that drive varying results? Why did your system have such variability?

    1. A lot of people are talking about this. My own working hypothesis is that the main issue is air flow. Heat pumps transfer a small amount of heat in each of many air flow cycles (by contrast to hotter sources like furnaces that blast a lot of heat in a few cycles). If air flow is constrained then the circulating refrigerant does not release all its heat indoors before it goes back out and the pump loops inefficiently. Air flow could be constrained by duct work pressure or by the placement of an air handler in a part of a room that accumulates hot air.

  21. If your are replacing an entire system and you have ductwork and a yard a GROUND SOURCE HEAT PUMP is my recommendation. They can drill the wells in a day and the air handler/compressor links directly into the existing ducts. We’ve had a system since 2012 and it’s been very efficient. Much more efficient to to use groundwater temp which is consistent than air temp which isn’t. Upfront costs are like replacing a furnace (after the tax benefits).

  22. Thanks, Will, this whole heat pump story is really interesting, and a very important topic. Electrification is a popular strategy for decarbonization, but this strategy relies on adding huge amounts of low-greenhouse power sources to the electricity grid. In Massachusetts, that means it relies on the offshore windmills specified in legislation actually being built and connected to our grid, and on the power line in Maine connecting New England’s grid to additional Canadian hydropower being completed. Until those two things happen most of our electricity will come from burning natural gas, and we won’t get the big environmental benefits from electrification that we need. We have quite a lot of building and buying to do: build all these windmills and power lines and some new substations to generate and handle the extra electricity, insulate our homes better and build EV chargers, and buy EVs and install heat pumps.

  23. Thank you for sharing, Will.
    We had a different experience as we were unable to use our heat pump for several years after we had it installed. Within a year and a half, the refrigerant began leaking out. The installer had difficulty isolating the source of the leak even after numerous service calls. After reading about “phantom” leaks in an online HVA chat forum, we realized that many others were having the same problem. The cause turned out to be the defective tubing (linesets) that was used in the installation which caused the refrigerant to leak out, ultimately rendering the system inoperable. Our installer (Prendergast Oil) refused to replace the defective line sets and refused to take any responsibility to rectify the problem. Eventually, after much time, energy and money, we found a different company to replace the defective linesets, a costly endeavor.
    A word to the wise – if installing a heat pump, insist on a warranty of at least 6 years or more on the linesets in addition to the regular warranty.

  24. This was our experience as well with our 4 ductless mini-split heat pumps re leaking refrigerant, therefore the back part of the house, getting the western sun, was never cooled enough in summer. We opted out of using it for heat because it wasn’t efficiently warming the home plus our usual gas HVAC systems pipes froze from non-use. In a new home, we opted for a very efficient gas system with combined on-demand hot water. For A/C, we opted for high velocity central air – a central product for old homes. Works beautifully.

  25. Hi Will,

    Thanks for posting about this! I’m guessing you’ve done this already, but did you fully insulate the attic? When we got ours installed we’d only insulated the floor (since, before then, we had been told a cold roof was good, I think maybe for preventing ice dams?) and we were disappointed with how much it was running in winter (particularly on backup resistance heat) and how expensive it was. We then learned that we needed to insulate the roof as well, since the unconditioned space makes the unit work a lot harder. (The installer never told us this, which, in hindsight, I find pretty surprising.) But ever since we insulated the space (we removed the batting in the floor and spray-foamed everything) it seems to be working a LOT better!

  26. Thank you for bringing us all this information, Will. Altering our heating systems to reduce greenhouse gasses is a goal for many of us, but the upfront costs and uncertainty about contractors in this new field makes us wary of taking the plunge. Honestly sharing your experience with heat pumps has been very helpful. I’ll read any of your updates with interest, for helpful tips if we ever decide to switch, or for suggestions of other methods as you continue to explore other possibilities.

  27. Will thanks so much – for your openness in sharing both facts and analysis.
    Just to make sure I understand your (lack of benefit) comparison: you are comparing your overall grid gas generated electric consumption with heat pump – vs. your prior gaz generated consumption?
    If prior your heat-pump, you had electric heating – that would have been still a benefits, consumption and GHG wise- correct?
    I am looking at the heat-pump more on the summer AC angle and solar PV coupling…

  28. I am grateful we can get an honest report and learn from someone else’s experience. This technology even though it has been around for 30 years, is still in it’s infancy and will take a lot of time to improve. 10 years ago I had the option of installing a heat pump water heater or installing solar domestic hot water heater. I also have a friend who went the heat pump path.
    My system uses natgas demand post heater and a PV powered circulator and a stainless steel tank. I calculated an annual usage of 59 therms extracted from collected data attributed to hot water . His system was at about 120Kwh/ month. He had to replace the unit after it leaked refrigerant into the water tank after the warranty expired. So far my system has been totally trouble free. Knock on wood, But I still get hot water in a power outage if the sun shines. Time will tell, but I made my energy choices

  29. Will, thanks for your good article and sharing your experience.

    I think the culprit here may be oversizing of the equipment (leak notwithstanding). In the spreadsheet you listed that the Manual J calculations came out to about 10,000 BTUH for the downstails system and about 13,500 BTUH for the upstairs system. (Note that Manual J calculations often overestimate heating and cooling loads. See this article about that from Energy Vanguard: https://www.energyvanguard.com/blog/got-manual-j-don-t-assume-it-s-correct/ ) Assuming that the Manual J calculations were correct though, the HVAC contractor installed two 1.5 ton heat pump systems that have a listed heating capacity of 20,000 BTUH. This is twice as large as the lower apartment needed and 50% larger than the upper apartment needed. And that is at the worst case scenario time of the heating season, only a few days a year. When heat pumps are oversized they never run at peak efficiency because they ramp up, meet the load quickly, shut back down, and never run in the high efficiency range that a longer run-time allows for. Even good high-quality systems like you have there, which are variable flow and can ramp down to try and meet the load at a given time, can only turn down so far and are often running at a higher capacity then needed on less than peak days. Your comment that you were always extremely comfortable even on the coldest day is another clue that this is the case.

    In a properly sized heat pump system (properly sized for maximizing efficiency) on the coldest days of winter the system will be running full-on and just *barely* not make your setpoint – so the house set to 70 degrees might only make it up to 68 or 69 degrees. That’s how you know it is perfect. Unfortunately that is NOT what most contractors want because that means that a typical untrained homeowner will think something is wrong and call for service. Thus most contractors figure out the manual J (hopefully correctly) and then round up to the next size of system so they won’t get that call back on a cold snap. But you as the homeowner end up with a less efficient system as a result. Your house would have been much better served with two one-ton heat pumps that have a heating capacity of about 12,000 – 13,000 BTUH each.

    Note that this oversizing also has consequences in the summer months while cooling. Air conditioning has a secondary benefit of dehumidifying the air as it cools it. However, when a cooling system is oversized then it also short-cycles, running for short bursts and turning off as the cooling temperature setpoint is met quickly. When this happens the system does not need to run long enough for enough air to move through the coil over time to do any significant dehumidifying before it turns off.. This can result in a cool, clammy house where people feel sticky despite the temperature being good and then often they turn the thermostat down using even more energy to try and get to a comfortable condition. It will be interesting to hear how your systems perform this summer.

    I am a big fan of heat pumps for residential heating and cooling and they are a critical step to meeting our energy and climate goals as a nation. When properly designed and installed, they also tend to make much more comfortable indoor environments for the occupants. I think that this educational piece of proper sizing, for both homeowners and contractors, is crucial for converting to heat pumps successfully and meeting our climate targets. Bigger isn’t always better. Hopefully this will change as heat pumps are more adopted and trusted and the technology is normalized for people.

    1. Thanks for this. We had a lot of conversation about sizing. I think you are right. It’s clear that the pumps have not been challenged by the load.

      But we talked to a lot of contractors and had a consultant assisting and no one wanted to go below the size we bought. Several wanted to go higher.

      We chose these pumps in recognition of our low load because their good rated turn-down potential, ability to run efficiently at below their capacity. But I don’t usually see them doing that — they are usually running at near their full power if they are running.

    2. I’m curious how you find a contractor who can properly size your system. So far, I’ve gotten three quotes. Two are proposing Mitsubishi systems which seem to be oversized for my 1200 square foot house. Another contractor is recommending a smaller sized Fujitsu system that he says will be more appropriate for my size/style of house. It’s hard to know who to trust when considering an investment that is this costly. I really just wanted mini splits for ac, but I started considering them as a heat source because of the rebates and incentives. I currently have oil heat. I’m still not sure I’m ready to make the switch.

  30. Thanks for the info, Will. Could you share how you determined your system was leaking, and lacking efficiency?
    I’m happy with my ductless mini-split so far (1.5 yrs). It gave us AC, and offset ~50% of our natural gas heat this winter. Ten solar panels added to the roof more than cover all the electricity use (and Biden gave us %30 of their installation cost back when I filed my taxes). Incentives work!

    1. The amount of the leakage was based on the report of the AC repair person: The initial weight of refrigerant had been documented on installation. Before repairing the leak and recharging the system, they evacuated the system and weighed-out the refrigerant that was remaining in it.

      All efficiency computations are contained in the spreadsheet linked to within the post and also in the “Resources” section at the bottom of the post.

  31. Thank you for a candid and thoughtful analysis. Sometimes ideology gets in the way of the ultimate goal of a cleaner, greener environment. (And other things as well–I’m a pragmatist, not an ideologue.) Transparent data is the best way for us to consider and adopt the best portfolio of policies to address global warming in a holistic and effective fashion.

  32. Thanks Will, and others. A lot of good information. Where are best places to get an analysis and advice? We have one large mini split downstairs, great for cooling and good for supplemental heating; two smaller minis upstairs for cooling and (uneven) heating (5 rooms plus bath). Considering one or two more, downstairs or upstairs. Would like to use our oil as a backup – we still rely on it in the winter. And we recently installed solar panels which greatly reduced our electric bill.

  33. That’s unfortunate, especially since you supported a $10,000 tax credit for everybody who removes their natural gas system, and installs an electric heat pump, in Massachusetts I’m assuming you got that tax credit yourself, for removing the natural gas heating system from your home?

    I mentioned before on one of your other blogs that I thought you were putting the cart before the horse on this issue, particularly since Massachusetts currently gets the majority of its electricity from natural gas.

    In any case, thank you for the candid analysis on your own experience. Perhaps you will do some more research about the “warp speed operation” COVID vaccines you supported mandates for too? Dr. Meryl Nass (MD) has just written an up-to-date summary of the current research on that matter based on the latest information provided by the CDC. Here’s the link for your review: https://merylnass.substack.com/p/its-official-cdc-and-uk-government

    1. Hi PJ, yes, I used the Mass Save Rebates and also Belmont Light Department rebates. Those are detailed in the attached spreadsheet. Those are utility-designed rebates, as opposed to tax credits. They are not subject to legislative approval.

  34. Appreciate your candid feedback! People need to fully understand the pros and cons of this new(ish) heating method in order to make the best decision for their household. It’s important to understand that no heating method is perfect but some are better than others depending on your unique household. In my household, natural gas via a high efficiency boiler (Weissman) has proved best. I also have a mini split but rarely use for heat. I use for AC mainly and it does an OK job (but also drives up the electric bill).

  35. Great information and thanks for sharing Will. On the point about refrigerants there is a push in the HVAC industry to get lower GWP and 0 ODP A2L class refrigerants adopted into the building codes for in-building use and not waiting for the next IBC code cycles to come around to adopt the latest ASHRAE 35 &15 standards. We could use your help advocating for this in Massachusetts:


    “These approvals, which go into effect with the 2024 IBC, IFC and IMC, permit the use of A2L refrigerants for human comfort uses, consistent with industry standards, and will help to facilitate the phasedown of HFCs following EPA rules.”

  36. As a engineer and staunch republican who still remains skeptical of global warming. I want to first state that I found your previous post regarding cop issues outstanding. Engineers, for the most part, can’t function without real world proof of concepts from which to build upon. I had searched the internet to exhaustion for actual cop data, only finding fiction and sales pitches instead, of which there are thousands. Your data is invaluable to me.
    Let me just a make couple of comments by doing the math rather than the science. First, whoever told you you were going to save money compared to a new natural gas system just plain lied to you. This is simply because of the very low price per btu for this fuel source. If you had replaced a propane or oil fired furnace you would likely be at least somewhat happier. Natural gas is still about half the price (or even less) of oil or propane.
    Second, most state of the art heat pumps use variable speed compressors. This simply means instead of a powerful compressor and fan coming on and going off repeatedly in your back yard, a variable speed compressor and fan simply slow down or speed up but never go off. I believe this is an essential part of an efficient cold winter heat pump. There are lots of reasons for this.
    Third, and I’ll close on this, the power electronics on heat pumps is woefully inadequate. Clearly what is needed goes well beyond a cool wifi remote. A good system should tell you it’s leaking refrigerant! It should tell you how it’s doing overall and in detail. Progress is being made on this front but until more people like you speak up, manufacturers are not going to add cost to their product unless it is perceived as having value in the marketplace.
    As a republican, in Maine, I see a very different, and to me more important problem to solve. There are entirely too many Mainers who are now “too poor” to be able to adequately heat their homes. I still think improvements can be made to heat pumps to greatly increase cop from what it actually is today. Very few Mainers have natural gas hookups, unfortunately. Fuel oil and propane have to go! That puts both on the same team.

  37. The fact that “this was not a great move” for you is interesting…As you may be aware the MA DEP is promulgating a Clean Heat Standard, with the intention of eliminating delivered fuels (heating oil and propane) and forcing MA homeowners to move to heat pumps. Since your experiment was most likely costly up front, not economical in its operation, and did not provide a level of comfort that you had with your conventional system, can you get on board with the DEP’s legislation by regulation, which will only hurt consumers? Can you get behind this given your experience?

    I find it interesting that ISO New England lists NatGas as 52% of it’s resource mix for power generation. It lists just 7% for wind and solar. As such, is “electrifying everything” really helping anything? I also find it interesting that the heating oil trade has shown a path to Net Zero through Biofuels, but the DEP and other decision makers refuse to even give this consideration – despite the fact that other progressive states such as CA and OR have. Is all or nothing, given the disappointing state of heat pump performance and the current resource mix, really a good policy path?

    Additionally, are we really ready, from a electrical grid standpoint, for electrification? I have two letters in my possession, one from the President of Eversource and the other from Groton Electric, that warned of blackouts over the winter if we had prolonged cold. This didn’t come to pass, but are we heading for disaster when we move domestic space heating and transportation fuels to a grid that can barely get by on current demand? To me, it’s like continuing to plug things into the same outlet, overloading it, and wishing and hoping the breaker won’t trip…given these utilities warnings (ISO New England made similar ones) are we putting the cart before the horse here?

  38. My Daikin heat pump [18,000 btu] was great for six years, sized just a little over for the new energy retrofit my house got, and then started developing a maddeningly small leak that *nobody* could find. After the third $800 truck roll to pull what was left and recharge I said I was done with that, got myself 608 certified so I could buy refrigerants and top it up myself, and kept hunting — throwing sniffers, bubbles, Nylog, UV dye, etc at the problem and still couldn’t find it. I didn’t have to pull and weigh in an entire charge since at that point when it started struggling in the winter, I knew exactly how much more to add to set things right again. Unfortunately I’m nowhere near ready to replace the system yet, so this is the way I can limp it along until that time comes or I actually find the leak and hopefully it’s an inexpensive repair.

    Minor point — as refrigerant leaks out of a system, the pressure does *not* change as long as there’s a saturate mix inside, part gas and part liquid. Only when all the liquid is gone, does pressure drop as the rest of the gas leaks away. That’s part of the real magic of refrigerants.

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