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Do you have a heat pump for heating? If you do, you get A/C for 'free', and if you don't, you're wasting so much energy in the winter that you can never make u

Do you have a heat pump for heating? If you do, you get A/C for 'free', and if you don't, you're wasting so much energy in the winter that you can never make up for it by 'making do' with a fan rather than proper air conditioning. Signed, some guy who was in Belgium for the heat wave in 2018 and thinks Europeans should just suck it up and put in heat pumps. Sweltering in the summer and burning gas directly in the winter isn't virtuous.

eru 4y ago
> If you do, you get A/C for 'free', and if you don't, you're wasting so much energy in the winter that you can never make up for it by 'making do' with a fan rather than proper air conditioning. Eh, depends on what you are heating with in winter. A friend of mine lives in a rural area and basically gets firewood for free. Even the best heat pump can't beat that. (Heat pumps are still great in general. And much better than using electricity directly to heat.)
- samatman 4y ago
  If your labor has no value, sure. There's something satisfying about trading labor directly for something like heat that you normally have to buy. Exercise is good for you, sustainability and resilience are virtues, and so on. But heating even a modest space with wood is a Lot of Work. Also, it's still quite energetically inefficient, but that's a technicality here I feel, energy isn't completely fungible (it does salvage my sentence, which was about energy). The carbon accounting would be interesting to spitball but fiendishly hard to do fairly.
sokoloff 4y ago
I have been researching heat pumps, in my case air-to-water, so I could get very cold water “cheaply” in the summer, but it’s still a massive project to turn that into AC. I probably can’t make it work, because I need a bit too high water circulation temps to meet the heating load at 12°F/-11°C and the up-front economics are significantly worse due to not enough experienced installers/general lack of competition in the air-to-water space. (Our gas prices are low enough and electricity high enough that the payback period is lengthy.) If I had existing ducts, air-to-air heat pumps would make a lot of sense (and would give AC automatically), but hydronic distribution doesn’t afford “free” AC.
- dahfizz 4y ago
  How does an air to water heat pump work? Do you live in a climate that gets below freezing in the winter?
  - sokoloff 4y ago
    I live in the Boston area (temps well below freezing in winter). Freezing is managed by either a monobloc design using glycol in the outdoor loop (more common) or by sending only refrigerant in/out of the building (less common) and having the heat transfer take place inside. If you use glycol, you’d typically use a plate heat exchanger inside and still use water as the main hydronic distribution medium (out to radiators in my case or to floor warming in other installs), but this gives up a small amount of efficiency and some maximum heating capacity. (If the max leaving glycol temp is 130°F/55°C, your max water temp will be a few degrees below that after the heat exchanger.) The split units (refrigerant lines in/out of the building) can go directly to water, meaning a max leaving temp of 130°F can go directly to the radiator loops.
    - samatman 4y ago
      I don't know if you watch Technology Connections already, but his videos on this are really good. He lives in the Chicago area. I get the sense that you've evaluated this thoroughly and it actually won't work for you, that does happen. We get bitter cold as well as sultry summers, and I have an AC which I keep thinking about replacing with a heat pump, just because it bothers me aesthetically that I can't run it backward for the intermediate months when it's cold but not that cold. The bill would be cheaper but the depreciation on replacing a perfectly good AC would take a long time to balance.
      - sokoloff 4y ago
        I haven’t, but will check his channel out. In return, I’ll recommend Heat Geek (based in UK). (Edit to correct: I actually had seen at least one his videos from my YouTube history. That reinforces my recommendation for “if you like him, you’ll likely enjoy Heat Geek as well”.) In terms of “can it work for me?” it’s like most things: if you hit it hard enough, it’ll fit, but the low cost of replacing a boiler with a boiler, the high cost of electricity in MA, and the dearth of A2W heat pump companies (both competing to supply equipment in the US and locally installing) makes it uneconomical, not thermodynamically impossible. (It’s right on the edge but inside of the latter; via experimentation this winter, I determined that my 2 lower levels can maintain temp down to 10°F with a leaving water temp cycling between 125-135°F, while the converted attic needs 135-145°F at 10°F OAT. Most A2W heat pumps max out at 55°C/130°F leaving water temp, and even at that level are necessarily giving up efficiency and heating capacity as compared to a 45°C or 50°C LWT.) Obviously, improving insulation would change those figures, but in a structural brick house with complex interior wall finishes, adding radiation in the attic and supplementing the heat pump with an electric boiler below 15°F OAT would be wildly cheaper, especially since the COP at those temps is well under 2 and the runtimes under 15°F would only be around 50-75 hours per year. It could work, and would allow us to get rid of local fuel combustion entirely, but even after a $10K government incentive, it would be at a cost that is still a multiple of what gas-for-gas replacement ($2.5K government incentive) and running for 15 years would cost and with the risk of having an uncommon system that only a few companies understand and can service. Perhaps the boiler after this next one will be replaced by a heat pump; I hope things develop in that direction. We may end up adding some mini-split (air-air) heat pumps, mostly to provide AC and dehumidification in the summer (replacing window shaker units), but those would also be quite economical to heat with in the long shoulder season (40-60°F OATs).
moffkalast 4y ago
Everyone who has heat pumps knows they can cool, the issue is getting one because they kinda cost like 5x as much as an equivalent AC unit for some goddamn reason and the only difference is the reversing valve. I suspect the market needs some EU regulation so the manufacturers stop price gouging based on marketing bullshit.
- farisjarrah 4y ago
  On amazon in the US you can get either a 12,000 btu through-the-wall AC unit for about $700 or a 12,000 btu wall ductless mini-split(heat pump, so AC and heat) for about $850. For either of those you can find models for cheaper or more expensive. I just chose general middle of the road prices. So the cost is no longer 5x, the prices are becoming a lot more comparable for heat pumps vs regular ac units. Also, if you check out the efficiency ratings, for most mini-splits these days, you'll make up the cost difference in your electrical bill vs a run of the mill AC unit in the medium to long run.
  - eropple 4y ago
    Your mention of through-wall models reminded me: I've been wondering for a while why I can't get window-mounted heat pumps at a reasonable price. I recognize the limitations on insulation, but as I'm not yet at a spot in my renovation where I can do heat pumps comprehensively and seeing as how I'm looking for another air conditioner for the first floor of my house, buying one that's reversible seems like an obvious thing. (Maybe like that around-the-window Midea model? That seems kind of obvious to me, but I am not an engineer.) This startup has a neat idea, and I hope to see more about it - https://www.gradientcomfort.com/ https://www.gradientcomfort.com/ - but $2000 feels like it's not competitive. And if anyone happens to know of one (and not an AC that will just do electric heat) available in the USA, I'd be grateful to hear about it. Amana will sell me one - for $1300 for 12K BTU, and that sounds...high.
    - moffkalast 4y ago
      If only it were possible to use something like that with tilt turn style windows.

eru 4y ago

> If you do, you get A/C for 'free', and if you don't, you're wasting so much energy in the winter that you can never make up for it by 'making do' with a fan rather than proper air conditioning. Eh, depends on what you are heating with in winter. A friend of mine lives in a rural area and basically gets firewood for free. Even the best heat pump can't beat that. (Heat pumps are still great in general. And much better than using electricity directly to heat.)

samatman 4y ago
If your labor has no value, sure. There's something satisfying about trading labor directly for something like heat that you normally have to buy. Exercise is good for you, sustainability and resilience are virtues, and so on. But heating even a modest space with wood is a Lot of Work. Also, it's still quite energetically inefficient, but that's a technicality here I feel, energy isn't completely fungible (it does salvage my sentence, which was about energy). The carbon accounting would be interesting to spitball but fiendishly hard to do fairly.

sokoloff 4y ago

I have been researching heat pumps, in my case air-to-water, so I could get very cold water “cheaply” in the summer, but it’s still a massive project to turn that into AC. I probably can’t make it work, because I need a bit too high water circulation temps to meet the heating load at 12°F/-11°C and the up-front economics are significantly worse due to not enough experienced installers/general lack of competition in the air-to-water space. (Our gas prices are low enough and electricity high enough that the payback period is lengthy.) If I had existing ducts, air-to-air heat pumps would make a lot of sense (and would give AC automatically), but hydronic distribution doesn’t afford “free” AC.

dahfizz 4y ago
How does an air to water heat pump work? Do you live in a climate that gets below freezing in the winter?
- sokoloff 4y ago
  I live in the Boston area (temps well below freezing in winter). Freezing is managed by either a monobloc design using glycol in the outdoor loop (more common) or by sending only refrigerant in/out of the building (less common) and having the heat transfer take place inside. If you use glycol, you’d typically use a plate heat exchanger inside and still use water as the main hydronic distribution medium (out to radiators in my case or to floor warming in other installs), but this gives up a small amount of efficiency and some maximum heating capacity. (If the max leaving glycol temp is 130°F/55°C, your max water temp will be a few degrees below that after the heat exchanger.) The split units (refrigerant lines in/out of the building) can go directly to water, meaning a max leaving temp of 130°F can go directly to the radiator loops.
  - samatman 4y ago
    I don't know if you watch Technology Connections already, but his videos on this are really good. He lives in the Chicago area. I get the sense that you've evaluated this thoroughly and it actually won't work for you, that does happen. We get bitter cold as well as sultry summers, and I have an AC which I keep thinking about replacing with a heat pump, just because it bothers me aesthetically that I can't run it backward for the intermediate months when it's cold but not that cold. The bill would be cheaper but the depreciation on replacing a perfectly good AC would take a long time to balance.
    - sokoloff 4y ago
      I haven’t, but will check his channel out. In return, I’ll recommend Heat Geek (based in UK). (Edit to correct: I actually had seen at least one his videos from my YouTube history. That reinforces my recommendation for “if you like him, you’ll likely enjoy Heat Geek as well”.) In terms of “can it work for me?” it’s like most things: if you hit it hard enough, it’ll fit, but the low cost of replacing a boiler with a boiler, the high cost of electricity in MA, and the dearth of A2W heat pump companies (both competing to supply equipment in the US and locally installing) makes it uneconomical, not thermodynamically impossible. (It’s right on the edge but inside of the latter; via experimentation this winter, I determined that my 2 lower levels can maintain temp down to 10°F with a leaving water temp cycling between 125-135°F, while the converted attic needs 135-145°F at 10°F OAT. Most A2W heat pumps max out at 55°C/130°F leaving water temp, and even at that level are necessarily giving up efficiency and heating capacity as compared to a 45°C or 50°C LWT.) Obviously, improving insulation would change those figures, but in a structural brick house with complex interior wall finishes, adding radiation in the attic and supplementing the heat pump with an electric boiler below 15°F OAT would be wildly cheaper, especially since the COP at those temps is well under 2 and the runtimes under 15°F would only be around 50-75 hours per year. It could work, and would allow us to get rid of local fuel combustion entirely, but even after a $10K government incentive, it would be at a cost that is still a multiple of what gas-for-gas replacement ($2.5K government incentive) and running for 15 years would cost and with the risk of having an uncommon system that only a few companies understand and can service. Perhaps the boiler after this next one will be replaced by a heat pump; I hope things develop in that direction. We may end up adding some mini-split (air-air) heat pumps, mostly to provide AC and dehumidification in the summer (replacing window shaker units), but those would also be quite economical to heat with in the long shoulder season (40-60°F OATs).

moffkalast 4y ago

Everyone who has heat pumps knows they can cool, the issue is getting one because they kinda cost like 5x as much as an equivalent AC unit for some goddamn reason and the only difference is the reversing valve. I suspect the market needs some EU regulation so the manufacturers stop price gouging based on marketing bullshit.

farisjarrah 4y ago
On amazon in the US you can get either a 12,000 btu through-the-wall AC unit for about $700 or a 12,000 btu wall ductless mini-split(heat pump, so AC and heat) for about $850. For either of those you can find models for cheaper or more expensive. I just chose general middle of the road prices. So the cost is no longer 5x, the prices are becoming a lot more comparable for heat pumps vs regular ac units. Also, if you check out the efficiency ratings, for most mini-splits these days, you'll make up the cost difference in your electrical bill vs a run of the mill AC unit in the medium to long run.
- eropple 4y ago
  Your mention of through-wall models reminded me: I've been wondering for a while why I can't get window-mounted heat pumps at a reasonable price. I recognize the limitations on insulation, but as I'm not yet at a spot in my renovation where I can do heat pumps comprehensively and seeing as how I'm looking for another air conditioner for the first floor of my house, buying one that's reversible seems like an obvious thing. (Maybe like that around-the-window Midea model? That seems kind of obvious to me, but I am not an engineer.) This startup has a neat idea, and I hope to see more about it - https://www.gradientcomfort.com/ https://www.gradientcomfort.com/ - but $2000 feels like it's not competitive. And if anyone happens to know of one (and not an AC that will just do electric heat) available in the USA, I'd be grateful to hear about it. Amana will sell me one - for $1300 for 12K BTU, and that sounds...high.
  - moffkalast 4y ago
    If only it were possible to use something like that with tilt turn style windows.