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The notion that heat pumps don’t work at low temperatures hasn’t been true for years. I think you may be surprised to find that just about any heat pump you loo

The notion that heat pumps don’t work at low temperatures hasn’t been true for years. I think you may be surprised to find that just about any heat pump you look at has good efficiency down to very low temperatures.

Loughla 1y ago
Define low temperatures. Mine struggles if it gets below 30, and might as well not exist below 10. They're not great at low temps.
- doctorhandshake 1y ago
  I’m not sure what yours is but it doesn’t sound appropriate to your application. Mitsubishi hyper heat is indicative of a contemporary inverter design - 100% efficiency to -5f: https://www.mitsubishicomfort.com/articles/mythbusters-heat-pumps-for-extreme-cold-climates https://www.mitsubishicomfort.com/articles/mythbusters-heat-...
  - sokoloff 1y ago
    100% efficiency is terrible for a heat pump. Electric resistance heat is 100% efficient.
    - doctorhandshake 1y ago
      I should have said 100% performance. COP is typically 3-4:1 with mitsu
      - sokoloff 1y ago
        Typical seasonal average? Sure. At -5°F? Hell no! At +5°F, they rate their own equipment to have a 2.0 CoP. https://mylinkdrive.com/viewPdf?srcUrl=http://s3.amazonaws.com/enter.mehvac.com/DAMRoot/Original/10007%5CM_SUBMITTAL_MXZ-4C36NAHZ2-en.pdf https://mylinkdrive.com/viewPdf?srcUrl=http://s3.amazonaws.c...
        throw0101a 1y ago
        Here's a Trane/Mitsubishi unit that has a COP of (at least) 3 at -13F/-25C: * https://ashp.neep.org/#!/product/156605/7/25000/95/7500/0///0 https://ashp.neep.org/#!/product/156605/7/25000/95/7500/0///... An LG unit with 2.4 at -4F/-20C: * https://ashp.neep.org/#!/product/29688/7/25000/95/7500/0///0 https://ashp.neep.org/#!/product/29688/7/25000/95/7500/0///0 Searchable database of cold climate air source heat pumps (ccASHPs): * https://ashp.neep.org/#!/product_list/ https://ashp.neep.org/#!/product_list/
        sokoloff 1y ago
        Correct (and thanks for the link to that unit). Though it’s worth noting that that first 2 ton rated unit is putting out 0.5 tons (6k BTU/hr) at that temp and rating. That’s not going to be particularly helpful for a structure that needed 24k BTU/hr during warmer temps, meaning the owner of the unit is likely mixing in a lot of 1.0 BTUs to meet the heat loss at -13°F.
        throw0101a 1y ago
        > Though it’s worth noting that that first 2 ton rated unit is putting out 0.5 tons (6k BTU/hr) at that temp and rating. I just did a quick search for "all" units and sorted the result list/table by COP@5F. If one was actually shopping/designing a solution then a more nuanced search criteria would be used. Further, you'd probably want to do a (US ACCA) Manual J calculation to first determine how much energy is needed (j = joules) * https://www.youtube.com/@HomePerformance/search?query=manual%20j https://www.youtube.com/@HomePerformance/search?query=manual... Then the (US ACCA) Manual S (select) to figure out your equipment: * https://www.youtube.com/@HomePerformance/search?query=manual%20s https://www.youtube.com/@HomePerformance/search?query=manual... One can lookup the 1% (or 0.4%) of coldest/hottest days for your area, which would help determine what one actually has to typically worry about: * https://ashrae-meteo.info/v2.0/ https://ashrae-meteo.info/v2.0/ * https://www.airequipmentcompany.com/2021/what-does-design-day-really-mean/ https://www.airequipmentcompany.com/2021/what-does-design-da...
- crazygringo 1y ago
  I've got one about 8 years old, and it does just fine down to 0°F (it hasn't gotten colder than that here). It doesn't even have any kind of auxiliary heat. It's fine. The only difference when it's super-cold is that the air coming out of it isn't as warm, so the heating cycle stays on for a longer proportion of the time. But it keeps it 70°F inside no problem at all.
- tzs 1y ago
  That's one of the older style units. Starting in 2007 when Mitsubishi introduced their "Hyper-Heating Inverter" heat pumps, and continuing with Fujitsu and Daikin following with similar technology in the 2010-12 timeframe, and others a few years later, heat pumps got way better in the cold. Mitsubishi's maintain 200%+ efficiency down to -4℉ (-20℃) and 150% down to -22℉ (-30℃) [1]. Only a few towns in the continental US get below that, and even those aren't going to get cold enough long enough to make it worth it an an all electric home to switch to your emergency electrical resistance heating. Their capacity doesn't start dropping until you get down to 23℉ (-5℃), dropping to 76% at -13℉ (-25℃). [1] https://www.coolingpost.com/world-news/study-proves-heat-pump-efficiency-at-low-temperatures/ https://www.coolingpost.com/world-news/study-proves-heat-pum...
- throw0101a 1y ago
  > Mine struggles if it gets below 30, and might as well not exist below 10. They're not great at low temps. What percentage of the (US) population gets temperatures like that? That's generally mostly IECC Zone 7 (though cold snaps in Zone 6) can happen: * https://basc.pnnl.gov/images/iecc-climate-zone-map https://basc.pnnl.gov/images/iecc-climate-zone-map ASHRAE—an HVAC organization—has data on the coldest and hottest days for areas so that you can design things for the coldest or hottest 1% of the year (4 hottest/coldest days): * https://ashrae-meteo.info/v2.0/ https://ashrae-meteo.info/v2.0/ I think that if you have an older, leaky/ier, less-insulated house you may need to 'brute force' heating your (probably older) domicile. But if you have a <4 ACH@50 air tightness, and reasonable insulation levels, a good portion of the US population could make do with a heat pump. Mitsubishi publishes data were they have 100% heating capacity at -15C, which some models being 100% at -20C and -23C: * https://www.mitsubishielectric.ca/en/hvac/home-owners/zuba https://www.mitsubishielectric.ca/en/hvac/home-owners/zuba At -25C they have 80% capacity: * https://www.mitsair.com/wp-content/uploads/2024/10/MEM-202406-E_ZubaRebrandBroch_LR_FIN-1.pdf https://www.mitsair.com/wp-content/uploads/2024/10/MEM-20240...
  - whateveracct 1y ago
    > What percentage of the (US) population gets temperatures like that? That's generally mostly IECC Zone 7 (though cold snaps in Zone 6) can happen: A lot? e.g. Chicago gets it every year
    - throw0101c 1y ago
      >>> Mine struggles if it gets below 30, and might as well not exist below 10. They're not great at low temps. >> > What percentage of the (US) population gets temperatures like that? That's generally mostly IECC Zone 7 (though cold snaps in Zone 6) can happen: > A lot? e.g. Chicago gets it every year [citation needed] Per historical weather data: https://ashrae-meteo.info/v2.0/index.php?lat=41.960&lng=-87.932&place=%27%27&wmo=725300 https://ashrae-meteo.info/v2.0/index.php?lat=41.960&lng=-87.... It is warmer than -16C/3F at Chicago (O'Hare) for 99% of the time (i.e., except for 4 days a year), and warmer than -18.7C/-2F for 99.6% of the time (2 days). ASHRAE are the folks that publish the heating/cooling standards that are used in building codes for estimate heating/cooling equipment capacities (Manual J) and selecting the right equipment (Manual S). Here's a PDF with a lot of locations in the US and CA (and other countries further down), and if you look under the "Heating DB" column, you'll find very few US locations that have -30F under the 99% (or even 99.6%) sub-columns: * https://www.captiveaire.com/catalogcontent/fans/sup_mpu/doc/winter_summer_design_temps_us.pdf https://www.captiveaire.com/catalogcontent/fans/sup_mpu/doc/... So unless you're in AK, MN, or ND, long runs of temperatures colder than -20F/-30C don't happen too often. Of course if you have a leaky house with little insulation, you're throwing money out the window/door, so the first consideration for a good ROI is better air sealing and insulation.
crgwbr 1y ago
That’s true, but still doesn’t always make heat pumps the most cost effective choice to operate. For example, last winter I paid an average of $0.24/kWh for electricity vs $0.05/kWh for natural gas. Even if a heat pump had a perfect 4.0 COP all winter, gas would be ~15% cheaper. Electricity prices really need to come down before it will be viable for everyone.
- doctorhandshake 1y ago
  Yeah. Sadly the trend does not seem to be heading that direction what with the current admin’s … policies and the whole … AI … thing.
- kragen 1y ago
  Get solar.
  - crgwbr 1y ago
    I’ve tried. For it to be at all viable on my property, I’d need to cut down a bunch of trees. I’d rather keep the trees and pay someone else with solar panels.
    - kragen 1y ago
      That makes sense. Is that legal?
      - kragen 1y ago
        I mean, in many countries, often either the government or a company closely allied to the government has been granted a legal monopoly on selling electrical energy, so buying electricity from other people is illegal.
- etimberg 1y ago
  Not to mention, lots of places have time of use electricity pricing which makes it even worse. This is the problem with running my heatpump when its cold, some of the coldest times (right before dawn) coincide with peak time-of-use prices
sokoloff 1y ago
They have good heat output down to very low temperatures, but not good efficiency. The CoP is often around 2.0 at those very low temps, though (and of course the heat energy demanded is higher).

Loughla 1y ago

Define low temperatures. Mine struggles if it gets below 30, and might as well not exist below 10. They're not great at low temps.

doctorhandshake 1y ago
I’m not sure what yours is but it doesn’t sound appropriate to your application. Mitsubishi hyper heat is indicative of a contemporary inverter design - 100% efficiency to -5f: https://www.mitsubishicomfort.com/articles/mythbusters-heat-pumps-for-extreme-cold-climates https://www.mitsubishicomfort.com/articles/mythbusters-heat-...
- sokoloff 1y ago
  100% efficiency is terrible for a heat pump. Electric resistance heat is 100% efficient.
  - doctorhandshake 1y ago
    I should have said 100% performance. COP is typically 3-4:1 with mitsu
    - sokoloff 1y ago
      Typical seasonal average? Sure. At -5°F? Hell no! At +5°F, they rate their own equipment to have a 2.0 CoP. https://mylinkdrive.com/viewPdf?srcUrl=http://s3.amazonaws.com/enter.mehvac.com/DAMRoot/Original/10007%5CM_SUBMITTAL_MXZ-4C36NAHZ2-en.pdf https://mylinkdrive.com/viewPdf?srcUrl=http://s3.amazonaws.c...
      - throw0101a 1y ago
        Here's a Trane/Mitsubishi unit that has a COP of (at least) 3 at -13F/-25C: * https://ashp.neep.org/#!/product/156605/7/25000/95/7500/0///0 https://ashp.neep.org/#!/product/156605/7/25000/95/7500/0///... An LG unit with 2.4 at -4F/-20C: * https://ashp.neep.org/#!/product/29688/7/25000/95/7500/0///0 https://ashp.neep.org/#!/product/29688/7/25000/95/7500/0///0 Searchable database of cold climate air source heat pumps (ccASHPs): * https://ashp.neep.org/#!/product_list/ https://ashp.neep.org/#!/product_list/
        sokoloff 1y ago
        Correct (and thanks for the link to that unit). Though it’s worth noting that that first 2 ton rated unit is putting out 0.5 tons (6k BTU/hr) at that temp and rating. That’s not going to be particularly helpful for a structure that needed 24k BTU/hr during warmer temps, meaning the owner of the unit is likely mixing in a lot of 1.0 BTUs to meet the heat loss at -13°F.
        throw0101a 1y ago
        > Though it’s worth noting that that first 2 ton rated unit is putting out 0.5 tons (6k BTU/hr) at that temp and rating. I just did a quick search for "all" units and sorted the result list/table by COP@5F. If one was actually shopping/designing a solution then a more nuanced search criteria would be used. Further, you'd probably want to do a (US ACCA) Manual J calculation to first determine how much energy is needed (j = joules) * https://www.youtube.com/@HomePerformance/search?query=manual%20j https://www.youtube.com/@HomePerformance/search?query=manual... Then the (US ACCA) Manual S (select) to figure out your equipment: * https://www.youtube.com/@HomePerformance/search?query=manual%20s https://www.youtube.com/@HomePerformance/search?query=manual... One can lookup the 1% (or 0.4%) of coldest/hottest days for your area, which would help determine what one actually has to typically worry about: * https://ashrae-meteo.info/v2.0/ https://ashrae-meteo.info/v2.0/ * https://www.airequipmentcompany.com/2021/what-does-design-day-really-mean/ https://www.airequipmentcompany.com/2021/what-does-design-da...
crazygringo 1y ago
I've got one about 8 years old, and it does just fine down to 0°F (it hasn't gotten colder than that here). It doesn't even have any kind of auxiliary heat. It's fine. The only difference when it's super-cold is that the air coming out of it isn't as warm, so the heating cycle stays on for a longer proportion of the time. But it keeps it 70°F inside no problem at all.
tzs 1y ago
That's one of the older style units. Starting in 2007 when Mitsubishi introduced their "Hyper-Heating Inverter" heat pumps, and continuing with Fujitsu and Daikin following with similar technology in the 2010-12 timeframe, and others a few years later, heat pumps got way better in the cold. Mitsubishi's maintain 200%+ efficiency down to -4℉ (-20℃) and 150% down to -22℉ (-30℃) [1]. Only a few towns in the continental US get below that, and even those aren't going to get cold enough long enough to make it worth it an an all electric home to switch to your emergency electrical resistance heating. Their capacity doesn't start dropping until you get down to 23℉ (-5℃), dropping to 76% at -13℉ (-25℃). [1] https://www.coolingpost.com/world-news/study-proves-heat-pump-efficiency-at-low-temperatures/ https://www.coolingpost.com/world-news/study-proves-heat-pum...
throw0101a 1y ago
> Mine struggles if it gets below 30, and might as well not exist below 10. They're not great at low temps. What percentage of the (US) population gets temperatures like that? That's generally mostly IECC Zone 7 (though cold snaps in Zone 6) can happen: * https://basc.pnnl.gov/images/iecc-climate-zone-map https://basc.pnnl.gov/images/iecc-climate-zone-map ASHRAE—an HVAC organization—has data on the coldest and hottest days for areas so that you can design things for the coldest or hottest 1% of the year (4 hottest/coldest days): * https://ashrae-meteo.info/v2.0/ https://ashrae-meteo.info/v2.0/ I think that if you have an older, leaky/ier, less-insulated house you may need to 'brute force' heating your (probably older) domicile. But if you have a <4 ACH@50 air tightness, and reasonable insulation levels, a good portion of the US population could make do with a heat pump. Mitsubishi publishes data were they have 100% heating capacity at -15C, which some models being 100% at -20C and -23C: * https://www.mitsubishielectric.ca/en/hvac/home-owners/zuba https://www.mitsubishielectric.ca/en/hvac/home-owners/zuba At -25C they have 80% capacity: * https://www.mitsair.com/wp-content/uploads/2024/10/MEM-202406-E_ZubaRebrandBroch_LR_FIN-1.pdf https://www.mitsair.com/wp-content/uploads/2024/10/MEM-20240...
- whateveracct 1y ago
  > What percentage of the (US) population gets temperatures like that? That's generally mostly IECC Zone 7 (though cold snaps in Zone 6) can happen: A lot? e.g. Chicago gets it every year
  - throw0101c 1y ago
    >>> Mine struggles if it gets below 30, and might as well not exist below 10. They're not great at low temps. >> > What percentage of the (US) population gets temperatures like that? That's generally mostly IECC Zone 7 (though cold snaps in Zone 6) can happen: > A lot? e.g. Chicago gets it every year [citation needed] Per historical weather data: https://ashrae-meteo.info/v2.0/index.php?lat=41.960&lng=-87.932&place=%27%27&wmo=725300 https://ashrae-meteo.info/v2.0/index.php?lat=41.960&lng=-87.... It is warmer than -16C/3F at Chicago (O'Hare) for 99% of the time (i.e., except for 4 days a year), and warmer than -18.7C/-2F for 99.6% of the time (2 days). ASHRAE are the folks that publish the heating/cooling standards that are used in building codes for estimate heating/cooling equipment capacities (Manual J) and selecting the right equipment (Manual S). Here's a PDF with a lot of locations in the US and CA (and other countries further down), and if you look under the "Heating DB" column, you'll find very few US locations that have -30F under the 99% (or even 99.6%) sub-columns: * https://www.captiveaire.com/catalogcontent/fans/sup_mpu/doc/winter_summer_design_temps_us.pdf https://www.captiveaire.com/catalogcontent/fans/sup_mpu/doc/... So unless you're in AK, MN, or ND, long runs of temperatures colder than -20F/-30C don't happen too often. Of course if you have a leaky house with little insulation, you're throwing money out the window/door, so the first consideration for a good ROI is better air sealing and insulation.

crgwbr 1y ago

That’s true, but still doesn’t always make heat pumps the most cost effective choice to operate. For example, last winter I paid an average of $0.24/kWh for electricity vs $0.05/kWh for natural gas. Even if a heat pump had a perfect 4.0 COP all winter, gas would be ~15% cheaper. Electricity prices really need to come down before it will be viable for everyone.

doctorhandshake 1y ago
Yeah. Sadly the trend does not seem to be heading that direction what with the current admin’s … policies and the whole … AI … thing.
kragen 1y ago
Get solar.
- crgwbr 1y ago
  I’ve tried. For it to be at all viable on my property, I’d need to cut down a bunch of trees. I’d rather keep the trees and pay someone else with solar panels.
  - kragen 1y ago
    That makes sense. Is that legal?
    - kragen 1y ago
      I mean, in many countries, often either the government or a company closely allied to the government has been granted a legal monopoly on selling electrical energy, so buying electricity from other people is illegal.
etimberg 1y ago
Not to mention, lots of places have time of use electricity pricing which makes it even worse. This is the problem with running my heatpump when its cold, some of the coldest times (right before dawn) coincide with peak time-of-use prices

sokoloff 1y ago

They have good heat output down to very low temperatures, but not good efficiency. The CoP is often around 2.0 at those very low temps, though (and of course the heat energy demanded is higher).