3 ms·

> an air conditioner might move 3 units of heat using 1 unit of energy. So run that system backwards for heating, and you would at only use twice the energy fo

> an air conditioner might move 3 units of heat using 1 unit of energy. So run that system backwards for heating, and you would at only use twice the energy for heating. That said, you can typically cut your heating bill in half using ASHP, with it losing efficiency as the outside temperature decreases. It rarely goes below a COP of 1, so it makes sense to use in place of resistance heating. However that assumes that you must use electricity for heating. Using wood for heating, you are using a renewable resource that is cheaper for every unit of heat you get.

jandrese 8y ago
The downside of electric heat pumps is that they simply don't work when it gets too cold outside. They can't push the thermal gradient hard enough and end up switching to inefficient resistive heat. Go far enough north and even the resistive heat doesn't work very well and everybody uses gas.
- hvidgaard 8y ago
  When the correct gas is used, they are more efficient than resistive heating down to -20-30 C. Very few places in the world get that cold. That said, and as I mentioned, using wood or district heating, is far more common in those parts of the world. At least in Europe.
  - jandrese 8y ago
    Very few places, like all of Canada, parts of the northern US, Alaska, most of Russia, etc... Even then you have to be willing to keep the thermostat set at 55F/13C or the resistive heaters are going to kick in.
    - hvidgaard 8y ago
      I'm unsure if you know how cold -20C actually is. At -20C outside you can still get an efficiency of 2.0. The majority of Canada does not reach that temperature outside of a few cold spells. Only two handful of cities in Canada have nights with less than -30C. In other words, the majority of time it will be more efficient than resistive heating. The north or interior of Alaska is typical mainland climate and very cold, and same goes for Russia. In both countries a non trivial part are not that cold. The majority of the world are simply not so cold that resistive heating is better than an ASHP system. That is not to say gas isn't cheaper.

jandrese 8y ago

The downside of electric heat pumps is that they simply don't work when it gets too cold outside. They can't push the thermal gradient hard enough and end up switching to inefficient resistive heat. Go far enough north and even the resistive heat doesn't work very well and everybody uses gas.

hvidgaard 8y ago
When the correct gas is used, they are more efficient than resistive heating down to -20-30 C. Very few places in the world get that cold. That said, and as I mentioned, using wood or district heating, is far more common in those parts of the world. At least in Europe.
- jandrese 8y ago
  Very few places, like all of Canada, parts of the northern US, Alaska, most of Russia, etc... Even then you have to be willing to keep the thermostat set at 55F/13C or the resistive heaters are going to kick in.
  - hvidgaard 8y ago
    I'm unsure if you know how cold -20C actually is. At -20C outside you can still get an efficiency of 2.0. The majority of Canada does not reach that temperature outside of a few cold spells. Only two handful of cities in Canada have nights with less than -30C. In other words, the majority of time it will be more efficient than resistive heating. The north or interior of Alaska is typical mainland climate and very cold, and same goes for Russia. In both countries a non trivial part are not that cold. The majority of the world are simply not so cold that resistive heating is better than an ASHP system. That is not to say gas isn't cheaper.