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We recently got a heatpump and... it feels like witchcraft. It chugs away even at 20F blowing hot air into our house.

by davidw 3y ago

Kye 3y ago
At 20F that's probably the backup heat kicking in. Heat pumps start losing their efficiency advantage around 40. edit: apparently I was misinformed, but it doesn't seem like something worthy of being downvoted into oblivion.
- davidw 3y ago
  No, because the installer set it up right at 20. We do have a gas furnace that kicks in below that. It'd be amazing if someone put together some kind of dynamic calculator that could take electricity and natural gas prices and examine inside temperatures based on a smart thermostat system and rejig the cutoff temperature based on all of it.
  - patmorgan23 3y ago
    Bet you could do this in home assistant
    - davidw 3y ago
      Yeah, if I could figure out the calculations to use and source all the data...
  - ZeroGravitas 3y ago
    There are hybrid heat pumps that do exactly this.
  - pjc50 3y ago
    My Vaillant system claims to do that, but it doesn't have dynamic input of pricing so you have to type it in on the head unit. I'm not sure it's even possible to get an API for dynamic pricing of UK energy prices.
    - bdsa 3y ago
      Octopus have a tariff with dynamic electricity pricing: https://octopus.energy/smart/agile/ https://octopus.energy/smart/agile/ There's a (third-party?) dashboard of the data here: https://agile.octopushome.net/dashboard https://agile.octopushome.net/dashboard
      - pjc50 3y ago
        46.73p per unit at peak time while the average is roughly equal to the regular tariff? That seems like a bad deal. Does make it very clear where the afternoon peak is though, and that's a nice dashboard.
- tempestn 3y ago
  Modern cold-climate heat pumps can definitely handle 20F. Yes they're more efficient at higher ambient temperature, but you can get at least 2.5 COP at 20F. (And good ones can continue to outperform resistive heating at much lower temperatures than that.)
- valenterry 3y ago
  Nope. The really good heatpumps (air conditioners) have a COP of 4 at -7 degrees celcius and a room temperatur of 20 degrees celcius. In other words, with one part of electrical energy, they manage pull 3 parts of of heat energy from the outside air into the room. Hence, they use just 25% of the electrical energy that a electrical resistance heater would require.

We recently got a heatpump and... it feels like witchcraft. It chugs away even at 20F blowing hot air into our house.

by davidw 3y ago

We recently got a heatpump and... it feels like witchcraft. It chugs away even at 20F blowing hot air into our house.

Kye 3y ago

At 20F that's probably the backup heat kicking in. Heat pumps start losing their efficiency advantage around 40. edit: apparently I was misinformed, but it doesn't seem like something worthy of being downvoted into oblivion.

davidw 3y ago
No, because the installer set it up right at 20. We do have a gas furnace that kicks in below that. It'd be amazing if someone put together some kind of dynamic calculator that could take electricity and natural gas prices and examine inside temperatures based on a smart thermostat system and rejig the cutoff temperature based on all of it.
- patmorgan23 3y ago
  Bet you could do this in home assistant
  - davidw 3y ago
    Yeah, if I could figure out the calculations to use and source all the data...
- ZeroGravitas 3y ago
  There are hybrid heat pumps that do exactly this.
- pjc50 3y ago
  My Vaillant system claims to do that, but it doesn't have dynamic input of pricing so you have to type it in on the head unit. I'm not sure it's even possible to get an API for dynamic pricing of UK energy prices.
  - bdsa 3y ago
    Octopus have a tariff with dynamic electricity pricing: https://octopus.energy/smart/agile/ https://octopus.energy/smart/agile/ There's a (third-party?) dashboard of the data here: https://agile.octopushome.net/dashboard https://agile.octopushome.net/dashboard
    - pjc50 3y ago
      46.73p per unit at peak time while the average is roughly equal to the regular tariff? That seems like a bad deal. Does make it very clear where the afternoon peak is though, and that's a nice dashboard.
tempestn 3y ago
Modern cold-climate heat pumps can definitely handle 20F. Yes they're more efficient at higher ambient temperature, but you can get at least 2.5 COP at 20F. (And good ones can continue to outperform resistive heating at much lower temperatures than that.)
valenterry 3y ago
Nope. The really good heatpumps (air conditioners) have a COP of 4 at -7 degrees celcius and a room temperatur of 20 degrees celcius. In other words, with one part of electrical energy, they manage pull 3 parts of of heat energy from the outside air into the room. Hence, they use just 25% of the electrical energy that a electrical resistance heater would require.