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my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 day

my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 days. He is discovering that electric heat uses massive amounts of electricity and there is no way to get a residential generator big enough to power them all. He might not even be able to power one (they can use in excess of 20kw). I would never get electrical water heater, stove, and heater for that reason.

boringg 4y ago
So this is one of my big concerns - I live in a cold weather country currently. We have power outages once every couple of years. If I don't have back up power my pipes freeze and then i'm out probably > $50k. I was thinking the solution for me is to put in a heat pump and then run a backup gas generator. But that solution feels like a significant amount of overbuild. I have 3 minisplits already but they aren't valuable in the winter -- where you install your AC units isn't where you would install your heating units .. I.e. the top of my house for AC, the bottom of the house for heat. Having multiple energy sources to defray risk is helpful.
- bluGill 4y ago
  Heat pumps are great when things are mildly cold. While do work down to -20C or so, efficiency drops off, so you need bigger and bigger units. It often makes sense to have a smaller heat pump that will only work down to -5C (random temperature, a real analysis of your house is required to give a better answer), and then a gas furnace backup for those really cold days. Once you have the gas furnace backup you can run that off of a small generator on the few days you are without power.
thekingshorses 4y ago
If there is a power outage, you can't run your natural gas heater either. It needs fan to run.
- triceratops 4y ago
  But you can run a furnace fan off a diesel generator.
  - p1mrx 4y ago
    Why diesel? If you need natural gas to run the furnace, it might as well run the generator too.
    - triceratops 4y ago
      Maybe "fossil fuel powered generator" would've captured better what I meant.
danans 4y ago
> my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 days. He is discovering that electric heat uses massive amounts of electricity and there is no way to get a residential generator big enough to power them all. He might not even be able to power one (they can use in excess of 20kw). If he's building the house new, he should strongly consider investing in designing the building envelope in a way that 20kW heat pumps aren't required. It's very possible, especially with new builds. The models to follow are Passive House [1] and Pretty Good House [2]. There are many examples of large houses built to those standards in cold climates that use a heat pump that only draws 2kW, which could easily be powered by a generator or backup battery. This assumes that by "big house" we mean something still below ~3500sqft and not some kind of mansion. The basics are to get the building air leakage below 1ACH50 (3-5x better than most codes, but not hard in a new build), and eliminate thermal bridging by using thick exterior insulation around the building perimeter. 1. https://passivehouse.com/ https://passivehouse.com/ 2. https://www.prettygoodhouse.org/ https://www.prettygoodhouse.org/

boringg 4y ago

So this is one of my big concerns - I live in a cold weather country currently. We have power outages once every couple of years. If I don't have back up power my pipes freeze and then i'm out probably > $50k. I was thinking the solution for me is to put in a heat pump and then run a backup gas generator. But that solution feels like a significant amount of overbuild. I have 3 minisplits already but they aren't valuable in the winter -- where you install your AC units isn't where you would install your heating units .. I.e. the top of my house for AC, the bottom of the house for heat. Having multiple energy sources to defray risk is helpful.

bluGill 4y ago
Heat pumps are great when things are mildly cold. While do work down to -20C or so, efficiency drops off, so you need bigger and bigger units. It often makes sense to have a smaller heat pump that will only work down to -5C (random temperature, a real analysis of your house is required to give a better answer), and then a gas furnace backup for those really cold days. Once you have the gas furnace backup you can run that off of a small generator on the few days you are without power.

thekingshorses 4y ago

If there is a power outage, you can't run your natural gas heater either. It needs fan to run.

triceratops 4y ago
But you can run a furnace fan off a diesel generator.
- p1mrx 4y ago
  Why diesel? If you need natural gas to run the furnace, it might as well run the generator too.
  - triceratops 4y ago
    Maybe "fossil fuel powered generator" would've captured better what I meant.

danans 4y ago

> my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 days. He is discovering that electric heat uses massive amounts of electricity and there is no way to get a residential generator big enough to power them all. He might not even be able to power one (they can use in excess of 20kw). If he's building the house new, he should strongly consider investing in designing the building envelope in a way that 20kW heat pumps aren't required. It's very possible, especially with new builds. The models to follow are Passive House [1] and Pretty Good House [2]. There are many examples of large houses built to those standards in cold climates that use a heat pump that only draws 2kW, which could easily be powered by a generator or backup battery. This assumes that by "big house" we mean something still below ~3500sqft and not some kind of mansion. The basics are to get the building air leakage below 1ACH50 (3-5x better than most codes, but not hard in a new build), and eliminate thermal bridging by using thick exterior insulation around the building perimeter. 1. https://passivehouse.com/ https://passivehouse.com/ 2. https://www.prettygoodhouse.org/ https://www.prettygoodhouse.org/