Post #1590248

2026-04-23 17:54 UTC

Theoretically you could use a heat pump to heat water that would generate “waste cold”, but heat pumps typically don’t get nearly hot enough to heat water as much as a gas water heater does. I suppose one could be made but it would be very difficult, I think. It would need to use the ambient air in your house and suck enough heat out of it to heat your water, and if your house is about 72°F / 22°C and you want water at 130°F / 54°C (which is pretty typical) that seems like a challenge, especially since water is so much denser and has a higher heat capacity. I have a portable A/C with a heat pump and it starts to struggle to heat my apartment once it gets down to 45-50F outside and it struggles to cool once it gets above 95F.

Replies (3)

@Draconic_NEO@lemmy.dbzer0.com 2026-04-23 18:05

GE currently sells a heat pump water heater on the market, I’m not sure if it uses resistive heating to supplement the heat pump I have a portable A/C with a heat pump and it starts to struggle to heat my apartment once it gets down to 45-50F outside and it struggles to cool once it gets above 95F. Your AC may be undersized if it doesn’t perform well in hot weather, also unfortunately many heat pumps aren’t optimized for extreme cold weather performance. Some are, it’s definitely not a failure of heat pumps in general, but you’ll only find those as permanent install units and they’re usually only sold up north.

Open ##1590811
@SapphironZA@sh.itjust.works 2026-04-23 19:16

Check if you can get some shade on your exterior unit. Also check that the area is well ventilated. And as always, insulation is king.

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@SapphironZA@sh.itjust.works 2026-04-23 19:12

Its all just about the relative compression ratio of the refrigerant. They make heat pump based water heaters that have external units that operate identically to air conditioners running in a heating mode.

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