I’ve seen adds for a new GE heat pump based water heater. Energy Star rated and all that. I’m skeptical though. A heat pump takes heat from the environment and “pumps” to where it’s wanted – in this case, the water in the tank. That sounds great and would be if the heat was “free” from outside the house. But water heaters are located inside the house – normally in a heated area. So the heat pump takes heat from your house; uses it to heat the water in the tank; and then your furnace must replace the heat taken from the house. This seems really inefficient to me. Am I missing something?
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then your furnace must replace the heat taken from the house.
Part of the effciency assumes the HP WH will be in a "not too" climate controlled area like the basement or in an overheated area like the furnace room. The major gain, though, is in the cooling season. In the good old summer time, it'll be sucking the heat out of the house and spitting out cold air while providing hot water.
Well, it's not "really
Well, it's not "really inefficient", only "sorta inefficient". Makes a lot of sense in the south, where heat is free, less in the Frozen North. And it is more efficient than using resistance heating (in cases where it's impractical to use a gas WH), so long as the house heat source isn't horribly expensive.
As the other poster elluded to ... it depends on the climate. Your concept is right on, though. All the heat pump water heaters I've heard about draw the heat from e.g. an exhaust fan/vent (which presumably runs 24/7?? not sure).