Anyone have any thoughts on heat pump tank style hot water heaters?
Yeah. Buy one. Duct it to the hottest place in your house (if you've got an attic), or if you have a good thermally stable spot (basement), and go.
The little poking I've done seems to indicate that they are one of the most energy efficient styles, even compared to natural gas tankless. Another benefit in my eyes is that they would benefit from solar whereas tankless natural gas(the other most efficient style afaik) would not.
Correct, though if you're exchanging air with a conditioned space in a heating degree day dominated climate, the savings are a bit less than advertised as you're shifting thermal demand around. If you're cooling degree day dominated, you should have one yesterday, because they're literally just cooling your house and saving you gobs of money in the process.
They will use far less electrical energy than a resistive type (either tankless or tanked), and if you figure natural gas is maybe 50% from "thermal energy at the turbine" to "your heater," they still use half the primary energy of a natural gas heater. Plus, as noted, they can shift loads around to match solar and wind production.
I don't like tankless heaters. They require huge gobs of power any time they're running, and you can't shift that into better times of use like you can with storage type heaters.
Keeping 50+ gallons of water hot 24/7 seems like a large electricity cost and perhaps worth checking into more efficient options.
It's not. Go stand with your hand on the outside of your hot water heater for a while. Is it hot? Probably not. If you can even tell it's
warm, you might consider another layer of insulation, but most hot water heaters are very well insulated and don't leak much thermal energy.
On the flip side, you can heat the water when you have spare energy (if you have behind the meter solar), or just heat during grid slump times if you don't ("not morning showers" and "not evening dinner rush"). Most of them have schedules you can set.
A decent heat pump water heater in a not-too-cold area will use a quarter of the electricity of a conventional resistance heater water heater, saving hundreds of dollars per year.
Correct, but if you're heating water based on conditioned air from the building envelope, that heat has to come in from somewhere - be it your heat pump, natural gas, etc. You're saving money on the water heater, but you are shifting at least some costs elsewhere. However, during the summer, it's cooling the space, which is useful.
Be aware that most of them have a separate condensate drain from just the overflow, and those can't be merged, so you'll probably need to punch a new drain hole if there's no existing condensate line you can tap into.
I'll check back in when I find out what kind of water heater I'm going to have.
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