shopping 120v hybrid hot water heater – looking for feedback on brands
CHenergy
| Posted in General Questions on
Hello:
Wondering if anyone has experience with 120v hybrid hot water heater installation. I’m also looking for advice with comparing brands – Rheem vs. AO Smith etc.
Thank you-
Chris
Minneapolis
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Replies
I don’t own one but from what I read the Rheem has a slightly higher COP so it should use less energy but there have been complaints of excessive noise with the Rheem units.
Note there are 290 post in this noise thread but not any new complaints so maybe some resolution.
https://www.greenbuildingadvisor.com/question/rheem-hybrid-water-heater-noise
Are you upgrading an existing gas water heater and trying to avoid adding a 240 volt circuit?
Walta
Hi Walta
Thanks -
Yes, exactly. Plus My household usage is not that much, so in theory 120v hybrid should suffice.
The HPWH in my house is 240V, though I did attend a webinar on 120V HPWHs last fall that included presentations from AO Smith and Rheem. There are some differences that may or may not be relevant to you:
AO Smith: top connections; 450 ft3 minimum room volume; electric resistance only used when HP is outside temp range (e.g., cold garage); easy to wire to a safety switch on a condensate pump (if a gravity drain isn't available)
Rheem: Two models: dedicated circuit w/o mixing valve (designed to replace a tankless unit that had a dedicated 120V outlet) or shared circuit w/mixing valve.
Both have 1-ton compressors (~800W nominal draw), where the 240V counterparts have a half-ton compressor. If you can install a 240V model, there are several advantages, including higher efficiency and smaller tank size (with the same first-hour rating).
Unless you are really really out of slots in the box, like all of them are already split 120 volt breakers, I would go 240. It takes no more wire.
Personally, I care about resiliency. Not having hot water quickly becomes a very acute problem in the sense that rather than fixing it the best way, you end up fixing it the quickest way.
A HPWH with 240V resistance elements is a serviceable water heater on its own, even if the heat pump breaks (which is most likely). A 120V unit is less so.
Unless there is a serious externality requiring a 120V HPWH vs a 240V HPWH, I would not install the former as the sole source of hot water.
I'd rather have my HPWH degrade into an adequate resistance unit than it become relatively useless.
I did get a quote for the 120 volt AO Smith. If you’re in the north I don’t even think you can get the Rheem 120 volt as it has no resistance heating elements so suppliers may not carry it. The only reason I considered a 120 volt is the ability to run it off a generator. If this is not a concern 240 volt is really the way to go as the heating elements are more efficient.
> this is not a concern 240 volt is really the way to go as the heating elements are more efficient.
I don't understand how they would be more efficient. Resistance heating is 100% efficient by definition.
As far as I know, the heat pump part of the heat pump water heaters is exactly the same on 120V and 240V models from the same manufacturer.
The heat pump compressor draws far less power than the backup resistance heating elements, typically about 700-800W while operating, far less than even a 120V outlet can provide.
My guess is if someone is on this web site and has a HPWH there is a 90% chance it is set to heat pump only mode making the element almost irrelevant.
The 120V model is designed for a growing market niche of people removing gas appliances and replacing it with a HPWH. The 120V unit will generally plug into an existing outlet without rewiring and happily share the circuit with other loads avoiding costly panel upgrades.
Walta
Thanks Walta
Electrification is the one of the main reasons I want to go 120 V HPWH and of course avoid a panel upgrade
A less often considered reason to go with a 120V HPWH or a 15A 240V (vs typical 30A models) is if you want to put it behind a battery backup system, which sometimes peak at 20A output current in the most common configuration.
Of course you trade off recovery time.
Alternatively you could stack more batteries to boost the current.
Great point Danan-
, I am hoping to go w a batt stystem in as soon as 5 years-, thinking positively- as soon as higher eff perovskite panels come to market.
David Roberts Volts podcast has a good podcast on this
I think in 5 years even the smallest residential batteries (5kWh) will do 32A (they do 16A today) , so you should be fine with a 240V in that case.