Plug-in Heat Pump Water Heater

I’ve been researching heat pump water heaters again after the success of getting a heat pump dryer. We used to vent, and waste the heat, from our natural gas dryer to outside, and now we reuse our heat and just pump some water down the drain.

Anyways, Menards’ (a big box hardware store in the Midwest) brand of water heaters is Richmond. On a form for certain energy reheated, it looks like Rheem makes the Richmond line since Menards doesn’t carry many brand names, like Rheem, much at all. Richmond has a 50 gallon, 15amp model, that would be a fairly 1-for-1 swap to our 50 gallon nat gas model. Since it’s 15 amp, it could even go on a smart plug.

I’ve been reading up on electric codes, and while it sounds like some southern states like Texas and Florida used to have plug-in water heaters, that is no longer a thing. Generally, codes seem to say that since water heaters are an appliance that doesn’t get swapped out often, you hard wire it in to a shut off switch. Of course there’s the argument to be made that an electric double oven doesn’t get swapped out often and that both plugs-in and isn’t wired to its own cutoff switch, but I don’t think one can argue with the NEC.

However, Rheem now makes an official plug-in 15 amp, 50 gallon, heat pump water heater. RHEEM® INTRODUCES 120 VOLT PROTERRA® PLUG-IN HEAT PUMP WATER HEATERS That press release specifically mentions California multiple times. I’m guessing that means California changed their electric and/or plumbing code to allow for a plug-in replacement model, but that seems to confirm that there’s no safety reason why a 120v heat pump water heater couldn’t be plugged in. Hopefully this means that more people can make the easier transition away from natural gas while also being able to glean exacting usage from their heat pump water heater.

I just thought I’d share that Rheem news as it was only announced 3 weeks ago. Here’s hoping that product line can make its way around the states.


Brian… We use a Rheem 40 or 50 gal…and is hard wire with, If I remember right… #10 wire. The mode I have been running it in only draws about 350 watts @ 220 volts. Runs about about 45 minutes to recover most times… Not long showers. It can be used like a ‘conventional’ upper/lower element type pulling 3500 watts. I have it tided to the solar system for the low wattage recover. Has a built in timer / temperature so you can have it go into recovery when the sun is high. Been working great…Didn’t want to muddy the waters… Gerry

I installed a heat-pump water heater and have been monitoring it with Sense since last fall.

It’s a great technology and I highly recommend it. I expect for a 110v/15amp water heater, you’d still need it on a dedicated circuit. So if you’re running a dedicated circuit already, I’d still recommend going with the 220v/30 amp versions.

The smaller backup heating element on the 110v version means that they’d have to program the resistive element to kick on much earlier. At least I assume this is what they do. You’d lose a decent amount of efficiency this way.

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Everything I’ve been reading says dedicated circuit, and I certainly agree with that. The issue is that I only have one unused breaker right now. I don’t want to use the two the Sense is on until I get an electric car, somewhere between next year and 20 years from now. By going with the 15 amp version, that’ll let me use 14 gauge wire instead of 8, and I’m going about 35 feet, maybe even more like 40 or 45 as I haven’t precisely measured it yet, and with wire prices, that comes out to $60 in savings just on wire. If I go 30 amp, I also need to run new conduit the same distance, whereas I can easily fit three more 14 gauge in some 1/2” conduit that runs nearby.

The specs for the 15 amp Richmond version (10E50-HP4D 694061) give me and my wife 53 gallons for the first hour, and 16 per hour after that. The 30 amp stats are 67 and 29 per hour. It’s just two of us, and a dog, right now, and we never run dishwasher, washer, shower, etc. at the same time. 53 gallons is plenty. There’s also a marginal savings on the unit itself. I’ll also need to install another basement drain as there’s no place in-room for the condensation to run, and Rheem says these units can make up to 2 gallons per day, so using a bucket sounds like a bad idea when I forget to check it for two days.

I had fun running the 220 for my new dryer, but I was going a much shorter distance through an open wall with only studs in the way. This is already a much more involved process, but one I’m confident I could do. Only sweat copper pipe once though and don’t have the proper tools there, so that could get interesting.

How are you monitoring your usage, through the unit’s app, DCM, smart plug, or some other way?

That makes sense. Your use-case seems to be what the 15amp version was trying to solve for.

And everything I’m writing on the 15amp version is me inferring what engineers might be doing based on my experience with the 240V/30amp AO smith version.

Sense detected my heat pump in about 30 days and the backup resistive units in about 60 days, so I’ve been able to be slightly obsessive in observing how it behaves.

The heat pump itself only draws about 425W when it turns on. So you could nearly fit 4 of those on a 15 amp circuit. It’s the backup resistive units that draw about 4,500W when they turn on that really suck down the juice.

I kept the temperature low on it when I first installed it for energy savings and because I have kids in the house. This meant that it mostly ran on the heat pump, but the resistive elements would kick on for 5-10 minutes if me and my wife showered back-to-back.

After talking with someone who professionally installs these, I turned the temperature up a few degrees. Now the resistive elements almost never kick on. This professional installer actually maxes energy savings by putting the temperature on them super high (like 150+), but installing mixing valves to reduce the temperature at the faucet. This pretty much guaranteed it would only run on the heat-pump and was counter-intuitively more efficient. I haven’t gone to those lengths, and don’t think I need to.

The place where the backup heating elements come into play is when we have house guests. By changing the mode from “efficiency” to “hybrid”, my water heater has been able to keep up with multiple house guests at the same time with no shortage of hot water. This is where the 15amp version will struggle to keep up.

One consideration I forgot to mention is the new reconciliation bill that just passed.

They have some major incentives for heat-pump water heaters, but I believe the incentives only apply if you have it professionally installed. Check the math for your use case, but it might actually be cheaper for you to pay someone to do it if you wait until 2023.

That’s a great point. I’ve been reading about how the bill has a lot of heat pump incentives, but since the bill isn’t law yet, hard facts and figures haven’t been the clearest. We had a small leak in our 13 year old nat gas water heater and had it replaced in April 2020, so unfortunately for me, this unit won’t NEED to be replaced for at least 8 more years when it’s warranty expires.

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I’ve started collecting the condensate & use it on plants or to fill bathtub. I guess I’m a cheap Yankee.

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here’s a pic of the $30 Menards exhaust duct adapter on an AO Smith heat pump water heater I installed. OEM kit is almost $400 & noisy metal instead of plastic. The conditioned air is pumped into the Man Cave. Simply turn set point to 101F if you can wait for hot water & want it quiet OR go to electric mode if you need it fast & quiet. Return set point to 135-140F when leaving; like turning off lights.
Great idea to use it as a heat battery & mixing valve! Also, consider a larger 80 gal. Gotta learn new habits for the new tech. Remember to insulate pipes.
I wouldn’t wait to buy an EV. I can find free charging stations. With a 120V water heater, you could run an extension cord if the EV has V2L or use a 1000W inverter (like RV) on the 12VDC & get free hot water or hot water during power outage. Hardwire the heater, then add an extension cord plug & recepticle. During outage plug heater into car; so pay attention to sequence. Transfer switch may be best for your house. Sense shows our AO Smith uses 341W.
Actually, I would price a used EV now but wait for January when a $4K rebate starts for used EV’s bought thru dealers. OTOH, I don’t know how to guarantee EVeryone will not go up by $4K in Jan…negotiate much?
Again, I can find free chargers (Plugshare, etc) so if I get 3mi/kWh, drive 48,000 miles, pay $0.25/kWh normally - I breakeven.