Case Study: Heat Pump Water heaters are great!

Using IOTAWATT I was able to validate the power savings of a heat pump water heater vs conventional.

It saves about 180 kWh of energy per month and reduced my monthly power bill by $23 , while also dehumidifying and cooling the garage by 5% RH (Relative Humidity) and 2 degrees F.

I have a bunch of pretty pictures and graphs in my personal project website. Reach out with any questions.

The next test/study I’m going to do is ducting the unit so it circulates air in the garage better, as well as adding insulation to the garage door and roof and measure the deltas.


I’ve had a Hybrid one since 2018, I love it. I only ever run it in heat pump mode (350-450w vs 5000w). I think they are making some now that only require a normal 110v outlet and only have the heat pump. Mine is a Rheem Hybrid and needs a 30A 240V which wasn’t a big deal because I replaced a conventional electric model.

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I have one too and while I think the technology shows promise, they are not without their issues. Many of the early GeoSpring ones failed early. I bought the AO Smith one from Lowe’s a little over 5 years ago. The heat pump failed this year. They were good about providing a replacement unit (whole water heater). If the replacement lasts a little over 5 years that will be just over a total of 10 years. I kept my original electric water heater (since it had a lifetime warranty) and it is still working fine at 17+ years. I bought the HPWH as backup to deal with the eventual failure of my original regular electric one. Luckily I had both so there was no rush when the HPWH failed. I was able to take my time to deal with the manufacturer and Lowes to get the warranty replacement unit home and installed.

If definitely saves money in the summer. In the winter it likely steals some heat from the furnace and house, so not as efficient (but likely more so than straight electric resistance).

Since I have a recirculation pump for instant hot water, I save about 10KWh/day. That means the savings paid my initial cost within 3 years. But, they are much more expensive now, unless you qualify for the really good rebates. Just don’t expect them to last 20+ years. They will likely last 10 years, but might need a warranty replacement (where you have to pay for labor) to do that.

I have a Rheems 50gal heat-pump hot water heater from Home Depot - was only $350 or so after rebates in Feb 2020. I run it in heat-pump only mode which maxes out at 400w and we’ve been averaging 166kwh/month power consumption. Low of 138kwh/month in summer and hi of 202kwh/month in winter.

We have ~150ft of hot water circulation for ‘instant hot water’ at the bathroom taps (loose efficiency due to this) and it’s under the house with 55F low ambient in winter and 75F hi in summer which is not optimal temps for heat-pumps but it still works very well.

We’re 3.5yrs in… hope it continues for a lot longer as they are $1700 now (crazy prices) :slight_smile:

BTW - Oregon defines ‘lifetime warranties’ as 7 years by law - did you know that? We found out the hard way on a LazyBoy chair.

Mine is about 5.5 years old, also purchased from HD, also with rebates but was ~$500. Still waiting for a temp sensor to go and take the whole thing out, but fingers crossed.

We’re averaging 48kW/h per month.

Interesting that this summer doesn’t have the dips that last simmer did. Might be because I changed the setpoint from 120F to 130F but don’t remember if it was around that time or earlier, and the other cause might be that we’re not keeping the one closet door propped open slightly like we used to. It’s in a closet with a normal door on one end and a pocket door on the other that’s usually open.