Hybrid hot water heaters

[ecofriendlycheapass.com]

I wanted to share results from our first full year with a Rheem hybrid (heat pump) hot water heater.

Our family of 3 with zero conservation efforts used 729kwh last year for hot water. Yes that’s under $70 in my market, saving $300-400 annually compared to a conventional electric tank.

My tank was $1550 and a $500 utility rebate, so great ROI!

[Jim @Emporia]

Awesome! @ecofriendlycheapass.com Thanks for sharing.

[MP-Ranger]

After installing solar in 2018 we started looking at Sense, which we started this energy journey with and found after Central HVAC water heating was the second most expensive thing we did here. We chose to migrate to LP gas using the tankless Rennnai whole house propane water heater and installed in the barn kitchen an Eemax ‘point of use’ 240VAC electric water. The combined electric savings of making this change paid for the new water heaters in just 16 months! So, I highly recommend the point of use and propane as the alternative to electric tank water heaters. To maintain a tank temperature all day for use when you shower once at night and do laundry every three days…. well, you see the point.

[ecofriendlycheapass.com]

Optimal for cost definitely varies a lot by region. What’s your cost of propane?

[ShieldSean]

Youtuber Technology Connections has a series of video’s about the difference in electrical efficiency between resistive heating  at 100% and heat pumps which can be in the 500% range. We recently moved to a more rural location that has only electric, where as previously we’ve had natural gas for the water heater and furnace. While our heat and AC are on the same reversible heat pump, unfortunately the previous owners only got a resistive unit for the water heater. Having just gotten my Vue installed yesterday I spotted our water heater using 5kw for a brief while after our first shower. Obviously I don’t have enough data to make a blanket statement about it’s usage over time in comparison to other uses, it didn’t take long for it to jump to the #3 circuit in that one use. The jury is still out if the entertainment center or my gaming workstation will use more over time. You can bet however that we’ll definitely be investing in a heat pump water heater when this one dies.

[dheatherly]

@ShieldSean don’t wait for your tank to die.  Get it out of there and replace it with a heat pump water tank – we use the Rheem mentioned in the top post.  Our hot water energy usage (previously had what was called an ‘efficient’ tank) went from a strong #2 (around $30/mo) to an also ran among things like our fridge (now using about $7/mo).  The savings are crazy.  There’s a fed tax rebate and lots of power companies offer rebates as well.  Our ROI time was more or less a year with the rebates.  The warranty on the Rheem is 10 years.  Do it.  Don’t wait.

[JimiH]

I’ve been thinking of a HP water heater for some time. You just tipped the scale. I’m pulling the trigger. Thanks

[Phase]

Situation: EU country, 2 adults in a (corner) house with thermopane glazing and isolated brick walls, we use 3,4 MWh electricity and 1400m3 natural gas yearly. Old PV generated 2,4MW yearly so we had to buy 1MWh from the grid

Had installed an additional 6,4kWp East/West PV (extra to the 2,4kWp South we already had for 6 yrs), so now we have 8,8kWp East/South/West orientations. This will generate yearly 6,59MWh, so we than have 3,19MWh spare Netto costs per 1 kWh is €0,06

For this energy surplus, i installed a 80 Liter heatpump boiler with a SCOP 2,34

To heat a traditional boiler of 80 L water from 13deg. to 55deg. celsius, takes 4 kWh electricity bought from the grid = 4 x €0,40/kWh = €1,60

4 kWh / 2,34  = 1,709kWh x PV €0,06 = €0,10

Now I don’t know what the COO and lifespan for this new heatpumpboiler is, so no costs taken in account for that, but it won’t be a factor 16 !
and on top of that, i made valves in the air intake and exhaust, so i am able to have the cool exhaust as airconditioning for the top floor

 

[Phase]

Situation: EU country, 2 adults in a (corner) house with thermopane glazing and isolated brick walls, we use 3,4 MWh electricity and 1400m3 natural gas yearly. Old PV generated 2,4MW yearly so we had to buy 1MWh from the grid

Had installed an additional 6,4kWp East/West PV (extra to the 2,4kWp South we already had for 6 yrs), so now we have 8,8kWp East/South/West orientations. This will generate yearly 6,59MWh, so we than have 3,19MWh spare Netto costs per 1 kWh is €0,06

For this energy surplus, i installed a 80 Liter heatpump boiler with a SCOP 2,34

To heat a traditional boiler of 80 L water from 13deg. to 55deg. celsius, takes 4 kWh electricity bought from the grid = 4 x €0,40/kWh = €1,60

4 kWh / 2,34  = 1,709kWh x PV €0,06 = €0,10

Now I don’t know what the COO and lifespan for this new heatpumpboiler is, so no costs taken in account for that, but it won’t be a factor 16 !
and on top of that, i made valves in the air intake and exhaust, so i am able to have the cool exhaust as airconditioning for the top floor

 

[Phase]

 

The 8 sensors i used for the logging of the electricity, were all used for other groups, so i now only can see the energy consumption in the “Balance”

• This reply was modified 1 year, 7 months ago by Phase.

[Freniata]

This month June will be my biggest water heater consumption to date.
We have a 2 tier usage system in Quebec
First 40KW/day is .07c/KW
Anything over 40KW/day is .10c/KW

In the last year my average is .09c/kw

This month after 27 days I have consumed 129.5KW so I’m estimating using about 144KW by end of month

My cost will be 144 x .09 = $12.96 or x 12 months would be approx $155.52. (It’s less than that for sure in my case)

It is absolutely not worth it for me to buy a Hybrid water heater.

[just1moredave]

We had a Rheem 50 gallon hybrid unit installed a couple of months ago and I like it. One important point for energy monitor customers, the Rheem app tells you how many kilowatt hours it uses, so you can save some sensors for other uses. We used to use 9 therms a month for hot water, now it’s less than 60 kWh. It might go up a bit in the winter as it is extracting heat from a colder basement.

At our energy prices (Colorado), it’s a little cheaper to run on electricity but not a lot. Electricity prices are less volatile, while gas costs spiked last year, but came down again. My guess is I would save maybe $5 a month, a long payback period. But energy costs are not the only costs.

In my case, the water heater was my last gas appliance so I can disconnect gas service and save $13/month. Professional installation added to the cost. Rebates make it cheaper. I have solar so my electricity is cheaper than market rates. My gas water was going to dissolve at some point. Carbon impact. The spreadsheet can be quite long. And I remember when appliances and cars didn’t have a payback period.

[Author]

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