Heat Pump water Heaters

[Shimmy]

For those of you with HPWH's already, using it in heat-pump only mode how do you find the recovery time? Our shower is a water hog-- something like 12 gallons per minute. Usually showers are very short (<3 minutes of running water), but some days they go longer and back-to-back showers are common.

Our current water heater setup is solar with a total of 240 gallons of storage, resistance backup heat on one of the two tanks that gets used maybe 10 days per year. (The house was built as an AirBnB and could hold 20 surfers.)

If I went with a HPWH the solar HW would need to go; I can fit 3.2kW of PV panels in the same space easily.

 

[DIYrich]

Running is 400 watts. Assuming 3x efficiency, that is an effective 1,200 watts. About 1/4 of a 5,000 watt resistance heating element. Mine ran almost all day (7 hours?) To do the initial heating of the 50 gal tank.

If I do the calculation right, it is about 7 gal/hrs to raise 60 degrees. Something like 50-60 gal first hour delivery rate. Heat to 145, and use mixing valve to reduce to 120.

It does have resistive heating element for faster heating.

 

[Zwy]

30% off $1699 is still $1,189. That's a far cry from the $300 I paid (after instant credits) in 2019 + I got something off my taxes. Either the price in 2019 was insanely low or someone is jacking up the price here in 2024.

Rheem Performance Platinum 50 Gal. 10-Year Hybrid High Efficiency Tank Electric Heat Pump Water Heater XE50T10H45U0 - The Home Depot

The Rheem ProTerra Electric Hybrid Electric Heat Pump Water Heater. Heat pump technology makes it 4X THE EFFICIENCY of a conventional electric model (of the same or similar capacity). More efficiency means more energy savings. It's so efficient, it can pay for itself in energy cost savings...

www.homedepot.com

View attachment 214358

You are forgetting inflation.

My business management system has a screen that pops up when entering in a vendor PO and invoice for a part number that was sold here before. Most items have increased by 45% since 2019, easily over 7% per year compounded.

The government lies about inflation. I finally figured out the true % increase per Kwh the utility is enacting over this year and next. The second year is compounded off the first year increase. It comes to 26% increase over those 2 years from last year.

$700 x 8% compounded yearly =$1028.53

$700 x 1.45 = $1015

That is the true rate of inflation since 2019.

 

[Zwy]

For those of you with HPWH's already, using it in heat-pump only mode how do you find the recovery time? Our shower is a water hog-- something like 12 gallons per minute. Usually showers are very short (<3 minutes of running water), but some days they go longer and back-to-back showers are common.

Our current water heater setup is solar with a total of 240 gallons of storage, resistance backup heat on one of the two tanks that gets used maybe 10 days per year. (The house was built as an AirBnB and could hold 20 surfers.)

If I went with a HPWH the solar HW would need to go; I can fit 3.2kW of PV panels in the same space easily.

Keep your solar water heater until it fails. Nothing is cheaper than something that is already paid for and running. 240 gallons is nice size, using a calculator for heat storage of 90°F to 130°F comes to about 23.5 Kwh. Heating water coming out of the ground at 55°F to 130°F is 44Kwh.

I figure 8 hours to fully warm up 50 gallon HPWH from about 55°F to 130°F. Compressor running is around 400W. Yes, I know the math doesn't seem correct with a COP of 3 to 4. It will depend on ambient temp where the water heater is located, COP is higher at lower water temp and higher room temp at the start due to Delta T. As the water heats up in the tank and room temp drops, the Delta T is lower and COP will drop.

 

[Rider]

Has anyone tried the AOSmith heat pump water heaters?

I've had one for a couple of years now. I run it solely in the heat pump mode, have never had to use the coils. Don't have details, but my electric use is down. No issues to date.

It's my understanding that AO Smith just puts their label on the heater, it's not "theirs".

 

[gotbeans]

They do, stainless and abs.

Not cheap, I bought a lifetime plastic tank water heater for a rental, about double the price.

I wouldn't want ABS for my water
I have had a PTF...E? 300 gal tank for like 15 or 20 years and it works fine, cost $200.

Hot water tanks in the UK are copper, I never heard of one leaking, ever.

yep, pretty nice

 

[Zwy]

I wouldn't want ABS for my water
I have had a PTF...E? 300 gal tank for like 15 or 20 years and it works fine, cost $200.

PTFE: PFAS

PFAS is known as one of the forever chemicals. EPA has been shutting down farms that applied sewage sludge containing PFAS.

 

[Madcodger]

PTFE: PFAS

PFAS is known as one of the forever chemicals. EPA has been shutting down farms that applied sewage sludge containing PFAS.

I live in the epicenter of the PFAS problem, in rural Maine. This whole issue with PFAS started (basically was discovered) here because years ago the state encouraged farmers to take sludge as a great source of fertilizer. It isn't really the US EPA that's "shutting down" farms, so much as some of the farmers themselves (people love to blame the govt, but in this case, they're actually a little bit behind on the issue). In fact, EPA only recently revised their PFAS limits (much lower). PFAS contamination will likely be a much bigger problem all over the US in coming years, as the effects of PFAS chemicals are just becoming more widely known. As you note, fields that have been fertilized with sludge are the big problem, and there are a lot of them.

 

[kendive]

A tank type water heater is an energy storage device, just like any battery. A HPWH is a smart appliance that can be programmed with an app or home energy management system to run only at times of cheap electricity or excess solar production. I originally wanted to install a dump load for excess electricity available from PV and decided to buy a hybrid HPWH instead of heating element only water heater.

The HPWH is so efficient it really isn't a dump load, I just let it run all the time. Come winter, with the HPWH ahead of the propane water heater, I can use the propane during extended periods of low PV production.

Yea our elec rate all in is about .12 to .13 kWh.

I also have an off grid cabin and anything heat related is propane.

 

[gotbeans]

PTFE: PFAS

PFAS is known as one of the forever chemicals. EPA has been shutting down farms that applied sewage sludge containing PFAS.

luckily that isn't PTF/E
Looks like some relation to teflon (PTFE) for your PFAS though

and my jug is PET / PETG lmao damn acronyms..

 

[Gold Country Russ]

I'm thinking that I will leave my propane water heater as is and install a modified electric water heater as a preheater. I would use the existing water heater thermostat to control the coil of a high voltage DC contactor fed with either 116VDC @1,200W or 155VDC @ 1,600W from 3 or 4 panels. Will select optimal heater element ohms to match the PV voltage. By running the dishwasher and washing machine in the afternoon and evening showers the propane heater would seldom fire. 1,600W X 3.41= 5,456BTUH or about 10GPH of water heated 65degF (60-125F), so by noon or 1PM plenty of water all afternoon. Not counting the panels (I have extra) or electric water heater (free or Craigslist bargain) it might cost a couple of hundred dollars which equals something like buying 50 gallons of propane.

 

[SilverState]

Question for folks about HPWH with the heating element (non heat pump / hybrid). I was planning on using the "smart load" / excess-power-dump feature of my all-in-one inverter to put excess power into the hot water. But that means that sometimes (often) the hot water heater might want to use the resistor but the inverter won't be powering it. Does this cause a problem / fault?

Like at 0300 in the morning if the heater is looking to run the resistor it won't be powered on, but it most likely will at 1400 the next afternoon.

I know the Rheems want to see power on that resistor at startup just as a systems check, that should be easy enough because I just can boot up the Rheem when there's excess solar.

Just curious if any of you have played with that.

 

[Gold Country Russ]

My opinion, HPWH is a great concept, however so far, the physical executions are short of wonderful. I will wait for the equipment designs to mature and prices to drop before purchasing.

 

[SparkyJJO]

My opinion, HPWH is a great concept, however so far, the physical executions are short of wonderful. I will wait for the equipment designs to mature and prices to drop before purchasing.

If the current regime has their way, you'll be forced to buy one if your tank fails and you need a new tank, whether things are mature or not.
Yes, they're coming for our water heaters now

 

[Zwy]

Question for folks about HPWH with the heating element (non heat pump / hybrid). I was planning on using the "smart load" / excess-power-dump feature of my all-in-one inverter to put excess power into the hot water. But that means that sometimes (often) the hot water heater might want to use the resistor but the inverter won't be powering it. Does this cause a problem / fault?

Like at 0300 in the morning if the heater is looking to run the resistor it won't be powered on, but it most likely will at 1400 the next afternoon.

I know the Rheems want to see power on that resistor at startup just as a systems check, that should be easy enough because I just can boot up the Rheem when there's excess solar.

Just curious if any of you have played with that.

Smart water heaters can be programmed for time on/off. If you don't want the water heater to run during the night, you can program it to not run. Do not cut power to the unit, it isn't needed. Just program it to run during the day.

I turn my HPWH off at night when there is bad weather for several days. Doesn't affect the temp if you want to take a shower in the morning but I do have the 50 gallon propane in series so 100 gallons of hot water. I do have a thermostatic shower valve.

After owning a hybrid heat pump water heater, I would not choose any other electric water heater for my personal use There is the choice of heat pump and element (high demand) or only heat pump. Plus Eco mode.

 

[Zwy]

My opinion, HPWH is a great concept, however so far, the physical executions are short of wonderful. I will wait for the equipment designs to mature and prices to drop before purchasing.

HPWH have been around for some time, it is mature. More than 10 years.

As for prices, until the 30% tax credit for energy efficiency is done, you won't see much price drop. With inflation, the same water heater might cost 150% of today's prices 2 years from now. Take a look at what just an electric hot water heater costs today compared to 2, 5 and 10 years ago.

I found my heat pump water heater to be one of the best additions to my solar system along with the mini split heat pumps for heating and cooling.

 

[SparkyJJO]

I just have a hard time spending 3x as much for something much more complicated, that has no guarantee of lasting any longer than the very simple tank.

 

[Zwy]

I just have a hard time spending 3x as much for something much more complicated, that has no guarantee of lasting any longer than the very simple tank.

Then why are you reading this thread?

As for cost, this was my payback period. And my water heater was gas.

 

[SparkyJJO]

Then why are you reading this thread?

As for cost, this was my payback period. And my water heater was gas.

Because I'm still curious lol

 

[Zwy]

Because I'm still curious lol

I debated for some time about just installing an element unit for a dump load or the heat pump unit. I decided with the hybrid I could choose whatever way I wanted. I have yet to use the element, the unit is just that efficient. Come next winter, I might use the element more as I will want to dump power on nice days.

The heat pump units are so much more efficient compared to an element heater. Conservation always pays, using more efficient appliances not only reduces system size but allows for a smaller battery bank or adopting more energy efficient appliances to use the power saved. No different than changing from a resistive heater for heating a home compared to using a heat pump. My goal for my home is 100% off grid. I'm close at less than 3% from grid in the last year while increasing yearly Kwh by moving towards more electric from gas.