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How do most people heat water with solar panels and batteries?

Heat pumps four to six times more efficient just takes longer so if you're running off solar all day it'll heat that water up so go for the bigger quantity.

It is a huge efficiency gain, no doubt about that.

And it'll cool the room off that he's got to come from somewhere You're just providing energy for it to transfer heat from the room to the water heater.

Which is great in summer plus it removes humidity, no dehumidifier needed. Win win.

So here in South Florida that's not an issue but what happens when you're up north in the winter?
That is why you purchase a hybrid, the element can always be used. Having said that, even in -20°F weather this winter, it never got below 50°F in my uninsulated basement. One thing about cold weather like that, the sun is shining and panels can really produce over rating. I have an electric radiant heater in the basement on a Shelly smart plug and would run it from 6 AM until about 8 PM using 800W. The inverters, batteries, charge controllers and one freezer along with the propane water heater and heat pump water heater help. The furnace does have a small outlet for some heat down there and with the radiant heater running, the floor upstairs is warmer. This summer the sill will get spray foam now that I'm done punching holes for PV wires and mini splits. That should help.

I thought of using the element but didn't see the need. If it hits -30°F, I might use the element. Using the heat pump allows me to use that power for something else like heating the actual living space.
 
And the 120v units draw about 500w on one leg. Not huge.
Good point. I don't think the 120V have the element, I always like options. My Richmond takes about 300W running, possibly some efficiency running on 240V?
 
AO Smith has a 900 watt element (120v) for if the compressor does not function such as too cold.
 
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With sufficient hot water storage it doesn't need to.

Good heat pumps will deliver ~ 4 times the heat power as they draw in electricity. Here the CO2 models deliver 5-6 kW of heat and draw ~1-1.2 kW of electrical power.
I used to think so too, until I own one. Granted, I have mine in energy saver mode, but still, 2 consecutive showers plus some light manual dish washing completely drain my 50 gallon tank. Good thing is I get more than half a tank of hot water after 30 minutes, but I can imagine a bigger household having problem with a 50 gallon tank running in 120V. If I set my tank to the quickest heating mode, I would probably never have to worry about running out of hot water with the 240V resistive heating element present in my heat pump water heater.
 
Granted, I have mine in energy saver mode, but still, 2 consecutive showers plus some light manual dish washing completely drain my 50 gallon tank
How long are your showers? What sort of flow rate?

50 US gallons of water heated from 12°C to 60°C requires ~ 10.6 kWh.

50 US gallons at 60°C should provide ~ 86 gallons of water at a shower temp of 40°C (assuming cold water supply is 12°C). At 7 litres/minute flow rate that's 46 minutes of showering.

50 gallons (189 litres) would be considered on the small side as far as tanks go.
 
How long are your showers? What sort of flow rate?

50 US gallons of water heated from 12°C to 60°C requires ~ 10.6 kWh.

50 US gallons at 60°C should provide ~ 86 gallons of water at a shower temp of 40°C (assuming cold water supply is 12°C). At 7 litres/minute flow rate that's 46 minutes of showering.

50 gallons (189 litres) would be considered on the small side as far as tanks go.
No idea, I got into the shower after my wife and niece finished theirs, to find only cold water coming out of the pipe. Checked the app, and it showed the tank's hot water was empty. I would say 50 gallon is average, at least where I live. The previous tank installed before I bought the house (3 bed 2 bath) was a 40 gallon.
 
No idea, I got into the shower after my wife and niece finished theirs, to find only cold water coming out of the pipe. Checked the app, and it showed the tank's hot water was empty. I would say 50 gallon is average, at least where I live. The previous tank installed before I bought the house (3 bed 2 bath) was a 40 gallon.

Set the water temperature higher. I switched from 120F to 125F and that helped.

On draining the tank.

Well, 2 females.. I live with the same setup
One takes a shower until the water-proof phone runs out of battery, or tik tok runs out of videos. Something like that.

I gave her a great looking (used) shower head (with flow activated lights) that has so many calcium deposits. It is under 1G/min.

They both use that water saver shower. It's actually the best bathroom. Or the 2nd best.

And still, they managed to drain the tank.
 
Set the water temperature higher. I switched from 120F to 125F and that helped.

On draining the tank.

Well, 2 females.. I live with the same setup
One takes a shower until the water-proof phone runs out of battery, or tik tok runs out of videos. Something like that.

I gave her a great looking (used) shower head (with flow activated lights) that has so many calcium deposits. It is under 1G/min.

They both use that water saver shower. It's actually the best bathroom. Or the 2nd best.

And still, they managed to drain the tank.
I actually have mine set to 122 (I just like that number) for the winter, and 125 for summer. My daughter is 4 now, soon it will be a 3-female household. It feels like they spend more time in the bathroom than any other room in the house :fp2 I swear, sometimes I'd have to pee outside because both bathrooms are occupied. No having to do a number 2 out there yet, knock on wood!
 
We have gas tankless on demand hot water heaters. One is at and of life. Considering options.
Do most people with solar install big 240v tank hot water heaters?
Or do they do on demand tankless electric hot water heater for whole house?
Or do people do smaller 120v point of use on demand tankless heaters?
Or what about the 8 gallon point of use hot water tanks?

When I look at some of the specs they all seem to use a lot of power, but the big tank ones at 4.4kWh seem to be the most. That’s like a day of production for me right now.

I’d prefer to do 120v stuff vs 240v if possible.
I have 3kw water heater I use 5.5kw inverter tied to batteries only to operate it since October, the 18kpv charges the batteries from 22panels.
it has been running great wit some grid charging for the 55kw batteries I have i will need to add more panels since i have them cover 2 houses.
 
No idea, I got into the shower after my wife and niece finished theirs, to find only cold water coming out of the pipe. Checked the app, and it showed the tank's hot water was empty. I would say 50 gallon is average, at least where I live. The previous tank installed before I bought the house (3 bed 2 bath) was a 40 gallon.
I set my heat pump water heater at 137°F. It has to go thru the propane water heater and that tempers it somewhat. Usually as I take a shower, the water temp increases as water from the heat pump water heater flows into the propane tank.

Usually when one wants a little more capacity, tank temp is raised and a tempering valve added. This allows the hot water to last much longer.

As for the app showing empty, I have found using just a small volume of water the hot water level indicated would drop from full to 1/3 fairly quickly so I wouldn't put too much faith in the app indicator.

If you have an anti scalding shower valve, then start turning the tank temp higher. Add a tempering valve or another water heater in series after the heat pump water heater like my setup.

Lastly, you could always put a timer valve on the hot water line. Set for 3 minutes and after that it is cold water only. I'll bet you will find the bathrooms won't be occupied all the time either. :ROFLMAO:

I don't know if such a device exists but maybe it should.
 
I set my heat pump water heater at 137°F. It has to go thru the propane water heater and that tempers it somewhat. Usually as I take a shower, the water temp increases as water from the heat pump water heater flows into the propane tank.

Usually when one wants a little more capacity, tank temp is raised and a tempering valve added. This allows the hot water to last much longer.

As for the app showing empty, I have found using just a small volume of water the hot water level indicated would drop from full to 1/3 fairly quickly so I wouldn't put too much faith in the app indicator.

If you have an anti scalding shower valve, then start turning the tank temp higher. Add a tempering valve or another water heater in series after the heat pump water heater like my setup.

Lastly, you could always put a timer valve on the hot water line. Set for 3 minutes and after that it is cold water only. I'll bet you will find the bathrooms won't be occupied all the time either. :ROFLMAO:

I don't know if such a device exists but maybe it should.
Here is a link to a test report on the rheem heat pump water heaters.

https://ecotope-publications-databa...essment-of-Rheem-Generation-5-Series-HPWH.pdf

We have the 240v 50 gal model, I got it for a good price, though if I was paying full price I would have gone with the largest version.

It helps reduce the humidity in my basement.

Time will tell how long the compressor lasts but it does significantly reduce my energy usage and the power requirements are so much less that I should easily be able to run it on generator or inverter power.

I don't know that I would replace a gsa WH with a heat pump if I had it but the HPWH is a useful thing.
 
This is top of mind for me as well. Currently have a 4500w 40gal resistance heater that shows up in my load graphs around every 60-90 mins all day long.

I've thought long and hard about these hybrid heat-pump water heaters. Here's my problem:

1) in 40yrs of home ownership, I've had water heaters fail and in all cases, it's the tank that fails. Not the heating mechanism. I can replace my electric hwh for around $400. Or I can buy a hybrid heat-pump hwh for $3k (canadian). The tank is still going to fail in the same amount of time (around 10yrs). So would I rather spend $400 every 10 years vs $3000 every 10 years? Since we're on PV+Batteries most of the time, it doesn't cost that much for resistance heat. Plus, the added complexity of a heat pump potentially contributing to the failure modes. Though there is something to be said about pushing all those electrons into EV charging instead of heating hot water.

2) Where we live, it does get down to -40C in the winter occasionally, but usually no lower than -25C. A heat pump hwh will take warm air from the house and turn it into hot water, putting cold air into the house causing my natural gas furnace to run more. So for half the year, my heat-pump water heater is actually just a natural gas water heater. I can install a natural gas hot water heater for about $500 vs. $3000 for a heat-pump natural gas hot water heater.

3) I know that I can try to build all sorts of ducting mechanisms for a heat-pump hwh to take warmish air from my HRV exhaust and dump its cold air outside, but I'm told that any add-on ducting to a heat pump hwh will reduce its efficiency; and of course, I only want that around half the year so I'll need dampers blah blah blah.

4) evacuated solar tubes is tempting but more complexity than I'm in the mood for.

5) I've looked into a central heat-pump that can also heat hot water but it's very cost prohibitive.

Anyway, I'm usually guilty of over-analyzing stuff. That's why I keep kicking this can down the road.
 
Here in the US we can get an income tax credit of 30% on the purchase of the heat pump water heater. Plus many utilities offer a rebate too. Here are a few of my past posts.


 
So would I rather spend $400 every 10 years vs $3000 every 10 years?

I think they can last much longer than 10 years. I took out the resistance w/h from 1992 in December 2024, it had no leaks. I had replaced the elements around 2014.

The other electric w/h is even older, and still in service.

Also, the latest models have improved materials inside the tank wands. I forgot what.
 
I think they can last much longer than 10 years. I took out the resistance w/h from 1992 in December 2024, it had no leaks. I had replaced the elements around 2014.
10yrs has been about my average across two homes in 40 years. One home had a natural gas hwh and the other an electric resistance heater. The last electric failed while still under warranty (Giant, tank sprung a leak). That one was replaced in 2022 with a new Giant. I do regularly check the dip tubes and zincs.
 
10yrs has been about my average across two homes in 40 years. One home had a natural gas hwh and the other an electric resistance heater. The last electric failed while still under warranty (Giant, tank sprung a leak). That one was replaced in 2022 with a new Giant. I do regularly check the dip tubes and zincs.
There are geothermal heat pumps that have a desuperheater built in for heating water, a desuperheater could be added to an existing air conditioner. I picked up a used water source heat pump, thinking of using it to preheat my hot water, exit temps may only be 105 F but it would be dumping 24000 BTU of heat for around 2 kw input. A cupronickel heat exchanger may last longer than a wh tank.
 
No idea, I got into the shower after my wife and niece finished theirs, to find only cold water coming out of the pipe. Checked the app, and it showed the tank's hot water was empty. I would say 50 gallon is average, at least where I live. The previous tank installed before I bought the house (3 bed 2 bath) was a 40 gallon.
It may be a common tank size however such a tank is designed to have a permanent power supply, or at least have power available most of the time perhaps only avoiding peak electricity demand period, allowing the thermostat to control when reheating occurs.

It may have a second upper heating element with an upper thermostat on a permanent power supply being used to extend capacity and provide a quick reheat to the top portion of the tank so the wait for some hot water is significantly reduced.

If you want to operate a stored hot water supply on energy supplied for only shorter part(s) of a 24 hour cycle (e.g. from solar PV and/or from off-peak electricity), then it requires a larger tank. Heat when energy is cheap to be consumed throughout the day and night. Lather, rinse, repeat. There's really no downside to having a larger tank - you consume the same amount of hot water but you'll be less likely to run out at inconvenient times.

Increasing hot water delivery capacity without changing tank can be achieved by increasing the thermostat set point temperature. You don't shower in hotter water, you just end up using a bit less hot water and a bit more cold water to get the desired water temperature.

As a rough rule of thumb, each °F the set point temperature is raised increases the hot water supply capacity by 1%. So to gain 10% more hot water delivery capacity, lift the set point temperature by 10°F. Tanks should be able to safely heat/store water up to ~155°F or more but check the specifications.

Another solution is to reduce demand - low flow shower heads.

Another might be a washing machine which heats its own water and use that only when energy is cheap. That reduces demand on the limited hot water supply. Obviously uses the same amount of hot water overall but saves the tank for personal use. Same with washing dishes, good dishwashers heat their own water and are water efficient.

Not saying make changes immediately (other than low flow shower heads) but as/when the opportunity arises.

I actually have mine set to 122 (I just like that number) for the winter, and 125 for summer.
You mentioned you set yours to 122°/125° depending on season - is that the water heater's thermostat setting (the temperature inside the tank water is heated to), or a thermostatic mixing valve setting (the temperature from the hot water outlet which is mixed with some cold water)?

If the water heater's thermostat (water inside the tank) is set to 122-125° then setting the thermostat to 150° will add 25% or more to the hot water delivery capacity (another 13 gallons or so). It will consume a little bit more energy as daily heat losses will go up but you are less likely to run out of hot water.

My daughter is 4 now, soon it will be a 3-female household.
With young children (or the elderly/disabled), if you don't already have a thermostatic mixing valve then you should (at least for the bathroom hot water supply), especially if you choose to lift the thermostat set point inside the tank. That way the actual max temp of delivered hot water will not result in an immediate and permanent burn/scalding injury.
 
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...with propane and an on-demand hot water heater :)
Local coop just called this morning, I had some propane left over that was prepaid last fall. I paid $1.35/gal last fall. Cash price is $1.60/gal. They think summer fill will be at least $1.60/gal or higher.

It takes about 250 to 300 gallons per year to run a propane hot water heater, doesn't really matter if on demand or not unless there are long periods of no usage. I own both a powervent in the house and an on demand in the shop. An on demand is not as efficient at capturing heat energy as a powervent. At 250 gallon, that is $400/year, at 300 gallon it is $480/year.

I paid $1400 for the heat pump water heater. I get a 30% tax credit so it drops the price to $980. The electricity to run it comes from my solar system. How long does it take to get my $980 back?

I do run the propane water heater in mid winter if there isn't enough PV, but it is less than 3 weeks per year.
 
Local coop just called this morning, I had some propane left over that was prepaid last fall. I paid $1.35/gal last fall. Cash price is $1.60/gal. They think summer fill will be at least $1.60/gal or higher.

It takes about 250 to 300 gallons per year to run a propane hot water heater, doesn't really matter if on demand or not unless there are long periods of no usage. I own both a powervent in the house and an on demand in the shop. An on demand is not as efficient at capturing heat energy as a powervent. At 250 gallon, that is $400/year, at 300 gallon it is $480/year.

I paid $1400 for the heat pump water heater. I get a 30% tax credit so it drops the price to $980. The electricity to run it comes from my solar system. How long does it take to get my $980 back?

I do run the propane water heater in mid winter if there isn't enough PV, but it is less than 3 weeks per year.
I like the idea of a heat pump water heater, but they lack capacity, recovery and from all the reviews I have seen, are built like shit. I would need 2-3 of them just to handle daily hot water usage (3 girls, Long showers and high flow fixtures). That said, I have toyed with an idea to use excess solar to preheat the water going into my on demand heater in the summer months.

P.S. where the hell are you getting propane that cheap? It is $2.99 a gallon around here..
 
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The issue is, on top of the heat pump water heater, you have the heat pump, and it sits in the condensate pan. So this electric thingy lives in a swamp, with 100% humidity, all the time.

Therefore, splits tend to last longer...
 

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