Electric water heater consumption

[CaliSunHarvester]

With some circuits now powered by solar, I thought we would not consume as many Wh. Last night, over a 13h interval, the meter moved forward by 36 kWh. We do have 3 electric water heaters on the property.. one is 19G @ 120V (outside, vacant house), one is tankless and nobody was there last night and the 3rd one is 80G @ 240V, with each (??) heating element being 4500W.

1) I think it's actually 4500W combined across them, since I only have 10AWG wire feeding them. Is this right? It cannot be 4500W per element.. that would be 37.5A per leg.

2) assuming the WH runs 4h a day, that would be 4 * 4.5 = 18kWh a day. This kind of fits the consumption.
What's the best way to measure the consumption over a period of time? Should buy a watt-meter? Like this for $100:

https://www.ekmmetering.com/products/universal-single-phase-kwh-meter

I rather not spend $100 to confirm that my water heater is the big consumer. It's an old unit.. 30 years old maybe.

3) what are my options to save electricity? With the 10AWG wiring, I cannot install a tankless electric WH. The location does not allow a gas heater - it's deep inside a basement, 40+ feet away from an exterior wall (cannot vent).
I looked at "hybrid water heaters". They extract heat from the surrounding room. Not sure how that would work in the basement location. Any suggestions? Going from 80G to 50G alone should save some energy, right? I don't know why they put that big unit in.. it won't fit through the door, I will need to cut it up to remove it. Wall was built after WH install LOL The house has 3 baths and 2 kitchens.. a recirc pump is sitting next to the WH; looks like from the 80s as well, was never installed.

Any other ideas? More panels to cover the greedy WH?

 

[yodamota]

what about putting them on timers? do you need hot water overnight? How would the vacant one be cycling? unless is turned on when you are not using it?

 

[CaliSunHarvester]

The vacant one is an issue. It is kind of outside protected only by lattice. So, yeah, that one gotta be cycling. This is in coastal California, the WH spot gets probably to 40-45F in December - January.

That house is not really vacant. The tenant is there about 6 nights a month.


Timer for the 80G unit.. we do shower in the evening, then nothing until 6am. The timer would need to be for 240V 30A.. like for a pool pump. I think I actually have one somewhere.
But does that really save energy? Wouldn't the WH then work full force at 6am?

 

[BKY2003]

I have a 80 gallon tank. I put in two 240v 2000 watt elements. It has a timer set for 30 minutes at 4 o’clock and at 11am for 1hour and a half. Seems to work for us. But I am in Florida so my well water is a little warmer.

 

[CaliSunHarvester]

what a brilliant idea, just put in smaller elements!! If it doesn't work, I can just go back to 4500.

See, I don't really like to spend $2000 on a hybrid wh and after a few months I know it was not worth it.

At least not until the old one broke.

 

[zanydroid]

I rather not spend $100 to confirm that my water heater is the big consumer. It's an old unit.. 30 years old maybe.

You can get 8 channels of monitoring for $100-150 with an Emporia. Much easier than what you linked, and IMO folks that fancy themselves home electrifiers/solar people should reach for energy monitor by default.

They extract heat from the surrounding room. Not sure how that would work in the basement location.

The manufacturer only specs ambient temperature and enough airspace. They're only pulling 4500 BTU/h, they're not monster units.

They do need a drain location for condensate.

 

[BKY2003]

Only reason I changed my elements to 2000 watts is because my hot water heater is totally off grid. (Solar, and battery) when I had the 4500 watt elements in I just had the time on a shorter schedule. So you don’t have to change the elements.

 

[CaliSunHarvester]

They do need a drain location for condensate.

Good to know. You probably guessed it, I have no floor drains down there. Nor pumps.

Thank you, also for the Emporia tip. I will buy that.

 

[zanydroid]

Good to know. You probably guessed it, I have no floor drains down there. Nor pumps.

Yeah if the water heater is like in the middle of the room you'll probably need a lift pump and then a long new PVC. IMO that's the disqualifier more than room shape, a lot of the time, because you can cut vents or swap to louvre doors to get the air volume. But water drainage is not so easy.

Thank you, also for the Emporia tip. I will buy that.

Cool. Super easy to install. BTW it has 16 total channels if you need that many. I think their app also merges from multiple (if you have multiple subpanels). I actually do use 16 channels on my 1800 sqft house :laugh:

 

[time2roll]

Amazon condensate pump $50

These are used all the time with air conditioners.

 

[zanydroid]

Amazon condensate pump $50

These are used all the time with air conditioners.

Oh sure, it's not rocket science. Less elegant than gravity drain, and need to do some additional testing of what happens if it fails.

 

[yodamota]

The vacant one is an issue. It is kind of outside protected only by lattice. So, yeah, that one gotta be cycling. This is in coastal California, the WH spot gets probably to 40-45F in December - January.

That house is not really vacant. The tenant is there about 6 nights a month.


Timer for the 80G unit.. we do shower in the evening, then nothing until 6am. The timer would need to be for 240V 30A.. like for a pool pump. I think I actually have one somewhere.
But does that really save energy? Wouldn't the WH then work full force at 6am?

I suspect most of the time you are putting cold water on at the same time when using the hot water in the shower? So maybe set the timer to come on at 5am and shut off after the showers. experiment from there.

I guess we sip by on water that isn;t hot at all in the winter months. sometimes just the hot water being on full blast is a pleasant shower. no cold required.

could you reduce the temperature on the water heater? most are set to 140*F

 

[fromport]

See, I don't really like to spend $2000 on a hybrid wh and after a few months I know it was not worth it.

As a reference:
2 person & some animals 1700 sq ft home in southern california, using a 40 gallon hybrid water heater, we used 930 kWh of electricity over 2023 for our warm water.

 

[CaliSunHarvester]

Yeah if the water heater is like in the middle of the room you'll probably need a lift pump and then a long new PVC. IMO that's the disqualifier more than room shape, a lot of the time, because you can cut vents or swap to louvre doors to get the air volume. But water drainage is not so easy.

Cool. Super easy to install. BTW it has 16 total channels if you need that many. I think their app also merges from multiple (if you have multiple subpanels). I actually do use 16 channels on my 1800 sqft house :laugh:

We have 9 panels.. 7 of them on grid.
Probably ~90 circuits. Ordered the 16 channel package on Amazon.

 

[CaliSunHarvester]

used 930 kWh of electricity over 2023 for our warm water.

My conclusion for now is that I need exact consumption numbers. 930 sounds great. I think we are around 6 times that number. I cleaned out the wh last year (sediments).

 

[SupraSPL]

The top element turns on first and when it reaches temperature the bottom element kicks on, so it only draws 4500 Watts at a time. If you switch the water heater to 120 volts instead of 240 it'll work the same except each element will only draw 1100W at a time. All you have to do is move one leg to the neutral bar.

That makes the hot water heater more inverter, watt meter and timer friendly (I use the 120V 15A wyze power plug to control mine) but in order to actually save power you would have to address the standby losses which are about 70 watts, 24/7 or 1.7 kwh per day. You can reduce that a little bit by turning it off when not in use, reducing the temp and insulating the water heater and water heating pipes.

I measured the total power consumption during a warm, very low pressure shower and it used power at a rate of 6,500 Watts. So in theory you could take a decent shower with a 6500W instant water heater but also it helps to keep in mind that as long as that shower is turned on you're consuming energy at a rate of 6,500 Watts or more. If you have really good sun that's a good day for a longer shower but if there's really bad sun, it's motivation to take a short one or skip a shower.

The most energy efficient way to get clean, that's not uncomfortable is a dark colored cloth and a 250 watt heat lamp ?

 

[CaliSunHarvester]

top element turns on first and when it reaches temperature the bottom element kicks on,

Are you saying that only one of the 2 elements work at any given time? (Or none)

Makes sense that it's called 4500W then...

 

[zanydroid]

My conclusion for now is that I need exact consumption numbers. 930 sounds great. I think we are around 6 times that number. I cleaned out the wh last year (sediments).

It should be 3-3.5x more efficient with a HPWH over a WH, as long as the ambient temperature is in the range where the HP can work (which it should be to avoid freezing your pipes).

The EnergyStar UEF numbers are between 3-4 depending on tank size.

We have 9 panels.. 7 of them on grid.
Probably ~90 circuits. Ordered the 16 channel package on Amazon.

9 Subpanels? And I thought I was extra to have 3.

The top element turns on first and when it reaches temperature the bottom element kicks on, so it only draws 4500 Watts at a time. If you switch the water heater to 120 volts instead of 240 it'll work the same except each element will only draw 1100W at a time. All you have to do is move one leg to the neutral bar.

I wonder if pulling 120/240 to give you 25% and 100% by adding a SPDT contactor at the heater to swap second wire between N and L (no clue if this is to code) would be a good idea.

 

[CaliSunHarvester]

9 Subpanels?

10 panels. 1 main panel, 7 cascaded sub panels, some have just 6 or 8 breakers. 2 off grid panels.

It's a farm type property with too many buildings.

 

[Daddy Tanuki]

10 panels. 1 main panel, 7 cascaded sub panels, some have just 6 or 8 breakers. 2 off grid panels.

It's a farm type property with too many buildings.

sounds like a good reason to make the outbuildings stand alone with their own panels etc. and use the mains coming into the main building to run chargers when needed for the outlying ones.