Electric water heater consumption

[robbob2112]

Shrug, when my 19 year old 50g tall started leaking around where the threads used to be at the top of the tank I had it replaced with a tankless gas model. For filling the jacuzzi there is no better way, other than that I think the savings are negligable. But, never ever, ever running out of hot water is priceless.

 

[wattmatters]

Shrug, when my 19 year old 50g tall started leaking around where the threads used to be at the top of the tank I had it replaced with a tankless gas model. For filling the jacuzzi there is no better way, other than that I think the savings are negligable. But, never ever, ever running out of hot water is priceless.

Heating water with gas here is more expensive.

For us using an instant gas water heater it would cost us ~A$615/year while using our excess PV costs us A$219/year in foregone feed-in credit. As our feed-in tariff falls, so does the cost of using our excess PV. Our FIT is higher than most but will be dropping before long. At typical feed-in tariffs our water heating will end up costing a little over A$100/year (~US$66/year).

Here the gas supply is becoming an issue and prices are only going one way, up. So it's important for homes to transition away from gas as the opportunity arises (e.g. when their existing system fails). I feel for those in our southern states as the gas supply crunch is coming and it's going to get expensive.

 

[robbob2112]

I hear ya, my wife is from Adelaide and has family there. When we move from Colorado to New Mexico I plan to get a place big enough to do a nice sized ground mount solar system with battery bank and with a solar heater. I want to be as independant as posssible.

 

[efficientPV]

If I override the timer in the evening I can hear the tank elements running, so, I know we are saving some usage.

How do you know that, any real data like a temperature and electric usage minute by minute? What you see can likely be done without a timer. The timer turns off the entire heater. When it comes back on only the top section is heated. By the time it switches to the lower element, the timer is close to turning off. What you likely have is a stratified hearer with the lower section at a much lower temperature. The lower section has little heat loss as it is only a pre heater. This can be accomplished with only turning the lower thermostat to its lowest setting.

 

[Bop]

Our old place, the HWS used about 3-5kwh- a year... maybe (often 0kwh)
Solar HWS, the only running cost was when we had to run it off the mains (which was maybe once or twice a year- only if it was cloudy AND we had extra guests staying in the holidays) otherwise it simply ran off the solar thermal panel...
Even it's little 12v pump was solar (a tiny little PV panel) that did the circulating during the day from the ground tank up to the roof panel thats it on the right, with the east PV array on the left (west facing array out of sight on the other side of the roof...)

For a 'ongrid house' we pretty much paid zero- the usual electric bill was around $0 a quarter- sometimes we got $20-$30 back from them even lol
One of the last bills before I moved out here... (and that was in winter lol- the PV array was WAAY down in output (but we had a bad year- multiple flooding in the area over 3 months- luckily not anywhere as bad as back in 2010- we were literally an island at that time, completely surrounded by water...)

 

[Q-Dog]

How do you know that, any real data like a temperature and electric usage minute by minute? What you see can likely be done without a timer. The timer turns off the entire heater. When it comes back on only the top section is heated. By the time it switches to the lower element, the timer is close to turning off. What you likely have is a stratified hearer with the lower section at a much lower temperature. The lower section has little heat loss as it is only a pre heater. This can be accomplished with only turning the lower thermostat to its lowest setting.

I can see our usage go up on our smart meter app when I run the water heater. Our water heater has a 1 hour recovery and we run the timer for 3 hours every morning to make sure we recover after morning use. We just let it coast the rest of the day unless we have heavy use.

 

[wattmatters]

One of the last bills before I moved out here

Memories of back when AGL had a 20c FIT offer. That's long gone now. I couldn't justify it at the time in my area as the overall bill was higher than plans with lower FITs.

Yeah if you have a home here with an existing working solar thermal water heater then it's a good thing. But once it reaches end of life they are no longer economic to replace with new ones.

multiple flooding in the area over 3 months- luckily not anywhere as bad as back in 2010

Where are you now Bop? I'm guessing you were in SE QLD given the 2010 flood reference. That was a bad one.

 

[robbob2112]

I can see our usage go up on our smart meter app when I run the water heater. Our water heater has a 1 hour recovery and we run the timer for 3 hours every morning to make sure we recover after morning use. We just let it coast the rest of the day unless we have heavy use.

So the question is - If you just left it the water heater on verse having it recover in the afternoon would it matter?

I.e. measure usage for it for 24hrs from the water heater and measure 24hrs with the timer and see if there is a delta?

 

[Bop]

Memories of back when AGL had a 20c FIT offer. That's long gone now. I couldn't justify it at the time in my area as the overall bill was higher than plans with lower FITs.

Yeah if you have a home here with an existing working solar thermal water heater then it's a good thing. But once it reaches end of life they are no longer economic to replace with new ones.


Where are you now Bop? I'm guessing you were in SE QLD given the 2010 flood reference. That was a bad one.

Yeah was in brisbakers back then- not a good time... moved when I bought my new place (bit further inland lol) 40 acres of bushland...

That's from the road out the front, my place is 1/2 km back where the arrow is, back fence is a kilometre further back lol

I'm currently using a 'home brew' thermal solar HWS (50m of polypipe laying on the ground lol, with an old 400l tank inside the shed- because it is higher than the coil of polypipe it naturally thermo-siphons without a pump, and actually works quite well, but once the house is done and the full PV array is up on its roof, then it will be used to run the electric elements of the tank... (so still solar HWS, but PV driven rather than thermal panels)

 

[wattmatters]

40 acres of bushland

Ah, I'd already asked this in another thread, I just didn't make the connection.

I'm currently using a 'home brew' thermal solar HWS

Neat. It's amazing how much heat can be collected by pipe/hose.

 

[Bop]

Ah, I'd already asked this in another thread, I just didn't make the connection.


Neat. It's amazing how much heat can be collected by pipe/hose.

Indeed, that coiled up 50m of polypipe gets the hot water to an uncomfortably high degree (luckily as this isn't a pressurised system, it just vents water back to the rainwater water tank back through the pump, rather than building pressure in the tank- as it is, even in winter in cloudy weather it still gets quite hot, and with the heatwave we have been having, the water coming out of the hot water tank gets to practically boiling point.... (I literally can make coffee straight from the tap lol)

 

[CaliSunHarvester]

You can get 8 channels of monitoring for $100-150 with an Emporia.

It's been a while but I wanted to follow up here.
The lowest daily consumption was 19kWh and the highest was 25kWh by the 80G resistance water heater.

Several comments about adding insulation. This unit is inside the house, in a not very cold basement type room. The tank does not feel warm to the touch. I don't think insulation helps.

I noticed one shower head disburses like 3x as much water as another shower (which is much less enjoyable to me, but at least it has the nicest tile job).

I had not expected consumption above 20kWh.

That's $12+ a day. If a heat pump wh can cut that in half, it would save $2000+ a year. The cost of the new unit including condensate pump.

A no brainer.

 

[wattmatters]

It's been a while but I wanted to follow up here.
The lowest daily consumption was 19kWh and the highest was 25kWh by the 80G resistance water heater.

Suggests to me you are consuming almost a full tank every day. In that case heat pumps are definitely worth looking in to, as are consumption reduction measures. Take a bit of time to research heat pump water heaters as quality varies quite a bit.

I had not expected consumption above 20kWh.

That's $12+ a day.

Is your tariff for heating water really 60c/kWh?

 

[wattmatters]

For us using an instant gas water heater it would cost us ~A$615/year while using our excess PV costs us A$219/year in foregone feed-in credit. As our feed-in tariff falls, so does the cost of using our excess PV. Our FIT is higher than most but will be dropping before long. At typical feed-in tariffs our water heating will end up costing a little over A$100/year (~US$66/year).

Circling back on this earlier comment I made.

Our retail electricity plan has just changed and our feed-in tariff (FIT) has reduced which means our water heating cost will now be less than A$130/year. Benefits of self-consumption of our solar PV means the FIT is less important.

Our FITs will continue to decline in the years ahead, especially during the middle of the day as distributors begin to charge retailers (a little bit) for customers exporting power. Negative daytime wholesale prices are also putting downward pressure FITs. But it's also putting downward pressure on daytime power prices.

The plan I am about to start has a 2-hour free energy window during 12-2PM on weekends. So on weekends I can charge up the water heater, battery, EV etc.

 

[CaliSunHarvester]

Suggests to me you are consuming almost a full tank every day. In that case heat pumps are definitely worth looking in to, as are consumption reduction measures. Take a bit of time to research heat pump water heaters as quality varies quite a bit.


Is your tariff for heating water really 60c/kWh?

Google search "PG&E rates"



This is a bill from last year's July when solar was really making a dent. Look at the baseline allowance of 213kWh.

Prices increased 13% on 1/1/2024 since then.
Working hard to move things to off-peak.
January 2023 we used 1982 kWh in a single month.

 

[CaliSunHarvester]

53c + 13% = 59.89c

Keep in mind that there are some fees and taxes on top of this, some are flat fee and some a function of consumption, I believe.

And PG&E applied for another increase effective 7/1/2024, IIRC.

 

[wattmatters]

Google search "PG&E rates"

Sure, but do you not heat water when the rates are cheapest?

That's the whole point of a hot water storage system. Heat the water when energy is cheapest (be it via off-peak grid power or from your own solar PV) to then be consumed throughout the day. Obviously you need a tank of sufficient size to store day's worth of supply (and preferably a bit more than that).

This is normal here - millions of electric water heaters are on dedicated off-peak supply. Many are also now moving that to daytime running to consume their own solar PV.

 

[wattmatters]

Even so, the heat pump route seems sensible given the high consumption. If the climate is mild then good ones will use 1/4 of the energy of an electric resistive element. High quality ones will not need a resistive element for "boost", they are designed to work well when ambient temps are low.

Combine a heat pump water heater timed to run from off-peak and/or solar PV and water heating operating costs will plummet. Decent heat pump water heaters will have programmable controllers to set times of day they operate.

 

[CaliSunHarvester]

Sure, but do you not heat water when the rates are cheapest?

That's a good theory. It works for running the dryer. The water heater, even though it's 80G, comes on when people use hot water. Not instantly, but definitely any time someone showers, it comes on, minimum 15 minutes, and as long as a bit over an hour. Peak is 4pm to 9pm, definitely water use during that time.

And off peak is not much cheaper. 50c vs 60c.

"Free electricity window" on weekends. Amazing. You cannot be in California.

 

[CaliSunHarvester]

the heat pump route seems sensible given the high consumption. If the climate is mild then good ones will use 1/4 of the energy of an electric resistive element

1/4. Wow. Should have done it last time when I cleaned out the tank.
Better now than next year.

My buddy is coming over right now. He wants to buy a new truck. We will check out where to run the drain line today and swap the wh next week.