Electric water heater consumption

[wattmatters]

So 200G for all of us.. 50G per person.

Yeah that's pretty good.

Ours has fluctuated a lot over the years but normal usage is ~ 300-350 litres/day (~80-90 gallons) for the two of us. Except when establishing gardens and when I had an undetected leak which was too slow to notice and gradually increased over the years until I couldn't work out why the water bills was so high. We are on town water supply which is river fed.



Two dwellings now / 4 people.

We have a pool and gardens that get a drink during drier periods if needed. Only one rainwater tank but it's in the wrong spot for us to use on our home's gardens. Would like another tank but the cost is silly compared with town water supply. I have a lot of rooftop collection area though.

 

[DIYrich]

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.

Heat when rates are cheapest. If you need more hot water:
1) Heat to 145 degrees. Add a thermostatic mixing valve to blend with cold water to 120 degrees
2) Larger tank

 

[Bop]

Heat when rates are cheapest. If you need more hot water:
1) Heat to 145 degrees. Add a thermostatic mixing valve to blend with cold water to 120 degrees
2) Larger tank

LOL- Welcome to the 1970's guys...
(just watched that video- thats how off-peak HWS systems have worked for decades in Australia)

(never seen any with pipes running out the top though- is that a common thing in the US???)
That's a typical Aussie HWS (250l for 1 to 2 people, 300l to 400l for a family with twin elements) tempering valve on the side (orange knob) with the HWS usually running about 70C, but running on off-peak (turned on by signals sent through the mains power itself- if you have ceiling fans running at night, you could often hear the signals as a slight change in the motor hum)

Typical older (1960's-1970's) Australian single phase fuse box complete with the old ceramic fuses (houses with 3 phase had 3 meters with no offpeak, 4 meters with off peak)- the meter on the left is the 'main' power meter electricity 24/7, the meter on the right is the 'offpeak' meter and is switched on and off by the signalling switch bottom right through 'tones' sent through the mains wiring, different 'tones' switch different groups of houses on and off at different times to spread the night load more evenly
If you didn't have offpeak (or had it removed when fitting solar- it used to cost about $40 a year extra on the bill years ago before when the last time I had a non solar HWS)- so going solar you automatically had it cut off to save money lol) you only had a single meter, and the boost element ran at full rates

This is the fusebox where I used to live- before and after the solar was installed, back in 2016

You can see in the 'old' photo where the old off peak meter used to be (removed around 2000 when the solar thermal HWS was fitted)- the offpeak switch position was replaced by the 'earth leakage' breaker bottom right (its actually an RCD, but Aussies still call it 'earth leakage', same as its still called a fusebox, even though we have used MCB's instead of fuses since the late 70's or so lol (lol- you can see in both photos the electric boost for the solar HWS is turned off- the orange MCB- orange for HWS, green for solar is 'suggested' but not legally required)

We are required by law to run the HWS itself at a minimum 60C (kills legionnaires disease etc), but the tempering valve keeps the hot water coming from the taps at no more than 50C

This explains how tone switching (ripple control) works, and why it is becoming an issue- with many suppliers looking to phase it out entirely over the next 6 years entirely (especially since the major use was switching offpeak HWS systems on and off, and most homes having had solar HWS for several decades- it really isn't needed any more, plus smart meters can do it now, so its use is even less needed...
LED-Lights-and-ripple-control-frequencies

 

[wattmatters]

(never seen any with pipes running out the top though- is that a common thing in the US???)

Yes, it's more common for tank design in America for the cold water entry through the top. The cold water pipe extends all the way to the bottom of the tank. I'm not sure why that's more common over there, other than perhaps it suits basement installations better given the water pipes are probably coming from overhead. As you know, basements are uncommon in Australia. Our tanks are often outside, or in the laundry.

Typical older (1960's-1970's) Australian single phase fuse box complete with the old ceramic fuses (houses with 3 phase had 3 meters with no offpeak, 4 meters with off peak)

Exactly what our current early '70s build home had - three phase, four meters, ripple controller for the controlled load water heater. I wish I had taken a photo of it before I had the board upgraded not long after moving in.

When we installed solar PV two new smart meters replaced the four old spinning disk analogue units, one polyphase meter for general supply/solar and a second single phase meter for the controlled load.

With the modern meters I can download my detailed interval data the next day (if the retailer has that facility on their customer portal) else I can request the meter interval data from the distributor.

If you didn't have offpeak (or had it removed when fitting solar- it used to cost about $40 a year extra on the bill years ago before when the last time I had a non solar HWS)- so going solar you automatically had it cut off to save money lol) you only had a single meter, and the boost element ran at full rates

Yep, ours adds about 11c/day to the cost, although it can get a bit variable depending on the distribution zone (each have different charge rates for CL metering) and the retailer who bundles it all together masking their input costs. I've just changed to a Red Energy plan and they don't appear to be charging me any extra for it. This is our ripple controller:

I'm not using it as my water is now heated with a PV diverter, but it is still available for overnight boosting if I so choose. My diverter's default mode is to use the off-peak boost if the solar PV didn't complete a full charge. I put it in solar PV only mode so it doesn't do that as I want it to avoid grid imports as much as possible.

It also has a "heat now" button, which is going to come in handy with the two hour free power window on weekends, especially on cloudy days. Diverter:

 

[Bop]

Many old electric offpeak HWS's had no option but to wait until it heated up again overnight, but quite a few had a heavy duty 15A to 40A switch that allowed it to run from the 'main' peak meter if required- either inside the house (usually in the laundry) or in the fuse box... (just remember to turn it off again after using it to boost- or all your heating costs go to the main meter on the higher rates!!!)- some had a 'one time' press to boost feature that used a magnetic coil to hold it in until the heater element turned off in the tank,and then released it- the actual main current flow to the heater went through a coil around an armature, which when pressed in, the flow of current to the heating element set up a magnetic field and that held the contactor in the 'on position' until the tank was hot, then when the thermostat opened in the tank, the current flow stopped and so did the magnetic field, releasing the spring loaded contactor arm and the button popped out- they worked, but you knew the tank was heating- it 'buzzed' continually (not overly loud, but definitely noticeable lol) until it released due to the AC waveform- I had one in a house in Sydney

 

[CaliSunHarvester]

Here is an update. I still have the old electric water heater, but I was able to bring consumption down from 20kWh a day to 12.5kWh a day. Which still is a lot. Measures were cheap and easy:

- new aerators on sinks that reduce flow further (55% less)
- 1 new shower head
- shorter showers (myself only, could not really go further)
- I started to do the dishes which made my wife really happy. She has not complained that I put dishes still dirty in the cabinets.

However, I did move the new electric dryer which also has a heat pump, on the solar electric panel, and today I measured actual consumption. This dryer has a 30A 240V plug, so I expected some serious current. I measured with a clamp meter on both legs and the highest I saw was 1.89A.
Separately, I had this hooked up to one of the legs:




The first picture was taken 8:36am, the second after the dryer was done at 10:22am.

Apparantly it uses 0.8W when turned off, probably because it's connected to WIFI waiting for remote instructions.

The first picture shows 30.7W consumption (per leg!), but it has been as high as 180W. I think 1.89A * 120V = 227VA but due to pf = 180W

I verified several times with my clamp meter that both legs have the same current.

The display shows a consumption of 45.26-45.01 = 259W. Multiply by 2 for both legs..

about 520Wh.

I could not believe it! Opened the dryer.. and the clothes are indeed dry!

I never measured the old dryer (from 1980) but based on internet queries, it probably pulled 4000W for a full hour, or 4kWh for one load.

520Wh vs 4000Wh!!

If the water heater achieves anywhere near these savings, that would be awesome.

And here today's energy usage; I had turned off the water heater prior to starting the dryer, because I feared I would come too close to the inverter's 10kW limit:



Obviously, I should turn the water heater's breaker back on now. I look forward to a nice nearly flat graph once the heat pump water heater is installed.

 

[marionw]

Solution: Turn your underwear inside out and wear for another day. This will cut down on laundry!!!!

Let the dog lick the plates clean then put them away.

 

[wattmatters]

I could not believe it! Opened the dryer.. and the clothes are indeed dry!

I never measured the old dryer (from 1980) but based on internet queries, it probably pulled 4000W for a full hour, or 4kWh for one load.

520Wh vs 4000Wh!!

Ours uses ~1 kWh per load. Here's two loads from the other day which used 2.34 kWh. Power consumption varies but generally under 1 kW.

If the water heater achieves anywhere near these savings, that would be awesome.

For the same consumption a heat pump water heater will use a lot less energy than resistive element. 1/3rd to 1/4.

 

[CaliSunHarvester]

Solution: Turn your underwear inside out and wear for another day. This will cut down on laundry!!!!

Let the dog lick the plates clean then put them away.

Did you know that females change underwear several times a day? The ones in our household do.

The dog plan is better.. we have 3 who already do lick plates.. usually while the plates are still on the table

 

[CaliSunHarvester]

Ours uses ~1 kWh per load.

which model do you have? I will measure on further cycles, maybe today was just a "light load".

I bought this Samsung, delivered/ installed in December 2023:

Samsung 4.0 cu. ft. Smart Dial Heat Pump Dryer with Sensor Dry in White color DV25B6900HW - The Home Depot

Samsung's 4.0 cu. ft. Large Capacity Heat Pump Dryer gives you a ventless, more energy-efficient, cost-effective and gentle way to dry your clothes. It is equipped with our AI Smart Dial, which learns

www.homedepot.com

 

[DIYrich]

Turn your water heater down to 80 degrees. That will reduce the amount of heat you have to put in the water, and make your showers a lot shorter.

 

[CaliSunHarvester]

Turn your water heater down to 80 degrees

I messed with the thermostat many, many months ago already. It's not like there's a digital display showing "80". This water heater is from 1994. 30 years old now, and no issues!

The mark used to be at "A" and for the past 6 months(?) it has been as low as I can turn it:

 

[wattmatters]

which model do you have?

It's a Bosch Serie 8 heat pump tumble dryer.

 

[exmarkretired]

Solution: Turn your underwear inside out and wear for another day. This will cut down on laundry!!!!

Let the dog lick the plates clean then put them away.

Dog appreciates this too!

 

[CaliSunHarvester]

Ours uses ~1 kWh per load. Here's two loads from the other day which used 2.34 kWh. Power consumption varies but generally under 1 kW.

660Wh today, she had selected the "heavy duty" option this time.

 

[JRH]

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.


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.

Totally correct about monitoring yer power….I think I probably save about what my monitor unit cost me 2-3 times a year by being made aware of what’s running…by my blue tooth display…
I tend to forget whats on and why…

Before I got it I thought I don’t need that …
I was wrong…
Obviously I’m not smart enough to be aware of what’s on all the time..

Everytime I pick up my phone it’s telling me to go turn something off.

It’s amazing how much I don’t waste anymore …..

J.

 

[wattmatters]

660Wh today, she had selected the "heavy duty" option this time.

Sounds good. It depends on many factors, how wet the clothes are to start with, ambient conditions (especially humidity), size of load etc. And some units have higher coefficient of performance. It's fairly humid where we are so no surprise a bit more energy is needed.

Looking back we have some loads which use 700-850 Wh.

Most of my loads use zero Wh to dry as they are hung on the clothes line.