Is It Worth Removing Controlled Load Meter if You Have Solar?

Dr-StrangeLove on 20/01/2025 - 11:01

I have a seperate controlled load (CL) meter in my property which serves solely for the electric water heater. It runs only during non peak hours and consumes a lot of energy. However prices per kWH for CL is significantly less than normal rates. Since the appliance consumes so much power, end of the term the price of both meters are almost the same.

I am wondering if I can reduce my power bills by removing CL meter. I have a 6.6kW solar panels. Would that be sufficient to service water heating? Assuming it is running on full capacity in the middle of the day.

I have looked into switching to heat pump water heaters. But the noise is too much from it and also I recently replaced my old heater so don’t want to discard it now.

TIA

Home & Garden

Comments

killingtime on 20/01/2025 - 11:20

+2

Going to need some more numbers from you. What model got water cylinder? What's the usage pattern. Are you already using up all your solar now? What are the electricity prices?
wannagrababargain on 20/01/2025 - 11:24

+1

It takes about 5.25 kWh to raise 100 litres of water from 15 degrees to 60 degrees. Generously assuming 100L per day consumption of hot water. This is about 3 hours at 2 kW of excess solar output each day - in worst case scenario is this achievable in Winter? Although you have bills with actual kWh consumed of that one appliance so the maths should be pretty easy to work out. Regardless if you're feeding back a lot of solar to the grid it's generally better to try to self-consume it. The small number of days where you have to top up from the grid would likely end up costing a lot less than CL every day - assuming you have the solar generation to spare.
- Dr-StrangeLove on 20/01/2025 - 12:02
  
  That calculation sounds about right. I have AGL app and as per the data there, consumption is less than 3kWH a
  during the time at night when it runs.
Baysew on 20/01/2025 - 11:34

It runs only during non peak hours

In situations where you run out of hot water during the day and need to heat water during the day, there may be a boost switch.
BOGOF on 20/01/2025 - 11:59

+1

I installed solar a couple of years ago and removed the CL meter at the same time.
Got the sparky to install a timer on the H/W circuit to only heat during times when solar panels could possibly generate.
Currently I have the water heater on a timer from 8:00 - 16:00. Never run out of hotwater.
- Dr-StrangeLove on 20/01/2025 - 12:01
  
  Thanks, did it help reduce bill?
  - BOGOF on 20/01/2025 - 12:03
    
    Massively.
- AB100 on 20/01/2025 - 12:23
  
  +1
  
  I did the same, but I also replaced the 3600w heating element in the H/W with a 1800w one. Takes longer to heat the water, but didn't overwhelm my solar system.
  - Lichen6420 on 20/01/2025 - 13:57
    
    This is actually more relevant. As above most largish electric hot water systems have a 3.6kw (3600w) heating element.
    
    Having only a small 6.6kw solar system this does not leave much left over for other loads, particularly in shoulder production times and winter months.
    
    Get a timer installed and a smaller element put in the HWS at the same time.
JIMB0 on 20/01/2025 - 12:12

+1

A solar diverter would dump any excess power into the hot water heater. A cheaper option would be using a lower power element and a timer.
Shame on 20/01/2025 - 13:29

+1

Depends what your controlled load tariff is. If you use 3kWh a day at 22 cents per kWh that is 66 cents per day or $240 per year. An electrician to remove the controlled load would cost $400 (guess?) so it would take 1 year 8 months for payback.

I'd probably just wait until I need an electrician for another job and have them do it then or else just wait until the hot water tank dies.

Do your own calculation
cashless on 20/01/2025 - 15:59

I have solar panels but my hot water on CL like you OP.
Difference for me is that the solar runs two pool pumps (one for filtration, one for a separate solar heating roof array), meaning that I don't generate a lot of excess power to heat hot water.
Like you I've looked at heat pumps, but decided that coming off the CL and installing a heat pump was a lot of fussing and expense.
I looked at running a heat pump on the CL, but that isn't an efficient option either.
In the end my mind was made up when the old hot water tank blew up and I have to get a replacement in fast.
What really p1sses me off is the way the energy providers have started to creep up the cost of the CL tariff, because the CL is really my only electrical expense.
Have checked out all the providers in my area and they all seem to have increased the CL tariff over the last couple of years.
Options are to fit more solar panels or move off the CL and use heat pump.
But yeah, getting the decision right is tricky because you have to weigh up so many factors.
And just when you think you've got things right the energy provider whacks you again.
Euphemistic on 24/01/2025 - 06:36

I looked at a solar diverter for hot water. At the time it was not economical to do so.

One thing i considered is that we use most hot water at night, therefore the solar would not do a lot of heating and the CL would be used to heat water overnight. If there was not enough sun the following day and the CL didnt heat the water we would possibly not have enough solar to give us hot showers in the evening.
- lgacb08 on 24/01/2025 - 13:01
  
  That's a bit of a simplicitic assumption on those devices, these diverters do have the option to set minimum runtime and manual override to make sure the tank got heated every day. Otherwise a simple time based controller will get you out of trouble most of the time, unless you're in vic and only have 6kw system because you will import a fair chunk in winter.
  - Euphemistic on 24/01/2025 - 14:58
    
    It probably is a bit simplistic, but essentially, to get either free solar heating or use cheapest off peak rates to heat water, then it either heats in the day or overnight. If you use the bulk of your hot water in the evening then its not ideal if the sun dont shine. If you cant heat on solar, you'll want to be finishing the heating in evening (peak) rates to ensure hot showers for all.
    
    It significanlty changes the equation if you predominantly shower in mornings. If the solar doesnt heat your water in the day, you can use off peak overnight and be guaranteed cheapest hot water.
    
    What we probably should see in the current market is a shift to controlled load activating when there is excess renewables in the grid, rather than overnight. Overnight (10pm-7am) was initially used to ensure there was load for coal stations so they didnt need to ramp down so much at night.
    - lgacb08 on 24/01/2025 - 22:33
      
      Electric storage only heat once a day only so it doesn't matter what time it start and stop. You should not undersize your electric storage system to begin with, and insulation means it doesn't matter if you shower in the evening or morning. moving controlled load to peak solar hour already happens and it doesn't support your argument of running out of water in the evening either because of reason above. Of course those designing solar diverter capable of doing last minute heating already account for peak power start time and and allow for such event. For 3.6kw element an hour or two runtime will be more than enough, statistically speaking that only cost $4 at most for a relatively large tank. Converted that amount to controlled load cost is like 2 or 3 days at most. Statistically speaking there is no such place in Australia that you can have the odd of having 1/3 of the month to be extremely overcast.
      - Euphemistic on 24/01/2025 - 23:14
        
        @lgacb08:
        
        Electric storage only heat once a day only so it doesn't matter what time it start and stop.
        
        If you have solar diverted to hot water and controlled load overnight, it will heat whenever the temp drops below the set point and use power whenevr available. It then stops heating at the high set point. Water heaters are dumb the heat when power is avaiable and the water is not hot enough.
        
        If you draw hot water at night, itll heat overnight first, the not require solar because its already hot. If your solar heats it during the day, after modning usage and gou dont use innthe evening, the CL wont
        kick in
        
        Anyway, when i did the sums a long time ago, it wasnt worth it. Power prices have risen since, and feed in is poor now, so maybe its more econimcally viable.
        
        lgacb08 on 25/01/2025 - 21:31
        
        @Euphemistic: Doesn't work that way mate, if you're on solar diverter, you'll be taken off controlled load, no installer would be silly to leave the tank on controlled load because that doesn't make sense (and physically impossible).
        Back in the day controlled load used to be dirt cheap but not anymore, similar to LPG vs petrol. If you're in anywhere other than Vic or TAS then switching off controlled load can easily pay for itself within a few year, in vic with government rebates and poor solar output in winter heat pump is the better option.
        
        Euphemistic on 26/01/2025 - 06:48
        
        @lgacb08: All the solar diverter does is push power to the hot water when its available. The HWS will still need an additional power supply. In my investigations, admittedly some time ago, the HWS also stayed on controlled load.
        
        lgacb08 on 27/01/2025 - 22:46
        
        @Euphemistic: no, solar diverter is the power supply, it runs on main circuit when there's always power. Controlled load is on its own circuit and there's no power into it most time of the day. Unless your hot water is specially designed and have 2 set of wiring running into it, it can only accept either of the above. Solar diverter has its own mechanism to measure how much excess pv energy generated and only allow the heating element to take up the excess energy instead of drawing constant amount from the grid.
        
        Euphemistic on 28/01/2025 - 09:03
        
        @lgacb08: What youve just described leads me to think you have very little idea about how electrics work.
        
        A solar power HWS will have a backup off the grid. Thats not '2 set of wiring'. It will have a contactor or switch at the switchboard.
        
        lgacb08 on 28/01/2025 - 12:33
        
        @Euphemistic: Contrary to your belief I have my hot water tank installed with diverter and qualified to speak after the fact. And it was done on the solar hot water tank with roof top collector too. You need to get your fact straight and stop making judgement based on incorrect assumption. Have you seen the wiring behind the meter with ripple relay for controlled load yet?
        
        Euphemistic on 28/01/2025 - 14:38
        
        @lgacb08: So its not a controlled load HWS you have installed. Its a solar HWS that had a controlled load booster. That is different to an off peak HWS.
        
        Im now wondering the benefits of adding solar boost to a solar HWS. Surely when the HWS isnt getting enough sun to heat the water, there is also limited solar power input.
        
        lgacb08 on 28/01/2025 - 15:26
        
        @Euphemistic: Yes it is a controlled load hot water system regardless because without solar or even the reticulation pump running it will have to rely on off-peak tariff to heat up. No wise man would want it connected to normal tariff for backups purposes because the rate will be astronomical. The only thing connected to main circuit is the reticulation pump with its controller board but it is there to circulate the water.
        Your second statement doesn't understand the principle of a proper diverter, the heating element always draw a fixed amount of power (e.g. 3600w) under normal circumstances. For a 6.6kw system that doesn't leave much room for error on a cloudy day and will cause grid import charges. A diverter can vary that amount to make sure you never exceed your solar output, so if you only have 2000w spare it will draw that much. As long as the tank consume 5 or 15 kwh for the day there will be enough hot water. That's what makes the difference.
        
        Euphemistic on 28/01/2025 - 16:09
        
        @lgacb08: Seems we are talking about two separate steups. No wonder theres been confusion.
        
        You have a solar HWS that has a collector on roof, tank on ground and a reticulation pump? And its connected to controlled load too? And has mains for the pump and a solar diverter? Theres something youre not describing well, not to mention shifting the goalposts along this thread.
        
        OP has a straight off peak HWS. No solar, no retic pump. In that case the solar diverter would 'divert' otherwise excess solar to heat the HWS instead of sending to the grid during the day. As you say, if you get enough solar thats all good. If you dont then the HWS would also require additional power to heat the water - the cheapest version of this is off peak (controlled load).
        
        lgacb08 on 28/01/2025 - 19:25
        
        @Euphemistic: Mate, that was the original set up, but my solar collector has been removed and the tank works the same way as the off peak hws. In fact it had been working that way for a long time before I moved in because I just found out 6 months after moved in that the retic pump weren't working, as has been the case with lots of set up like this.
        Solar diverter was installed after solar pv installed (and hws taken out of controlled load) . So I've been through all that mate, don't come along lecture me based on assumptions.
        
        Euphemistic on 28/01/2025 - 20:51
        
        @lgacb08: Not lecturing you. Trying to understand what ypure posting. Youve just shifted the goalposts and not explained your setup properly. Why did you mention the solar collector at all?
        
        What does the HWS use as backup? Mains? You said the HWS requires 3600w fixed but solar might only procure 20o0w. How does that work? I'm also not sure why you think a HWS one runs once a day. It heats when there is power available and the water is not hot enough.
        
        You can put a solar divertor on with a controlled load.
        
        I know someone who, before solar, put a two way switch on a CL HWS. Meant he could flick the HW to mains if he ran out of hot water. Not legal, but the HWS worked fine.
        
        lgacb08 on 29/01/2025 - 11:52
        
        @Euphemistic: I wasn't shifting goalpost, in fact I didn't need to explain my setup but because someone failed to comprehend the basic principle of controlled load hws and starting to discredit my knowledge.
        Your questions above proved that. You better go on Google and search how solar diverter work. Catch power, mk2pv router and other terms might lead you to the right path.
        Technically you can put diverter on controlled load, aside from the legality of it, what benefits does that do when you're already on lower rates (but still no where cheaper than you own generation)?
        
        Euphemistic on 29/01/2025 - 11:59
        
        @lgacb08: When your export tariff is lower than the CL tariff why wouldnt you pump excess solar into the HWS? Instead of getting paid peanuts, put it to good use.
        
        Perhaps 'solar diverter' nomenclature is the problem. A was using it to describe a device that takes solar power the house isnt using and pushes it to a load, in this case HWS, instead of back to the grid.
        
        Our solar system typically exports less than what is required to heat the HWS, based on kwh from our bills. Ergo. A device sending excess solar to the HWS would require additional input - overnight. Again, this is from some time ago when bills were lower and the payback period for the diverter was something like 10y. I'm looking into what I can do to help lower bills again now.
        
        lgacb08 on 29/01/2025 - 14:44
        
        @Euphemistic: Yes, solar diverter diverts solar energy to hws, but it does more than just that, it account for days where solar output is less than your base load + hws load, which is usually a constant 1800, 2400 or 3600w load. And most importantly it won't let you import from the grid during these hours. Without it you don't have much room to wiggle, for a day like today.
        I don't know your solar set up so can't give correct advice, but if you exported less than what you use on CL then solar diverter isn't the right choice. But that must be very small system. A typical 6.6 kW system generate 8-10000kwh per year, a 300l tank probably only use 3000kwh per year. So on paper it's possible but need to manage carefully depending on your other electricity usage.
        As for your other question putting diverter on CL I'm confused because each statement contradict each other. You have to remember that controlled load usage is metered separately and you can't use solar to offset it. Normally If you use 3.6kwh at lunchtime to heat the tank, if solar generated 3kwh then you'd be billed 0.6kwh at full rate. If the tank is on CL, you will be billed 3.6kwh at CL and peanut for 3kwh fit (about 15c now), this is with the assumption that CL is on during this time. Do the math with your rates to see how much do you miss out on. So with CL approaching shoulder rate now it is never economical to stay on CL if your solar system can handle the load, the question is how much it cost to go that path.
        
        Euphemistic on 29/01/2025 - 16:40
        
        @lgacb08: So its not just a solar diverter. Its a power management system.
        
        You can run heating elements on low power, like a stove. If you have excess 2kw, you should be able to run the heater on 2kw even if its rated for 3.6kw then use grid power when its cheap to finish heating. At least, that was what was described to me when I first enquired. It seems tech had moved on.
        
        If you cant run the HWS at less than full power then it would seem inefficient to run it off solar if your house is using other power.
        
        lgacb08 on 29/01/2025 - 20:00
        
        @Euphemistic: Heating elements are inflexible because of ohm law applied to resistive load, they will draw a fixed amount of power, without diverter you can't get 3.6kw element to go down lower, it's either 0 or 3600w.
        
        ATTS on 29/01/2025 - 22:09
        
        @lgacb08: Just wondering any benefit keeping CL if no devices on it anymore
        
        Euphemistic on 30/01/2025 - 09:24
        
        @ATTS: If nothing on it, you should ensure you arent paying anything for it. If you arent getting charged on your bill, then probably not worth removing.
        
        ATTS on 30/01/2025 - 19:53
        
        @Euphemistic: Thanks
        
        So im paying 10c supply charge a day for CL. Im thinking like would the CL infrastructure could be repurposed for something else in the future.
        
        Also at 10c if i remember correctly i could have CL for around 10 years before reaching cost of removing the CL circuit by an electrician

Is It Worth Removing Controlled Load Meter if You Have Solar?

Comments

New Forum Topics