Electric Hot Water on Controlled Load Tariff Vs Solar

virhlpool on 13/02/2024 - 21:12
Last edited 14/02/2024 - 07:53

My place has a large'ish solar panel system (12kW) which I am not able to utilise fully (from export perspective) on hot days due to the 5kW/hr export limit applied by my distributor Endeavour. My electric hot water system is connected to Controlled Load which enjoys a bit lower tariff than normal but it isn't connected to solar, I assume [correct me if I am wrong, but I assume that any controlled load is by default not connected to solar].

i) For reference, here is my Globird Energy electricity bill for 20 days period (Jan/Feb) before I moved to Red Energy recently. As you can see, controlled load rates are only slightly lower than offpeak rates.
ii) This is my hot water system.

Hot water usage is spread across the day for showers, washing utensils, washing machine (I guess this can be avoided if I remove hot water supply to the machine and let it heat the water with the inbuilt system using electricity). I am not sure if I should keep my hot water system on a controlled load tariff or move it to solar/ peak and off peak tariff. I don't have solar production data from the seasons other than summer yet. Given the above info, can someone who is familiar with this please advise?

If I should move the hot water to solar, how do I make sure that the heater (especially my heater type) works mostly during day hours - does it warrant use of a timer? Where and how can I use the timer?

Also, how much would a sparky charge to move the hot water system from controlled load to the normal tariff?

Thank you!

Home & Garden

Comments

  • kipps on 13/02/2024 - 21:32
    +1

    Look up the Catch Power. Worked out great for me. No point paying for controlled load with large PV arrays.

    • virhlpool on 13/02/2024 - 21:33

      What's the solar in feed rate? I get 7c with Red Energy.

      • kipps on 13/02/2024 - 21:34

        I don’t know what you mean. Each distributor will have different controlled load & FIT rates. I don’t have controlled load. FIT is 3.85c and usage would be 24ish. I’m far better off with HWS using PV.

        • virhlpool on 13/02/2024 - 21:40

          What did you use Catch Power for exactly? I am trying to understand its application.

          • kipps on 13/02/2024 - 22:08

            @virhlpool: Catch Power sends power to hot water system when PV would otherwise be exported. You don’t use power from grid to power a tank unless the thermostat hasn’t cut off all day.

            • virhlpool on 13/02/2024 - 23:40

              @kipps: Thanks. Can one not just move HWS to normal tariff (from controlled load tariff) and it would do the same thing without Catch Power, which seems to be $750 at least plus sparky fee?

              • SBOB on 14/02/2024 - 06:25
                +2

                @virhlpool: You, at minimum, need a timer to stop your hw system turning in during non solar hours, and therefore drawing power from the grid

                The catch power is a smart timer that's able to detect solar export and control the HW system to only operate during excess solar time, plus regulate/restrict power to the hw system to keep its power draw within whatever your Pv excess is

                With such a large array though you'd likely get the majority of the benefit with a timer restricted to excess solar hours, and you'd need to do the sums on the extra benefit if the catch power vs payback period

                • virhlpool on 14/02/2024 - 07:47

                  @SBOB: Thanks! How will the HWS work outside of the time set by timer OR it simply won't work? e.g. If the system needs to heat water in night, would it still work fine?

                  • kipps on 14/02/2024 - 08:43

                    @virhlpool: You usually get an override switch with these solutions so that if the HWS tank runs out you can force it on. Catch power green, for example, has a boost button.

                  • SBOB on 14/02/2024 - 12:33
                    +1

                    @virhlpool: Hw storage systems should be large enough to cover hot water for the period between daylight when it is then reheated again.
                    It must be as it's already doing that just during night time control load periods.

              • kipps on 14/02/2024 - 08:44
                +1

                @virhlpool:

                Can one not just move HWS to normal tariff (from controlled load tariff) and it would do the same thing without Catch Power

                If you don't have a device controlling the HWS then you'll be paying normal tariff rates at night when the HWS heats your tank immediately after you shower at night. You really need to do more research about how a HWS works.

    • ATTS on 15/02/2024 - 20:54

      Could you explain more about catch power to a newbie?

      My solar hot water system is old but it is on control load and solar powered

      I also have a newer seperate 8kw solar panels

      Trying to save on electricity

      Im thinking getting a timer on my current hot water heater element

      Or upgrade to a newer" heat pump" hot water

      What do you reckon is best cost wise?

      Cheers in advance

  • altomic on 14/02/2024 - 08:46

    can you install a solarhart roof system ?

    I didn't connect mine to power when I replaced it (with a second hand system) 4 years ago. (needs a new thermostat - which I have, but haven't gotten around to fitting)

    just the sun keeps it hot.

    ran out of water once for a day. not optimal but I haven't paid for electricity to keep water hot for 4 years - so the trade off is in my favour.

    • SBOB on 14/02/2024 - 12:32
      +1

      In general, roof space is better used for a solar PV system than just dedicated to a solar hw system

      Especially considering the op already has a sizeable PV system and working elec hw storage system, replacing their hw system would likely be a less efficient use of their $

  • Euphemistic on 14/02/2024 - 14:44

    The 'timer' for controlled load is in the meter box afaik. The HWS is just a dumb heater, if its got power and the temp is too low itll heat. On controlled load, the power is only turned on when the power company wants. Change that to solar and it should only heat if it needs AND the sun is shining. Only problem is if there isnt enough solar to supply everyrhing youre using in which case it will pull from the grid at whatever rate you pay. Ypu lay also want to set a timer or similar so it can only heat during daylight hours.

    I looked I to putting a solar diverted for our off oeak HWS. Wasn't worth it because most showers are at night and we'd want controlled load to heat it over night just encase the sun don't shine. In that case we'd hardly need solar heating.

  • AB100 on 14/02/2024 - 17:23
    +1

    I installed a contactor in the fuse box on my hot water circuit, and then installed a Shelley Pro 1 timer to switch the contactor, onto the main power circuit (all done by an electrician).
    The Shelley Pro 1 can be connected to your internet, either through WI-FI or a network cable, and allows me to program it's operation using my phone, and if needed I can override the timer using the phone, without having to go to the fuse box (it also works when you're away from the property).
    I did have to swap out my 3600W hot water heating element, and replace it with an 1800W unit, as the hot water system was using more power than my solar system was delivering (Just takes roughly twice as long to heat the water now).

    • virhlpool on 14/02/2024 - 18:55

      How expensive was this? Timer and the electrician cost, I mean.

      • AB100 on 14/02/2024 - 20:02
        +1

        Sorry it's actually Shelly, not Shelley.
        I bought the Shelly Pro 1 off of Amazon for $89 delivered. You can pick them up for $75 plus postage elsewhere, but once I added postage costs, and delivery timeframes, it was easier and a lot quicker to get it from Amazon. The contactor was just over $40, and I paid about $45 for the 1800w heating element (both from my local electrical wholesaler). Total install time was 1.5 hours for the electrician.
        This whirlpool forum has really helpful information about using the Shelly Pro for a hot water timer, and how the programming works.
        https://forums.whirlpool.net.au/thread/9vw4xj02
        I was a little concerned about whether there would be interference with a WI-FI signal being sent from the fuse box, but I've had no problems at all.

  • Cheapshots on 14/02/2024 - 19:14
    +1

    You also need to calculate your return in investment as well if the install costs a bomb.
    How long will it take in solar savings to earn the $850ish for the install.

    I had a heat pump hws replace an electric and just put it not on controlled load. Set a timer on the unit to just run in “sun” hours. Sure it runs on cloudy days but no other choice. Most of the time it’s free. Easier then paying $800+ for a formal solution in the switchboard

    • virhlpool on 14/02/2024 - 19:27

      Cost of timer + Sparky fees to change HWS from Controlled Load to normal supply and install timer -> I guess this is all you would have spent. Still not super cheap. Right? I am trying to figure out how much it would cost.

      • SBOB on 14/02/2024 - 20:02

        Cost of timer + Sparky fees to change HWS from Controlled Load to normal supply and install timer

        Its not a time consuming job if you just want a timer installed.
        Budget $350 if thats all you're calling out an elec for. That would be my rough guess ball park

        Do the sums
        If you're paying a controlled load fee per day - x
        Difference in kwh price between your FIT and your controlled load rate - y
        Being controlled load you can work out exactly how many kwh you use a month - z

        Cant see if you have a controlled load fee, but based on your screenshot you'd save $1.75/day in elec costs

        148kwh controlled load usage over 20 days
        ~7.4kwh per day for hot water
        $0.2366 difference per kwh for what you pay to import controlled load power compared to the 5c you;ll lose from exports
        =$1.75 per day you would 'save' if you could move all your hot water to PV generation

        Even the $750 catch power would pay for itself in ~ 1.5 years.

        a ~$350 timer only install would be covered in less than a year

      • AB100 on 14/02/2024 - 20:18

        The hot water is still attached to the controlled load, and the contactor is on this circuit. The Shelly Pro 1 is on the normal supply circuit, as it needs 24/7 power. Shelly Pro 1 switches the contactor on and off, but power for the hot water system still comes from the controlled load. I.E. Controlled load - Contactor - Hot water system.
        You don't have 24/7 hot water power supply in this situation, as your still beholden to the times that your controlled load is available.
        My power company turn off my controlled load from 4pm to 10pm each day.
        I have my Shelly Pro 1 setup to turn on at 10am and turn off at 4pm, though it rarely takes more than 4 hours to heat my tank.
        The advantage of leaving the hot water on the controlled load is that if you use all your hot water in the evening, and need hot water first thing in the morning, you can just override the Shelly timer, and heat the hot water during the night on your cheaper controlled Load tariff.

  • dust on 15/02/2024 - 11:39

    Have you considered changing your hot water to electric heat pump? Some states have rebates for it.

    Electric heat pump set to turn on during solar generation times would be the most efficient. But of course you have to consider the initial outlay.

Login or Join to leave a comment
Login Join