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Use of spare 500 Watt from Solar Panels

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  • #16
    Originally posted by LucMan View Post
    The net metering usage here is calculated month to month, you can carry credits for 1 year from your anniversary date. If you then still have kwh credits the utility pays you the wholesale rate for those credits.
    Any consumption over the amount of power produced every month is billed at approximately 20 cents a kwh total for supplier and delivery.
    If the utility is billing for instantaneous consumption and production that doesn't make a lot of financial sense to install pv as you are paying retail and selling at wholesale rate.
    What's the advantage?
    Keep in mind that the OP doesn't live where you live.

    Net metering rules vary by the locality, and it sounds like where the OP lives (Australia), the rule is that exported power gets credited at a lower rate than the price for purchased power.

    So it makes sense to use excess power to offset later usage, rather than export it to the grid.
    16x TenK 410W modules + 14x TenK 500W inverters

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    • #17
      After some research i believe I was WRONG in how in how I thought the system worked, so my apologies to Solardarity.

      In Australia, which is where the OP is, You do not get a credit of KWH for your grid connect production, you get paid for it.

      In the OP case they get paid 5c KWH for solar production and pay 28c KWH for mains power.

      This is my new understanding, You only export if you are not using what the solar is producing. So "In a perfect world" if the OP has a 2kw system and is only using 1.5kw of what it is producing then .5 will be exported.

      So if Op could put a 500w element in the hot waster system then is could used that to heat water.

      I dont think it is really practical or cost effective. OP does not want to put a 500w element in and Im not sure if one is even available, and I dont think it would be practical because if you did want to heat water fast you would be unable to.

      One possible, but not really practical way, if you really want to utilise the power, is when there is good solar production turn everything else off and turn the hot water on.

      PS: Australia is 240V 50Hz, Not sure what size system solardarity has.

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      • #18
        My electric had 2 elements. You could get half way there, by putting the 2 elements in series. Bruce Roe

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        • #19
          Originally posted by Bala View Post
          So if Op could put a 500w element in the hot waster system then is could used that to heat water.
          Electric Hot Water heaters have an lower and upper element. Both operate at 240 VAC. Lower element depending on model is 1500 to 3000 watts, upper element 1000 to 2000 watts.

          What happens when you replace them with a 500 watt element? Cold Showers

          What happens when you add an extra 500 watts? Explosion if the thermostat pressure regulator fails.

          There is nothing to gain. Solar power is extremely dynamic and there is no way to be able to design something that can track and utilize the excess power. Excess power can be 10 watts at one second and 500 watts the next second.
          MSEE, PE

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          • #20
            Originally posted by Sunking View Post
            Electric Hot Water heaters have an lower and upper element. Both operate at 240 VAC. Lower element depending on model is 1500 to 3000 watts, upper element 1000 to 2000 watts.

            What happens when you replace them with a 500 watt element? Cold Showers

            What happens when you add an extra 500 watts? Explosion if the thermostat pressure regulator fails.

            There is nothing to gain. Solar power is extremely dynamic and there is no way to be able to design something that can track and utilize the excess power. Excess power can be 10 watts at one second and 500 watts the next second.
            Not all hot water systems have 2 elements, it just depends on the size of the heater.

            I dont believe its practical as I said, but if it were done, it would no different to anything else running, if there was not enough solar it would run of mains, OP is not talking to disconnect the solar from the grid and run purely off the solar, just utilise solar generated instead of feeding it to the grid.

            Anyway, I have learnt something from this.

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            • #21
              Originally posted by bcroe View Post
              My electric had 2 elements. You could get half way there, by putting the 2 elements in series. Bruce Roe
              If you had a 2000W heater with the two identical elements in parallel, then if you keep the voltage the same and put them in series you now have a 500W heater.
              If you had a 2000W heater with two 2000W elements which never run at the same time, then if you rewire them in series you get 1000W.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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