How Homes with Solar Panels Billed

malkakas on 27/04/2017 - 15:41

Hello Ozbargainers,

I am trying to make a decision on weather to install solar panel on our roof or not.

What I really need to find out is how the billing works with solar panaels.

Here's some details about our electricity usage.

We are a family with 3 bedroom house. Gas is used for Cooking and Hot water syetem.

Our daily electricity usage is around 18KWh, around 8 KWh is used in the day time, around 10KWh is used at night.

We have an elderly relative living with us who hates cold weather, therefore we only use A/C when it is extreamly hot (i.e: when outside is above 35C or so).
But at the night time heating is used more often.

If I install a solar system that is capable of generating 20KWh during day time,

8KWh out of generated 20KWh is going to be used within the house and remaining 12KWh will be exported to the grid.
Then at night I have to pull 10KWh from the grid for our night time use.

Lets assume that I have net metering installed with 6 cents Feed in Tarriff and Flat electricity rate 35 cents.

how my electricity bill will be calculated?

Thanks in advance.

Home & Garden

Comments

  • Gershom on 27/04/2017 - 16:07
    -1

    You will be charged a higher tarrif for what you use. The difference will be more than you get from feed in. Overall you will lose money. It's for mugs.

    • Euphemistic on 28/04/2017 - 07:49

      But every kW you generate and use (not export) is 'free' electricity. I use quote marks becuase of course you have had to install the system at a cost so the electricity is not free, but you can work out how much the power you generate does cost.

      Our grid usage has dropped from around 26kwh to around 17kwh, plus we are exporting excess generated power since installing our system. That has dropped our bill significantly.

      You don't install solar panels to export to the grid anymore, but aim to use what you generate as feeding to the grid at 6c/kWh is a rort by the elctricity companies.

  • Nugs on 27/04/2017 - 16:18

    i'd be surprised if it is worth it with current rates.

    when we researched (& installed) five years ago, I used this web site

    https://www.solarquotes.com.au/calc5/

    .

    • ESEMCE on 27/04/2017 - 16:37
      +2

      8kWh daytime usage is potentially worth it. But you don't need 20kW of panels (that's a lot of roof space and a lot of extra expense in inverters)! Probably more like 5-6kW.

      I would recommend you do further analysis… Get a whole home energy monitor installed now and have a look at the pattern of usage through the day.
      How is that 8kWh daytime usage split across the day?
      In my house we have peaks at Breakfast and Dinner and we have changed our routine to use high consumption appliances like Washing Machine and Dishwasher through daylight hours too.

      But I have only North and West facing panels…
      The West panels cover our Dinner usage (mostly), but the North panels don't kick in until 9am, generally after Breakfast time. I regret going with the installer's advice and installing them North instead of East as I was originally planning.
      My panels produce a Bell curve of generation, so early in the morning, or late in the afternoon our usage can peak above our production especially for high power appliances like oven/kettle/toaster/coffee machine.

      Forget the money you get from feed in, it's essentially irrelevant. The only relevant factor is how many kWh of usage you can push into daylight hours, every kWh you can supply with Solar is 35 cents "saved" or paid off your Solar install…
      So if you can squeeze 6kWh of your 8kWh daily consumption to be supplied from your solar you'd "save" $2.10/day $766/year assuming it was never cloudy and you had the same number of daylight hours every day (which of course is not true)… So maybe $500/year in the real world.

      • mskeggs on 27/04/2017 - 16:50
        +2

        With your usage, a 2kW system will cover the daytime, but since a 3 or 4 kW is not much more, you might as well get that to get some benefit on days you use more power (e.g. weekends etc).
        If you were able to shift some of your night load to the day, that would also be good (run the dishwasher/washer etc. in the day where you can).
        You will pay for any electricity you consume from the grid, and get credited for any excess you produce, but obviously buying at 35c and selling at 6c.

        The rule of thumb is 1kW of panels will produce an average of 4kWh per day.
        It will take around 5 or 6 years to pay back, depending on the purchase price and how much power you can offset during the day.

      • Euphemistic on 27/04/2017 - 21:36

        20kwh is what was aimed at. Depending on location that could be 4kw of panels. Our system is nominally 4kw and gets up to 25kwh in summer, bit less in winter, but I haven't really got those numbers yet.

        • ESEMCE on 28/04/2017 - 07:38
          +1

          In SA, he'll need closer to 10kWh panels to get 20kWh in Winter, but I don't think OP needs 20kWh daily production anyway.
          Really just needs a guaranteed (clouds permitting) 8kWh.

        • Euphemistic on 28/04/2017 - 07:42

          @scubacoles: 10kw panels, not 10kwh panels.

        • ESEMCE on 28/04/2017 - 08:27

          @Euphemistic: Yep ta.

      • malkakas on 28/04/2017 - 13:04

        Hi,
        I checked the https://pvoutput.org for the solar panel owners living in nearby postcodes and saw how much they produce per day.
        I think 5 or 6 KW system would generate 20KWh (or close to that in winter).
        But I used 20KWh per day to make it easier to do the math.

        It seem during Colder months (May, June July) solar panels produce around 2.5-3KWh per installed 1KW solar panel.

        During April, August and September solar panels produce around 4KWh per installed 1KW solar panel.

        During day light saving months (October to March) solar panels produce over 6KWh per installed 1KW solar panel.

        By the responses I see that I only need to install the panels to cover the daytime usage.

  • ozzie freddo on 27/04/2017 - 19:27

    Where you are makes a big difference, so what state are you in? and who is the wholesaler for your area? and do you have a smart meter?

    • poboy on 27/04/2017 - 21:55
      +1

      Poster is from SA. Click on their name to check.

    • malkakas on 28/04/2017 - 13:08

      I live in SA. Adelaide metro area.

  • malkakas on 28/04/2017 - 13:17

    Thanks for the responses folks.
    I got a "solar perfect" north facing roof that get sunshine all year round.
    It can easily hold 40+ panels (if required) and I was really thinking on placing a massive solar system.

    However it seems a big solar system is not worth the cost as I only use around 8KWh(max) during day light hours.

    May be I will consider a 2 or 3 KW system.

    • Euphemistic on 28/04/2017 - 16:10
      +1

      If installing now, consider future proofing a bit for battery storage. There probably wont be much difference in price between a 2-3kw system and a 4-5kw system. Depends a bit on how many $ you have available

      • malkakas on 28/04/2017 - 17:09

        Thanks. I'll get few quotes before making a decision.

    • ESEMCE on 10/05/2017 - 09:59

      Just factor in that your "solar perfect" roof is only going to start producing usable power between 8am-4pm in Winter, probably outside your high usage.
      North facing roofs are only solar perfect if you're getting paid decent money for your production or have unusual usage patterns.
      Based on the current financial model where you get paid a pittance for feed-in, East/West (predominantly West) panels are arguably more solar perfect as they will generate usable energy earlier/later in the day during the times where you use more power anyway.. ie Cooking Breakfast, starting Laundry, cooking Dinner.

  • ESEMCE on 10/05/2017 - 10:02

    One other factor to consider, get on the roof and check out any shading from trees, stobie poles, plumbing vents, chimneys, AC units etc…. even a sliver of shade over a single panel kills production of the entire bank of panels unless you go for a micro-inverter solution.

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