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  • My rooftop solar stats

    Some years ago I crunched a lot of numbers and concluded that financially it was not worth installing rooftop solar. It would never pay for itself.

    Then the prices began dropping rapidly, the systems got larger, and the Victorian government added its own $2500 rebate on top of the Federal government's.

    So a 6.6KW system started to look attractive and in October last year we had one installed.

    Cost installed including 5 KW inverter: $4690
    Less $2500 rebate $2190.

    So out of pocket for me $2190.

    From now until around May next year our daily solar output will exceed our draw from the grid, and the surplus will be sold at 12 cents a kw.

    Some figures:

    In the last 36 days, we have sold 570 KW to the grid for $68.
    We have bought 369 KW from the grid for $107.
    The 570 KW we sold was surplus -- there would have been hundreds of other KW we generated and used ourselves.

    January 2019 our biggest summer electricity use month, we bought 160.3KW, but sold 750 KWs.
    January 2018 without solar, we bought 592KW.

    August 2018 (pre- solar)
    Bought 876KW
    Sold 0
    Net 876
    August 2019 (with solar)
    bought 665 KW
    sold 218 KW
    net buy 447KW (so a little over half as much as without solar)

    We generate much more than we sell, but the figures I have are for what is sold as surplus to our own needs.

    Our biggest user is the reverse cycle air conditioner. Yesterday where in Melbourne we froze around 12°, it was on from around 8 am to 10.30 pm, consuming 19 KW of power. We generated about 18 Kw, most of that was used by the air con, tv, etc, and a surplus 4 KW sold into the grid.

    The Solax inverter sends a wifi signal to my router for access anywhere in the world through a portal, giving real-time statistics on electricity being generated, panel volts, grid voltage... We love looking at all that nerdy stuff.

    Is it green?

    In the last 12 months, we have saved 8.6 tons of carbon emissions.
    We have "planted" 23.2 trees
    It has yielded 8.6 megawatts of electricity.

    The proliferation of daytime solar has given incompetent governments who have failed to give us the power we need by building power stations, a breathing space -- tiny but maybe enough.

    However, this proliferation is providing headaches for power suppliers. All that unused electricity being fed into the grid is not under their control, causing irregular voltage. They can turn street transformers up or down somewhat, but in the future it will be an alarming problem with almost catastrophic technical consequences.

    Our inverter will switch off if the grid voltage reaches 260 -- and we come close very often.
    At 10.24 this morning grid voltage was 253.4 -- just 7 volts off.

    Power bills: We hate the way power companies keep changing plans. A year ago we could have sold power at 20 cents a KW. Now, after government meddling, it is a flat 12 cents. The price we pay for a KW though is three times that much.

    Our bills have reduced dramatically. One quarter we were $3 in credit.

    Personal future problems will be the slowly declining panel output, the inverters are a weak link, and replacement costs are very high. Without the inverter, output is cut to zero. When grid power is cut for maintenance, our inverter shuts down and we have zero power. (we do have petrol generators on standby).

    Battery storage: too costly to be worth considering now.

    For all that, we love our panels. Even though they are extremely inefficient. For every 100 watts of sunshine power that falls on every square meter of panels, just 17% or so is generated as electricity. They are improving, but very slowly.

    Hope these figures prove helpful.

  • #2
    I've just ordered ours here in Perth. Our feed in tariff is only 7c per unit here. Speaking of units... you're using 'KW' for 'kWh'. kW is a measure of power, ie the rate at which work is being done. kWh is a measure of work done, ie using a power of one kW for one hour, also called "a unit". Your panels have generated 8.6mWh of electricity.

    Other annoying things about power here in WA (in addition to the measly 7c/unit FIT)
    Maximum 5kW inverter (with max 6.65kW panels attached) for single phase
    If you have three phase power you're allowed more capacity... but only as approved by Western Power, so they can avoid suburbs going too voltage-high. That's reasonable, although I would prefer to see a system that encourages all the solar you want and solves the over-voltage in a different way. The unreasonable part is that Synergy (the monopolistic power seller in Perth) will not pay you for any of you exported power if you have more than 5kW of inverter capacity. They'll just steal it. This was probably signed into law by a government that wants to maximise profits for the power selling utility before privatising it in a few years.

    I went for an expensive system, with 25 years parts/labour/performance on panels because I detest the idea wasting time doing it all again in 10 years, also I don't like the idea of putting all those panels in to landfill. So I got 20.4% efficiency panels, which may help with roof space down the track if I decide to double or triple my capacity.

    My payback is 3.4 years... in theory. Estimates by solar installers vary wildly, and the online solar calculator I used is clearly oversimplified.

    Hopefully in 5 years or so it will be viable to add a battery and save the 'other half' of my power bill. My usage is high from too many computers and aquariums and ponds.

    But today in pretty much every state it's a no-brainer to install solar, for most people it's a 20% to 40% yield on investment.

    I could even install battery right now and still have a 7 year pay back... mainly due to my too-high usage. But it's not a good enough return to tempt me, especially when everyone thinks battery technology/scale will improve within 5 years or so.

    Comment


    • #3
      Originally posted by robusto View Post
      Cost installed including 5 KW inverter: $4690
      As a side note as much complaining as is heard over the high prices paid in AUS as compared to the US here is a case for people to jump up and down and celebrate. The average 6kW system installed in the US costs over $AUD30,000.


      Java "The great rip-off" phile
      Toys! I must have new toys!!!

      Comment


      • #4
        Originally posted by Javaphile View Post
        As a side note as much complaining as is heard over the high prices paid in AUS as compared to the US here is a case for people to jump up and down and celebrate. The average 6kW system installed in the US costs over $AUD30,000.


        Java "The great rip-off" phile
        More like half that... 12.5kUSD
        https://news.energysage.com/how-much...st-in-the-u-s/

        Comment


        • #5
          A question that probably highlights my ignorance, but why can't excess electricity, generated by the proliferation of solar panels, be used to pump water back up into dams for night use?

          Comment


          • #6
            If I recall correctly, without Federal and state government subsidies our 6.6kw system would have cost around $11,000 instead of $2190.

            Comment


            • #7
              OCD, not every dam is equipped for hydro would be one reason. And we haven't yet reached that critical overload stage, especially in Victoria where 1600 MW which Hazelwood generated, suddenly disappeared with so little of it replaced.

              Even with so much rooftop solar, this summer will again be touch and go for supply to meet demand. No doubt polluting, costly diesel generators have been hired to be on standby.

              Comment


              • #8
                Originally posted by theonetruepath View Post
                That price is after tax credits, which depending on your tax situation you may or may not receive. Per that site the pre-tax credit price is $USD17,940 which at the current exchange rate* is $AUS26,066

                If you want to talk after tax credits/rebates Robusto's 6.6kW system w/ 5kW inverter ended up costing him $AUS2,190. Per the site you linked to (There are others who state higher average prices such as the one I used.) the quoted $USD12,588 after tax credits for a 6kW system converts to $AUS18,246, over 800% more than Robusto's cost. So the ratio is showing an even better price for Oz than when comparing the before tax credit/refund prices.


                Java "Apples to apples" phile



                *Note the exchange rate used is the bank rate which none of us get so the actual price paid would be higher.
                Toys! I must have new toys!!!

                Comment


                • #9
                  A word of caution to look at green tech on Whirlpool. Many happy posters with solar but some have found their supplier has crashed by the time the first inverter dies and the expected warranty claim can't be made.
                  I suggest the status of the supplier is just as important as a good price.
                  Have fun.

                  Comment


                  • #10
                    I paid $3700 for a Huawei 5kW inverter with 6.6kW of panels split NW/NE.

                    They have been in for going on 18 months and are great. The inverter is lovely and only 10kg, fanless with great software to analyse everything. I can also log on and do firmware updates myself.

                    Nice.

                    In Perth the payback would be between 2 and 3 years for that.

                    Comment


                    • #11
                      Half my power bill is the service charge. Half of my usage is the fridge keeping my ice blocks frozen at about 50c per day.
                      Im thinking of disconnecting the power and using a lng converted generator and a battery.

                      Although, most of my lng bill is probably service charge too... Maybe I need to convert everything to lpg salvaged from wrecked cars...

                      Comment


                      • #12
                        Originally posted by Javaphile View Post
                        That price is after tax credits, which depending on your tax situation you may or may not receive. Per that site the pre-tax credit price is $USD17,940 which at the current exchange rate* is $AUS26,066

                        If you want to talk after tax credits/rebates Robusto's 6.6kW system w/ 5kW inverter ended up costing him $AUS2,190. Per the site you linked to (There are others who state higher average prices such as the one I used.) the quoted $USD12,588 after tax credits for a 6kW system converts to $AUS18,246, over 800% more than Robusto's cost. So the ratio is showing an even better price for Oz than when comparing the before tax credit/refund prices.


                        Java "Apples to apples" phile



                        *Note the exchange rate used is the bank rate which none of us get so the actual price paid would be higher.
                        You said "The average 6kW system installed in the US costs over $AUD30,000"
                        The average price for 6kW which of course includes tax credits is 12.5kUSD. If not everyone gets the credits then that bumps the average up a bit, ie to 12.5k. It's already factored in. That's 18kAUD which is closer to half of "over $AUD30,000"
                        Not sure what web site you can point to that gives a figure over 30 000AUD. The site I gave specifies prices for systems using individual panel manufacturers, only one that I could see charges as much as that for a 6kW system. They charge like champions though, at 30kUSD for a 6kW system.

                        Comment


                        • #13
                          Jackster....I presume you don't live in a suburb with neighbours just an arm's length away then

                          Comment


                          • #14
                            Originally posted by theonetruepath View Post
                            You said "The average 6kW system installed in the US costs over $AUD30,000"
                            The average price for 6kW which of course includes tax credits is 12.5kUSD. If not everyone gets the credits then that bumps the average up a bit, ie to 12.5k. It's already factored in. That's 18kAUD which is closer to half of "over $AUD30,000"
                            I provided a comparative price that was the same as the price I quoted from Robusto's post:

                            Originally posted by robusto View Post
                            Cost installed including 5 KW inverter: $4690
                            i.e. the installed price,which was not the price including the tax credit/rebate:

                            Originally posted by robusto View Post
                            Less $2500 rebate $2190.
                            I used the same pricing format as Robusto/the quoted post did.

                            An Installed Price is not the same thing as a Final Price/Price After Rebate unless the rebate is an instant one given at the time of purchase. Given Robusto's wording it was a fair assumption that the rebate was similar to the Tax Credit in the US which is filed for as part of ones Federal Tax Return in the following year.

                            Originally posted by theonetruepath View Post
                            Not sure what web site you can point to that gives a figure over 30 000AUD. The site I gave specifies prices for systems using individual panel manufacturers, only one that I could see charges as much as that for a 6kW system. They charge like champions though, at 30kUSD for a 6kW system.
                            Did you not read my 2nd post which you quoted in the above post? I gave you the link to the web site I got my figure from:

                            Originally posted by Javaphile View Post
                            (There are others who state higher average prices such as the one I used.)
                            Which if you go to and tell it to display the average cost before tax credit for the 6kW system you will see a price of $20,331 which is of course in USD. Using the exchange rate at the time of my posting ($AUD1=$USD0.68824) that converts to $AUS29,540.57. As noted at the bottom of my 2nd post that's the bank rate not the rate you or I get. If you add on those extra points that you and I pay that puts the price over $AUS30,000.


                            Java "Wording matters" phile
                            Toys! I must have new toys!!!

                            Comment


                            • #15
                              State government subsidies in Australia vary among the 6 states and can be in the form of direct cash to the household (in my case here in Victoria) to interest-free loans or subsidised battery.

                              In practice, the Federal government subsidy is usually paid to solar installers who then quote an after-subsidy installation price.

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