Adding Solar Panels To Existing System? Here’s What You Need To Know.

solar panels with space for adding more

Here are your options and gotchas when adding solar panels to an existing system.

So you’ve got solar panels on your roof and you want more so you can get your bills even lower?

(Note: If you are on a premium feed in tariff then you need to understand how solar upgrades can affect your eligibility. 

If you are on the NSW solar bonus scheme, then your FiT is ending on 31 December 2016 – and you should time your upgrade to happen as close to this date as possible)

You are probably weighing up 3 alternative approaches to your solar upgrade:

1) Add more panels to your existing system – using your original inverter.

2) Get a new, bigger inverter and add more panels too.

3) Get a whole new separate solar system installed next to the original.

Let’s go through each option in detail so you can weigh up the best approach for you.

Option #1 Adding more panels to existing system using your original inverter.

The first thing to be aware of (and not a lot of people know this) is that you are allowed to have a panel array with a peak power up to 133% of your inverter’s rated peak power.

For example:

If you have a 1.5kW inverter, you can have up to 2kW of panels attached.

If you have a 3kW inverter you can have up to 4kW of panels attached.

If you have a 5kW inverter you can have up to 6.65kW of panels attached.

And if you don’t go over the 133%, you can claim the solar rebate (STCs) on those extra panels which will cover a big chunk of their of their cost (excluding installation costs and installer margin).

So if your inverter is big enough, adding panels is a cost-effective option to get more energy. You may be wondering how on earth this can be the case if the inverter limits the power output. Let’s use a 3kW inverter as an example.

3kW of panels will generally only produce 80% (2.4kW) of their rated peak power due to losses.

4kW of panels, after losses will produce a peak power of 3.2kW. A 3kW inverter will safely clip this down to 3kW. So you are only losing 0.2kW of power. And that is only for a couple of hours each side of midday on a summer’s day. In the mornings, evenings and winter the peak power will be way less than the rated 3kW of thew inverter.

So oversizing your inverter by 133% is a good way to squeeze more energy from it.

Two big caveats here are that:

1)Unless your original solar installer does the upgrade you will void your existing system warranty.

2)It depends on your installer finding the same or very similar panels to your existing ones.

If you want more panels than your inverter can handle (using the 133% rule), or you can’t find compatible panels, then your next option is:

Option #2 Replace your small inverter with a bigger inverter and add panels.

It seems like a waste of money and resources to remove a perfectly good inverter.  However the sad truth is that over the last 7 years a lot of the installed inverters that have been cheap and nasty and are probably on their last legs. If your inverter is a Sunny Roo, KLNE, JFY, JSI, Aerosharp, Sharp, or other inverter with a penchant for going bang after a few years, then this is a great opportunity to replace the thing with a genuine premium inverter, such as SMA.

Another reason to bite the bullet and swap your old inverter for a new bigger one is that one inverter is much easier to add batteries and backup to than two separate ones. So if a battery ready system with backup is a priority, having a single, large inverter is the way to go. (This post explains what a battery ready system with backup is and how that differs from a battery ready system without backup)

If you do decide that up-sizing your inverter is the way to go then watch out for these gotchas:

a) With panel technology changing so quickly, you may struggle to find extra panels that match your existing array. In this case get an inverter with 2 or more inputs so you can install new, different panels without affecting the old array.

b) If possible get the original company to do the work, then they keep the responsibility for the system warranty.

c) I recommend getting an inverter with SUNSPEC/MODBUS. This is a communications protocol that will make it easier to add batteries in the future. All the SMA models on sale now in Australia have this baked in. I would say that SMA are the safest bet here.

Note: ABB inverters can also talk MODBUS with a $500 interface box. And although the Fronius data sheets seem to claim all their inverters talk MODBUS, the word on the street is that in practice it is only usable in their expensive ‘hybrid’ models. Perhaps some one from Fronius would like to comment?

d) You can’t claim any rebate on the inverter, but you can claim the solar rebate on the panels. So put as many panels as you can on that inverter (133% of inverter rated power) because the rebate (STCs) covers a large chunk of their cost.

If you don’t want to replace your existing inverter, then your third option is:

Option #3 Get a whole new separate solar system installed next to the original.

This option can make a lot of sense – if batteries with backup are not on your radar. You get a new system, with a separate warranty. And because installers are so efficient at installing whole systems, and don’t have to fiddle around integrating into existing solar wiring, it can often work out cheaper than upgrading your existing system. And yes – you can claim the solar rebate (STCs) again on your second system – it will already be included in any quoted prices.

So to summarise:

Be aware that you can legally oversize most inverters by 133%. This may give you all the energy you need with your existing inverter.

If 133% of your inverter rating is not enough, then you can replace your inverter to allow you to add more panels. Just be aware that this can be surprisingly expensive as it is not as straightforward as a fresh installation.  If you are getting a new inverter ask for one with MODBUS/SUNSPEC communications as it will be easier to add batteries to in the future. And if the original company does the work then your warranty should stay intact. You do waste your old inverter though.

It is often cheaper to add a whole new solar system using either a conventional string inverter or micro inverters . In grid connect mode these 2 systems side by side will work great, but it can make adding batteries+backup more complicated down the track.

And I’d be remiss if I didn’t mention that you can get quotes for a solar system upgrade using my free service here.

About Finn Peacock

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and founder of My last "real job" was working for the CSIRO in their renewable energy division.


  1. Hi, I bought a 1.5KW solar system from True Value Solar six years ago. Originally it had a Chinese made Aerosharp inverter. It failed about six months later. After much pressure to True Value Solar, they replaced it with the Growatt brand. So far so good, although it does interfere with my AM radio stations sometimes.

    • True Value Solar installing cheap junk? I’m shocked!

      • david milner says

        Hi Fyinn, A friend has a 1.5 KW system with an AeroSharp Inverter which has died after a long life. I’ve located a 2KW AeroSharp and would like to add a few of extra panels up to the 2KW. I assume that these are pretty old tech panels so I guess I need to look on the used market. Any suggestions as to where I may find such panels?

        • Ronald Brakels says

          Hi Dave, Ronald here.

          I’m afraid I don’t know good places to check for second hand panels. But I suppose you could look in the usual online places – Gum-bay or e-tree or whatever they’re called. While it’s best to have the same type of panel it’s possible to get by with something of the same wattage. You can use slightly higher wattage panels if you have to, but the extra energy they generate over the weakest panel in the string will be dumped as heat which isn’t good for their long term reliability, so it’s best avoided if possible.

          If that inverter you found is old it may not meet current standards and can’t be connected to an on-grid system, so that’s something to be considered.

          • david milner says

            Thanks for the info. I’ll have to pop up a ladder and check what panels are up there.


    • Michael M says

      I got a 2 k in Sydney the mob who installed it (Nicholls group) wanted to charge me when the inverter died but the manufacturer told me these were so new they had to be under warranty anyway, and they change it.
      Yes I’d be lucky if i get 1.5 generated…it’s either too hot or too cloudy. I hosed and mopped the panels and this improved a little bit.
      As for the charge it was not automatic but they let me take my chance so I never use them again. So great in the selling phase but after sale forget it!
      I also read another blog where it was said Battery backup is not yet the smart way to go – Price have to go down and Tech improve I think was the essence of it. As one would not get any saving out of it to absorb the initial cost and most likely would need maintenance before it may happen!
      Now I guess it’s arguable that having a system ready for it will still be ok by the time battery becomes a sound option.

  2. Hi Finn , there are a lot of people upgrading their solar systems by just adding AC Solar modules. They don’t have to add a whole string and allows for easy future upgrades. You can also install on various roof faces to match the energy consumption and you do not have to touch the original system, potentially voiding installation warranty. Plus no high voltage DC wiring and associated issues. If they use Enphase Envoy S Metered they can see the consumption monitoring of the entire solar system (old and new) and can simply add the optimum number of Enphase AC batteries once they know exactly how much energy they are exporting.

  3. Ahh.I will correct you here.The Solar rebate does not pay most of the cost.
    To put an extra 4X260watts on your roof will still cost you around $800.00 to $900.00 .I shopped around but I used my original installer and that is what it cost.As for claiming the rebate you can’t claim the rebate.The rebate if any is claimed by the installer and I can assure you the panels are not for free.

    • A 260W Tier 1 panel wholesales for about $200 + GST. STCs are approx $800 per kW installed. So the wholesale cost of the panels is pretty much covered by the STCs.

      Of course the installer must add a margin and installation cost and racking etc (as I point out in the post). But the majority of the cost of the panel hardware is covered by the rebate.

      And you are perfectly entitled to claim the rebate yourself. It is just a lot easier to get the installer to do it for you.

      • Of course but it is on the fitted price of the panels and then the STC,s are applied so it works out roughly at $200.00 per panel but the starting price is in my case on 20 panels was 10,000 plus GST less $4,000 (107 stc’s @38.00) equals $6,000 plus GST cost $6,600.
        The fitting of just 4 panels still requires a road trip of 2 hours and 4 hours fitting for one person plus the profit on the panels and hardware so in my case having 4 panels the starting price would have been $1600.00 (allowing for no inverter) in total less the rebate, so apply that to 20 panels it equals $8,000 plus the cost of the inverter which looks about right give or take $80-90.
        So the retail fitted price is around $400.00 to $500.00 per panel and of course many operators charge much more than that so the cost of 4 panels is still $800.00 and upwards.

  4. G’day Finn,

    I recently heard from a solar installer that, in NSW, the size of the system (for the purposes of the 60c FIT) is gauged by the size of the inverter. Their advice to people faced with the FIT running out was to add more panels, i.e. oversize the array up to 133% as you suggest. According to them, this will not affect the FIT because the inverter size hasn’t changed. They also suggest that the 60c FIT will pay for most of the extra panel cost before it runs out.

    Your thoughts?

    • Hi Andy,

      My understanding is that you cannot add panels to an existing inverter if you are on the 60c scheme and keep getting 60c for all the energy.

      Although the offical guidelines are really badly written:

      What is clear from the FAQ above is that:

      “You must notify your distributor of any change to your Scheme generator that would affect your receipt of Scheme payments. Fines and penalties of up to $110,000 may apply for failure to notify.”

      So my advice is not to just do it and hope the rules are in your favour. I have heard reports of distributors using nearmaps to look for extra panels on roofs and then penalising owners.

      I would call up your distributor and and them if you are OK adding extra panels and not changing your inverter (as the official guidelines are ambiguous). If they say it is OK and you won’t lose your 60c – get it in writing before proceeding.

      Hope That Helps,


      • The official guidelines you have linked clearly indicate that the ‘size’ of the system [vis-a-vis changes to it] is not gauged by the inverter size since you can upsize the inverter [up to 10kW] without affecting the tariff but that the 60c tariff will not be paid on power generated by new panels [vide ‘separately metered’, etc.].

        • Finn Admin says

          How do you separately meter extra panels if they are on the same inverter as the old panels?

          • That’s your problem, not the government’s. The rules say what you may or may not do (in isolation) not necessarily what you can or cannot do together. The fact that the rule on separate metering doesn’t mention separate inverters doesn’t mean you can somehow avoid it – you can’t make assumptions from what the rule doesn’t say.

  5. Hi

    I am going to use one of the three solar installers that you have put forward to me. Thank You.
    I Just want to confirm a few things to make sure that i have read your helpful articles and hints correctly.
    1. We have just been told that we have 3 phase power.( we didn’t realise when we bought our home last September)
    From what you say, It is preferable and more straightforward to just apply solar to the one phase?
    2. We wanted a big system because our electricity bills are around the $1,000 mark with no heating or aircons in the home. The Plumber we used to install a Sanden heat pump for cheaper hot water told us.
    Reading your info regarding oversizing with extra panels, I’m thinking that a 5 kw system inverter (which is the maximum we can install using the single phase) May suffice and instead of the 24 x 260 panels = 6 kw, we have been offered, Maybe we could ask for 25 x 260 panels and this would add up to about 6.5 kw? The maximum to we are allowed to still get and receive our stc’s ? Does that sound right?
    3. We have a very large roof with areas East, West, North and South.
    Would it be wise to put most panels on the North side and some on the West for the late afternoon sun and some on the East side for the early morning sun?
    4. We are on the Sunshine Coast QLD and the Tariffs we have in this house are 33, 31 and peak.
    What is standard tariff ? And should we be on this tariff to use as much solar power before it goes to the grid?
    Apologies if i havn’t understood the info you have supplied correctly.

    Gillian Armstrong

    • Hi Gillian,

      1) Yes – if you are happy with a 5kW maximum inverter, then it is fine to go into a single phase with the solar. A 3 phase inverter would allow you to go bigger.

      2) Yes 6.5kW of panels into a 5kW inverter is a good move.

      3) I would recommend 2kW East, 2kW West and 2.5kW North. A 2 input inverter with the E and W on one input and the N on the other input can work well. Micro inverters would work well too. The E/W and N split will give you a more even spread of power from sunrise to sunset, increasing self consumption of the solar, saving more money.

      4) Tariff 31 is very cheap and can be used to boost your HW overnight very cheaply – so I’d keep it. Depending on your consumption – it may be worth putting everything else that can be run in daytime on the standard tariff so the solar can offset it. But your installer will be able to advise you on this based on what appliances you have.

      Hope That Helps,


    • Tom Roberts says

      Go with Enphase microinverters which give you a truly decentralized, fault-tolerant solar PV system. Central string inverters are an Achilles Heal!!

  6. Hi Guys,

    You cannot claim STCs for addtionnal panels if your inverter is not on CEC list. Most of the old inverters are not on the list anymore because of the change of regulation. !

  7. Hi All, we are looking at putting a second 5kw system on our shed roof. We have a current 5kw system our house which was installed about 4 years ago. We live in Brisbane and receive the feed in tarif rate of I think 45c or there about per kw which was before the axed the higher FIT’s. My question is if we runs a separate system alongside the existing and feed it back into the grid will we still receive the same FIT with double the feed in. Does this present any issues. Thanks.

    • Ronald Brakels says

      Hello Wayne. I’m afraid that any increase in the capacity of your solar system will result in you losing your high feed-in tariff. While you can repair or replace defective components of your old system it’s not permitted to make any change that increases the system’s original capacity. Unfortunately, this includes adding an additional system.

      Update 4 June: Sorry Wayne, what I wrote above was actually wrong. In Queensland it is possible to increase the panel capacity up to one-third larger than the capacity of the inverter and keep the 44 cent feed-in tariff. Unfortunately any change in panel capacity will require the entire system be brought up to current standards which will mean replacing the old inverter with a new one of the same or smaller capacity.

  8. Hi Ronald, thanks for the reply. Do we loose the feed in tariff if we up the existing system to to 133% panels?

    • Ronald Brakels says

      Yes, I’m afraid so. Any increase in capacity will result in the loss of the tariff.

      • How does that work, as the size of the inverter will not be changed only that it will now be putting out the full amount ( hopefully ) that was applied for in the original application to get the tariff .

        • Ronald Brakels says

          Sorry, what I wrote was not correct. In Queensland it is possible to increase the capacity of the panels and keep the 44 cent feed-in tariff provided the capacity of the inverter remains the same. But, unfortunately, any change in the capacity of the solar panels will mean the entire system will need to be brought up to current standards, which will mean the inverter will need to be replaced with a new one of identical or smaller capacity.

          Thanks for pointing out my mistake.

  9. Hi all,
    not sure if this is covered on this blog somewhere, but here goes.

    I’d like to add some extra capacity to my system, but in a strange way maybe.

    We’ve had a Solaredge solarstor 5kw inverter coupled to 19 x 325w LG Neon2 panels for six months now. They are pointing in the most productive direction (just) but I can see that if I had more panels pointing in an easterly direction, that were in some way switched too for use later in the day, my system would generate more KWH each day. Is this even possible?

    Our shed also has ample spare roof capacity which currently unused. It’s a separate building from the main house and has it’s own circuit from the main service box and it’s own breaker unit inside the shed. All the swimming pool equipment. plus some battery powered garden equipment and large wood working tools are powered in the shed. If it had it’s own solar system these cost would never reach my bill. It would also reduce the chance of importing from the network during the day and allow me to choose a smaller battery for evening use when the time comes. (what a shame Tesla stopped making the DC Powerwall2 unit). I’m guessing it would mean (electrically) separating the garage from the house and living with the fact that, on cloudy days I can’t mow the lawn or heat the pool. Living at Tewantin on the Sunshine coast, I think I could live with that 🙂

    Any comments or ideas gratefully received.

    • Ronald Brakels says

      Hello Rob. I believe it is possible to have a set of east facing panels and a set of west facing panels and switch that ensures only one set is ever connected to the inverter at one time. This way you’d never have panels with a total capacity greater than 133% that of the inverter connected to it at any one time, which is the limit. But unfortunately this won’t be cheap as you won’t receive STCs for the extra set of panels and will have to pay their full cost yourself. And of course there is the cost of getting the switch installed.

      Another option is to put the solar panels on a tracker so they follow the sun through the day, but this is not likely to be a practical option.

  10. Arief Abdul Wahab says

    I have been following this site on and off. I do have a question about adding more panels. I had 7.8kW system installed last year (30 panels of Trina Duo Max) and a fronius 8kw inverter (Fronius symo 8.2-3-M). All panels facing North. I enquired to my installer regarding adding more panels but they said because of the way it’s wired (I am not technical, sorry) , it cannot be done without adding another inverter. This was the reply

    “The current way the system is wired is 2 x 9 and 1 x 12 all facing one direction.

    Unfortunately, adding 6 panels to the same inverter will not work with the current wiring.

    The alternative is that we add a Galvo inverter on there with the extra 6 panels”

    I am in Adelaide by the way.

    Please advice.

  11. Arief Abdul Wahab says


    Thanks for the reply and the reference. Indeed both MPPTs are being used for north facing panels 2×9 and 1×12. Would it be better/economical to add another MPPT for upcoming panels on west facing roof? Can add about 10 more panels max….

  12. Finn,
    Our Brisbane residential body corporate committee want reassurance that our Energex approved 15 kWH system approved in 2011 and installed with a Sunny Tripower 150000 inverter can have additional panels to take it up to 133% of the 15KWH ie to say 19 Kwh ? The chairman thought a regulation was bought in in 2016/17 to stop extra panels receiving the STC rebate or eligibility to the 44c FIT we currently receive, but I can’t find any such reference to such a regulation. There is plenty of space available on the north facing flat roof for the extra panels and quoters dont have any issues with the extra panels to install.

    Many thanks

    • Ronald Brakels says

      As far as keeping the 44 cent feed-in tariff is concerned, you can increase the capacity of your solar panel array up to one-third larger than the capacity of the inverter, as long as you don’t increase the capacity of the inverter. But, if you want to add panels, you will be required to bring the entire system up to date. This includes replacing the old inverter with one that meets current standards. This will be a considerable extra expense, but it is possible you will find it worthwhile. As panel capacity can be one-third larger than inverter capacity, with a 15 kilowatt inverter you could have a maximum of 20 kilowatts of panels.

  13. Raymond Simms says

    Hello Finn,
    I have a Fronius IG30 inverter and 7 Sunpower E20 panels installed in 2013.
    Is it worthwhile increasing the number of panels in your opinion, please.
    Thank you

    • Ronald Brakels says

      Hello Raymond, Ronald here.

      The Fronius IG30 inverter has a capacity of 2.65 kilowatts.

      I am not certain what the capacity of SunPower E20 panels were back in 2013, but if they were the same as today, they will be 327 watts each, giving a total of 2.289 kilowatts of solar panels.

      With your inverter you can install a maximum of 3.53 kilowatts of panels, so you could add up to 1.24 kilowatts of additional panels. That would be 3 SunPower E20 panels.

      Because the cost of installing 3 additional panels is likely to be high compared to the amount of electricity they produce, you may want to consider putting the money towards installing a new solar system on your roof in addition to your existing one. (Alternatively, you could remove your existing system and install a large new one, but your old system should still have plenty of years of service left in it.)

      If you are in Queensland you will almost certainly have to replace your old inverter to bring the system up to current standards if you add panels, so it is not likely to be worthwhile there.

  14. David Hince says

    I checked with my original solar installer about upgrading my solar system – currently 6kw panels with 5kw inverter. But they said if I go over 6.6kw of panels then I will lose my 7c Feed In tariff for the whole system (I was thinking of adding another 6kw – preferably as separate system with another inverter) . Whilst the FIT is quite low at 7c, it would definitely make upgrading less attractive. Does that sound right to you, I hadn’t heard of losing the FIT if you add too many panels before? I’m in WA.


  15. john fisher says

    Hello Finn,

    Missing from this article is a fourth method (unless it doesn’t work): Political/Tariff/rebate, etc. questions aside, are there any technical reasons (ie:sparks, loud noises, etc.) that would prevent properly backfeeding 6 or 8 microinverter panels into a remotely located sub panel (in the garage) alongside an existing (far away) “standard” string inverter system at the main house?

    John Fisher

  16. Paul Waiting says


    • Ronald Brakels says


      That’s a good question. The cost of converting to three phase can vary considerably. I’ve seen claims that it can cost as little as $2,000 but I think that can’t include the cost of rewiring the house and with a huge house that may cost a lot. All up it can apparently cost over $5,000 for a typical home and potentially much more if you are not in a good location for it. The first step would be to check who your Distributed Network Service Provider is (it will be on your bill) and see if they have any information about it online. Then you can try contacting them. (Sometimes they take a long time to answer the phone.)

      Merry Christmas!

  17. Bill Ligakis says

    I have a 6kw inverter with 3kw of panels that was on the old tariff system but is now on the new tariff system. I have also got a 4kw system that is 4kw inverter and 4kw panels, that was installed on the new tariff system.

    What i want to know is because i have 10kw of inverters approved and only 7kw of panels can i add more panels up to the 10kw of what the inverters are capable off.( i live in Wagga Wagga NSW)??

    I have also purchased Enphase micro inverters to replace the existing 2 x inverters. Can i just replace the existing inverters or do i need to let the Electricity company i think it is Essential Energy know that i want to do this.?

    I just can’t get a straight answer out of anybody i talk to in the solar game.


    • Ronald Brakels says

      Hello Bill

      What you have planned, replacing the old inverters with Enphase microinverters, should be fine. As long as you don’t exceed the original capacity it’s no different than if your old inverters had broken down and you were replacing them.

      Note the inverter capacity of Enphase microinverters is 10 less than their number. So S230 microinverters are 220 watts and S270 ones are 260 watts. This means you could have up to 43 S230 microinverters and be under 10 kilowatts.

      • Bill Ligakis says

        I have a 6kw inverter with 3kw of panels that was on the old tariff system but is now on the new tariff system. I have also got a 4kw system that is 4kw inverter and 4kw panels, that was installed on the new tariff system.

        What i want to know is because i have 10kw of inverters approved and only 7kw of panels can i add more panels up to the 10kw of what the inverters are capable off.( i live in Wagga Wagga NSW)??

        I have also purchased Enphase micro inverters to replace the existing 2 x inverters. Can i just replace the existing inverters or do i need to let the Electricity company i think it is Essential Energy know that i want to do this.?

        I just can’t get a straight answer out of anybody i talk to in the solar game.


        Hi Ronald,

        So your saying i can add an extra 3kw of panels and then convert them all to micro inverters because i have already been approved for the 10kw because of my 6kw + 4kw inverter.

        Is this correct?


        • Ronald Brakels says

          Hello again Bill.

          I looked up Essential Energy’s page on solar and other micro embedded generation, which can be found here:

          Looking up their Connecting to the Network Information Pack, that can be downloaded from the same page, I see they define a connection alteration as:

          “A connection alteration is an alteration to an existing connection including an addition, upgrade, extension, expansion, augmentation or any other type of change including embedded generation.”

          So it looks like anything you do, including simply replacing an inverter, you “…will need to submit an Application for Low Voltage Connection to be assessed by Essential Energy.”

          To me it seems like they are making work for themselves by covering everything, but those are apparently the rules.

  18. Hi Finn
    I have a 10kw CMS three phase inverter with 3 MPPS outputs which apparently is unusual . currently I have 36 x 185watt panels. which gives me 6.660kw As I understand your information can I hook the 36 panels equalling 6.660 to two outputs and then set up the other output to the south west side of the roof in the form of 14 panels x 260watts equalling 3.620kw, or am I completely out of the ball park re the balance of load on the inverter.

    Cheers Rob

    • Ronald Brakels says

      Hello Rob, Ronald here.

      You wrote MPPS but I am guessing you meant to write MPPT? If you have 3 Multiple Power Point Trackers then this is unusual, but would be very handy for some installations.

      What you have planned sounds good. As long as the panels in each array on each separate MPPT all share the same tilt and orientation it should not be a problem. You should be able to find the inverter’s installation manual online. That will tell you exactly what you can do.

  19. Gavin fisher says

    I would like option no three and a quote for a one kw system with out changing my inverter so I don’t need lose my exiting feed back which is 50 cents a kw thanks Gavin ph 0419400944 .

    • Ronald Brakels says

      I have passed on your comment to Robert and hopefully he’ll be able to help you, but he is away until Monday.

  20. Brenton D McLean says

    Brenton D McLean
    May 9, 16:10 ACST

    I have an old 1kw system installed in 2008 can it be replaced with a new more efficient system without losing my $0.60 feedin rate?

    • Ronald Brakels says

      Hi Brenton

      Generally there is nothing that can be done. I’m guessing you are in South Australia and I’m afraid if you increase the capacity of your household’s solar you will lose the old high feed-in tariff. However, if the panels are failing, you can replace them.

      It is possible you may come out ahead by forgoing your old feed-in tariff and getting a new large solar system installed. Often the easiest way to go about it is to replace the old system and install a single large new one. Here’s an article I wrote on the subject:

      But some people decide it’s easier to just keep their small system and instead help put solar on a relative’s roof.

  21. Lewis Cheung says

    I had a Sharp Inverter installed in 2011 with 7 Solar Panels and I am on 60c feedin tariff. I am thinking of increasing the panels to 133% capacity. Woudl I lose my feedin tariff ? I am in Victoria

    • Ronald Brakels says

      Hi Lewis

      Unfortunately, adding extra panels to your system will cause you to lose your premium feed-in tariff.

  22. Hi,

    I live in Adelaide and have the feed in tariff with a Solar shop SMA Sunny boy 2500 inverter and 25 Kaneka 60Watt thin filmed(1.5KW Installed 2010) on top of the shed roof with enough space for expansion. I have confirmation in writing from SA power the system was originally registered for Total Generation Capacity of 2.9KW. I’m not sure whether the 2.9KW’s refers to the inverters capacity or the amount of panels on the roof. Its my understanding that i can upgrade to the 2.9KW without losing the FiT (is this correct?) and how many additional KW’s of panels can be installed (eg 1.4KW’s taking it up to 2.9KW or taking into account the 133% rule is it different?)

    • Ronald Brakels says

      Hi Sean

      According to my understanding of the rules you can increase your solar panel capacity up to Total Generation Capacity of 2.9 kilowatts. Your current 2.5 kilowatt inverter will be fine for this but it will probably be very difficult to find 60 watt panels to match your current ones. You may need to replace them all which will add to the cost of expanding your system out to 2.9 kilowatts.

  23. John McMahon says

    Hello Finn,
    I have a 3 kw inverter with 2 kw of panels. It was always my intention to add more panels when the subsidy scheme finished. I am now told by installers that panel technology has changed and that I can’t legally install more 185w panels to an ‘on grid’ system and that I need to instead to purchase 3kw of panels. Is this correct?

    • Ronald Brakels says

      Hello John, Ronald here.

      I am afraid that’s likely to be correct as older inverters generally no longer meet current standards. On option is to install a second separate solar system on your roof. For example you could install a 3 kilowatt inverter with up to 4 kilowatts of panels. Another option is to remove your old system and install a completely new system.

      If you are receiving an old high feed in tariff it may not make economic sense for you to change from your current situation.

      • John McMahon says

        Thanks for responding Ronald. As it turned out, the original inverter gave up in 2017 as the NSW subsidy scheme finished and I was changing to a net meter. I now have a new 3 kw inverter, so that part is OK. The problem I’m told is the illegality of adding more 185w panels, which are considered obsolete. Is that correct? It seems wasteful to throw away 2kw of perfectly good panels when I only want to add another 1kw. Also, are 185w panels still available?

        • Ronald Brakels says

          It’s not illegal to add new panels that meet Australian standards but it is going to be incredibly difficult to find new 185 watt panels and old second hand ones may not meet fire safety standards. But if your 3 kilowatt inverter has two Multiple Power Point Trackers (MPPTs) then it can have two separate strings of panels. It may be possible to put your 185w panels onto one string and new higher wattage panels onto the second string. If your inverter only has one MPPT then I suppose adding new panels with optimisers would be an option. If you only want one additional kilowatt of panel capacity you could add 3 large new panels with microinverters but that is not a cheap option.

  24. Hi,

    I will be having a 1.7kw Solar Roof Tile Suntech BIPV with a Fronius Symo inverter (unsure which one is included, anyone knows what the fit is)

    I want to use Option 3 and add 5-6Kw to North roof line with no shading.
    but I’m unsure whether the difference in cost to install LG Panels with Enphase S270 or IQ7 Micro Inverters versus Cost saving of a similar String system?

    Does using the Enphase configuration blow out the ROI?

    I’m in Sydney on Endeavour Energy with flat rate Peak and Controlled Load 1 for pool pump.

    Also keen to understand how the 3phase smart meter manages the Feed in across 3 phases?

    Ie: If the Solar Feed-in is pushed into phase A and and generates say 20Kw surplus (feed-in) and Phase B uses 10Kw, does the smart meter simply pay me the 10Kw surplus? Or; as it is on the different phase do they pay you 20Kw feed-in rate and charge you the 10Kw usage on phase B?


    • Ronald Brakels says

      Hello GLO, Ronald here.

      LG panels are high quality and now have a 25 year product warranty, but you will have to pay a premium for them. If you are looking for a rapid return on investment then a string system would be the way to go. Microinverters have some advantages you may consider worthwhile, but if your main interest is an economic return and you have an unshaded roof then a string system will have a lower up front cost for almost identical output.

      A three phase export meter just looks at the net amount of power going into or leaving a home. So if the home is importing 2 kilowatts on two phases and exporting 5 kilowatts on the other phase the electricity meter will regard the home as exporting one kilowatt at that time. If that goes on for an hour the household will receive one kilowatt-hour of feed-in tariff.

      • Hi Ronald,

        Thanks for your reply,.

        I will stay in this new home build for the duration of the LG Warranty!

        The other things i have in mind is adding more panels in coming years.
        Part of build: 1..7Kw BIPV (West Aspect)
        Stage 2: 5-6kw (17-18) PV panels (likely to be Enphase Micro Inverters) (North aspect 2nd storey)
        Stage 3: 1.8Kw (6 panel 2nd storey) Enphase
        Stage 4: 2kw East + 2Kw West (on pitched gabled Pergola roof) note that East facing roof space would receive morning sun year round, however the West facing pergola roof would be shaded and ineffective in Winter due to the winter silouette of the 2storey house.

        Elaborating on the 3pjhase smart meter. As the Pool is on the Controlled Load 1 line, effectively the 4th phase or separate meter, Then that would mean that I would collect Net Feedin credit on then 3main phases, but would incur the Controlled Load 1 phase usage for the pool. Thus not totally offset.

        Am i losing any benefit by having the pool on the controlled load 1 (T31 i think) and receiving the credit on the main 3 phases? Or is there a way to toggle the pool onto the main line in Summer when there is surplus usage?

        • Ronald Brakels says

          You will have a choice between leaving the pool on a controlled load or putting it on a timer so it turns on during the day. If you will soon have over 6 kilowatts of solar panels then you are probably better off putting it on a timer but it will depend on the difference between what your feed-in tariff is and what you pay for controlled load electricity. If your feed-in tariff is high enough it is possible, though unlikely, that putting your pool filter on a timer won’t be worthwhile.

  25. Daniel Debreceny says

    I have recently installed a Solaredge Storedge SE6000 inverter (DC Battery Ready / non-HDWave) with 24x LG 320W panels complete with DC Optimisers .

    I am considering getting a LG RESU10H battery (9.3kWh / 5kWp), and Solaredge have updated their warranty for the SEx000 series to allow for Solar Panel over-sizing of upto 5kWp when used in conjunction with a DC coupled battery.

    If I add a battery and add additional 3.32kW of panels with DC Optimisers at the same time, can I claim the STCs for the upgrade to the solar system?

  26. Ron Murray says

    Hey Ron this is Ron Murray from Crystal Creek NSW
    I have a 5 kw system 30 panels 10 on each array feeding into 3 separate inverters . 2 of my inverters pooped themselves & I purchased today a 5 star second hand 5 kw inverter for $200
    It only has two dc input plugs (+& -) twice . Can I join two dc outputs together in parallel to fit one plug or install a third plug if internally they connect together regards Ron

    • Ronald Brakels says

      The manufacturer’s guidelines will need to be followed and these vary from inverter to inverter. The inverter has 2 MPPTs or Multiple Power Point Trackers and it is likely but not certain you can connect 10 panels to one MPPT and then arrange the two remaining currently separate strings so those 20 panels can be attached to the other MPPT. If you are on-grid a second hand inverter will need to meet current standards and you’ll need a qualified installer.

  27. Hi Finn,
    I would appreciate your answers to the following questions. I each, I include the relevant quote from your article.

    1. “And if you don’t go over the 133%, you can claim the solar rebate (STCs) on those extra panels which will cover a big chunk of their of their cost (excluding installation costs and installer margin).”

    I cannot understand what you mean by that. Because if you don’t go over 133%, then it is the end of the matter. There is nothing to do or claim. Unless of course you meant, you still go over but by less than 133% such as 100% or 80% or whatever.

    2. “with panel technology changing so quickly, you may struggle to find extra panels that match your existing array. In this case get an inverter with 2 or more inputs so you can install new, different panels without affecting the old array.”

    Are you referring to the number of MPPTs or to number of strings within a MPPT? I just double checked Fronius Symo 10.0-3-M for example, its technical data say it has 2 MPPTs and 3+3 as the number of DC connections. Please clarify. So, where is the limitation applicable in terms of mixing different panels models or technologies?

    3. “If possible get the original company to do the work, then they keep the responsibility for the system warranty.”

    So, one would have to assume that if the original company is no longer there, then any company can be contacted.

    4. “…the word on the street is that in practice it is only usable in their expensive ‘hybrid’ models. Perhaps some one from Fronius would like to comment?

    Has that been clarified since the time of your article?

    Many thanks

    • Ronald Brakels says

      Hello Mahmoud, Ronald here.

      1. If a household was going to install a 5 kilowatt inverter with 5 kilowatts of solar panels then it would make sense, provided they had room on their roof, to increase the panel capacity as close to the maximum that’s allowed which is 6.66 kilowatts. Outside of Western Australia it is generally possible to go over this by export limiting the system and which is easier to do now than when this article was written.

      2. This is referring to MPPTs. These days basically all but the smallest residential inverters have 2 MPPTs which allows for two sets of panels that face different directions.

      3. Installers generally don’t like touching other installers work, but if the original installer is no longer around then there is no choice but to hire someone else. Of course looking around for someone else because what the original installer wants to charge is a little steep is also reasonable.

      4. These days only hybrid inverters can practically be used to interface with DC coupled batteries and manufacturers will state which battery systems they are compatible with. But I recommend checking online to find examples of batteries being installed with that inverter to make sure they really are compatible in practice. More reputable brands of inverters are less likely to exaggerate compatibility, but I still recommend checking.

  28. hi have a brand new 1-5 inverter sitting in the cupboard so can I sit beside my existing one and add panels so that I have 2 systems working together, John.

  29. paul Lapere says


    • Ronald Brakels says

      Hello Paul

      In South Australia the solar panel capacity you can have and still receive the high feed-in tariff depends on the capacity given in your ‘permission to connect’ notice from SA Power Networks. If it says you can install 2 kilowatts of panels then you can install panel capacity equal to 133% of your inverter capacity or as close to it as you can get without affecting your feed-in tariff. It’s even possible you were given permission to install more than 2 kilowatts of panels. But if you were only given permission to install 1.5 kilowatts of panels you won’t be able to install any more without losing your high feed-in tariff.

      If you can’t find the original documentation you can check with SA Power Networks. I also recommend checking with them if you are making any changes just to be sure there won’t be any problems with your feed-in tariff.

  30. Isaac Witton says

    Hi Ronald

    I currently have a 3kw north facing system, with an old xantrax inverter, this was installed about 3-4yrs ago. I am currently exporting about 7kw a day and importing about 5kw. I have maxed out my north facing roof, so I am looking to install a new 3.6kw system split into two on the west and east sides, to try and export enough to cover out existing bill.

    Would it be best to install a completely new system with a string inverter or go with micro inverters. There are not shading issues.

    Also if I went for a new system, what would be the best inverter to go with if I wanted to add batteries in the future.

    I am in South Australia.

    Thanks mate


    • Ronald Brakels says

      Hi Isaac

      Without shading microinverters may only result in 1-2% more output over a string inverter, mainly because they reduce the effects of dirt and bird poop.

      Because you are in South Australia and can get the up to $6,000 battery subsidy it is possible a batteries will be able to save you money now if your overnight electricity consumption is high enough. Here’s an article to help you work out if they are worth it:

      If a battery will save you money and then you can pick one out and get an inverter that suits it. If you don’t want to get a battery yet then if you pay extra for a hybrid inverter it may not turn out to be compatible with the battery you end up wanting to get so you may be batter off saving money by not getting a hybrid inverter. Then you can either replace it in the future or get an AC coupled battery that will function with a standard inverter.

      But whatever you decide you may want to consider using export limiting to get install a new solar system that is over 3.6 kilowatts to ensure your battery will be able to fully charge in winter and on cloudy days. Replacing your old system and putting in a large new system is also an option and it is possible for that to make economic sense although it is a pity to remove a working system if it’s decent quality.

      ThiYou may want to get a battery installed at the same time as your new system. If you want to wait to get a battery then there isn’t a lot of point choosing a particular inverter as

  31. Howdy,
    Six months ago I added 2 panels to an 8 panel (1.5kw) system that was about 8 years old and was going great until a couple of weeks ago. Initially I thought it was the inverter (fault light) and so replaced with secondhand inverter (SMA). This gave a DC overvoltage error – after further investigation and numerous trips up the ladder I have found that it will run happily with either of the added panels (total 9) but not both. While connecting and disconnecting cables I also found an earth wire to rail was a bit loose and a cable join from -ve or +ve wasn’t properly insulated and repaired. Neither of these actions allowed me to run all 10 panels again as it had been doing for the last six relatively warm and dry months. Can you offer any suggestions on what is occurring?
    Thanks in advance.

  32. Is it possible to provide an update on this topic of adding to an existing system. With newer hybrid inverters available, would that be a more updated option. Given most inverters only have 2 string inputs, whats the current best way to add a third string direction?

    • Ronald Brakels says

      Generally you will be better off getting a second new, separate system than adding to an existing system. It’s normally cheaper and installers frequently don’t like touching other installers work, so it will be a lot easier to find someone to do it.

      If you do want to add a third array direction, some flexible inverters such as Fronius can, under the right circumstances, handle 3 array directions, otherwise the third array will need optimisers or built in Maxim optimization.

  33. Xavier Robinsonn says

    Hi Ronald I have 6.6kw of Longhi panels with a fronius 5kw inverter on single phase . fantastic system up to 50kw a day peak summer in Melb . i want to add another system do i need another meter ? or 3 phase an m i best to use micro inverters this time ? I would like to keep it to $6000

    • Ronald Brakels says

      Hi Xavier

      If you have three phase power the cheapest option is likely to be install another single phase inverter and put that on a different phase to your other inverter. You could replace you existing inverter with one large 3 phase inverter, but this would add to the cost.

      If you don’t have single phase power and you are not in one of the few areas that still allow 10 kilowatts of inverter capacity with single phase then you will probably have to export limit the new solar capacity.

  34. Hi Ronal I’m Lee in Melbourne , I have 3 kw solars system on the roof ,can I add more Panels by my self just only one more kw my inverter 4kw Thanks

    • Ronald Brakels says

      Hi Lee

      It is possible to add one more kilowatt of panels to bring your system up to 4 kilowatts. This will have to be done by an accredited solar installer. It also likely to be expensive for just one extra kilowatt of solar panels. If you want more solar you may want to consider if it is worthwhile to remove your old system entirely and put a new large system in its place.

      Another possibility, if your roof is large enough, is to leave your current system as it is and add a second new system, but you still might be better off getting one large new one.

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