Should you scrap your 1.5kW solar and replace it with a bigger system?

solar rag and bone man

Should you bite the bullet and scrap your 1.5kW solar system so you can fit a bigger system on your roof?

Five to eight years ago, just as the Australian solar industry was getting underway, many people locked in high feed in tariffs for their new, cutting-edge solar power systems.  For example, many people in Victoria with systems installed before 2012 are now getting 71.3 cents per kilowatt-hour of solar electricity exported into the grid.  And they will continue to receive this for almost 7 more years.

While these sky high feed-in tariffs sound wonderful — and trust me, they are wonderful — most people who locked in dreamy feed-in tariffs only had very small solar systems, with the most common size being 1.5 kilowatts.  This is because back then, not only were solar power systems incredibly expensive, but subsides were greater for smaller systems.

Having a high feed-in tariff  isn’t necessarily the golden goose it might seem for owners of small systems who don’t export much of their solar electricity. It’s more a golden willy wagtail or in Queensland perhaps a golden gecko.

Golden Geko

If you google “Golden Gecko” this is the first image that comes up. While it looks like Queensland, something isn’t quite right. The geckos look a little too happy.

As a result, many of the owners of these old PV systems are in a quandary: should they scrap their small 1.5 kilowatt system, along with the high feed-in tariff and replace it with a larger system that generates more electricity?

Should you replace your 1.5kW with a larger system?

The answer to that question can be clearly given in just two words — it depends.

In Victoria the premium feed-in tariff is so high you probably won’t come out ahead.

In the ACT a high feed-in tariff combined with Australia’s lowest electricity prices makes it a bad idea.

In Perth the feed-in tariff the new system will get is so low you’re also unlikely to come out ahead.

But in Tasmania, Queensland, and South Australia, it can save you money, provided your cost of capital isn’t too high.

While 1.5 kilowatts is the most common size that gets a high feed-in tariff, some people did buy larger systems, with the limit generally being 5 kilowatts.  So if you’re receiving a 71.3 cent feed-in tariff for a 5 kilowatt solar power system, this article is not for you.  You should be raking in that feed-in tariff money.  In fact, if you are single, send me your phone number1.

Existing High Feed-In Tariffs And Their End Dates

If you have locked in a high feed-in tariff for your solar system then you probably know about it.  If there is any doubt, you can check your electricity bill to see if you get a fat payment for every kilowatt-hour you send into the grid.  It is possible you may not know when your high feed-in tariff will end, so here’s a list of all the remaining old-time high feed-in tariffs and when they expire:

  • Victoria:  A minimum of 60 cents a kilowatt-hour with a retail feed-in tariff of at least 11.3 cents on top of this, making for a minimum feed-in tariff of 71.3 cents.  Ends in late 2024.
  • The ACT:  Rooftop solar applied for before the 13th of July 2011 could lock in a feed-in tariff which is now a straight 45 cents.  It can last for 20 years, so some households will still be receiving this in 2031.
  • Western Australia:  Those who applied for rooftop solar from the 1st of July 2010 till the 30th of June 2011 could lock-in a 40 cent feed-in tariff for 10 years and those who applied in July 2011 could lock-in 20 cents for 10 years.  This will end from 2020 to 2021.
  • Tasmania:  Those who applied to install solar before the end of August 2013 received a feed-in tariff equal to the retail cost of electricity.  But this ends at the start of 2019 so there’s only one year left to go.
  • South Australia:  Applying to install solar panels before the 30th of September 2011 would lock-in a a 44 cent distributor feed-in tariff until the 30th of June 2028.  The retail feed-in tariff is received on top of this, so a household with a 17 cent retailer tariff would receive a total of 61 cents for every kilowatt-hour of solar electricity exported.
  • Queensland:  Those who applied to install rooftop solar the 10th of July 2012 received a straight 44 cent feed-in tariff which will last until the 1st of July 2028.

NSW used to have a generous feed-in tariff, but that came to an end last year.

While it is permitted to replace components that fail, it’s usually not possible to increase the capacity of a system or add a second solar system without losing the feed-in tariff.  In Queensland, while the inverter size can’t be increased, it is possible to increase the panel capacity up to a maximum of one-third more than the inverter capacity, but only if your inverter meets modern standards.

There are still high feed-in tariffs available in two places in Australia and they are the Northern Territory where the feed-in tariff is equal to the retail price of electricity and some parts of rural Western Australia.  The drawback of the high feed-in tariffs in rural WA are it can be impossible to receive permission to install solar panels.  But if you can get solar in these places, it’s a good idea to install as much as you can.

Old Versus New Comparison

Most homes in Australia have single phase power and the maximum amount of solar panel capacity they can usually install without paying extra for export limiting is 6.66 kilowatts.  Homes with three phase power that aren’t in Western Australia can install more solar provided they can fit it on their roofs, but I will limit myself to comparing the annual savings from keeping a 1.5 kilowatt system with a high feed-in tariff with the annual savings from replacing it with a 6.5 kilowatt system.

Replacing Versus Expanding

If you decide to give up your old feed-in tariff and expand your solar energy capacity, you have a choice between:

  1. Removing the old system and replacing it with a new one.
  2. Keeping the old system in place and installing a separate new system.
  3. Attaching the old panels to a new inverter so they become part of a new system.

While it may seem that keeping the old system or making use of the old solar panels would be the cheaper option, this often isn’t the case.  The larger a new solar system is, the cheaper it will be per watt and it gives the advantage that the entire system, including the panels and inverter, will be covered by new warranties.  This can avoid the need to make expense repairs to the old system, as if you have locked in a high feed-in tariff then your inverter is almost certainly out of warranty and could potentially die at any time.

Furthermore, any system old enough to get a high feed-in-tariff will be almost certainly be using solar panels and inverters that are not compliant with the latest Australian Standards. If you upgrade it, the whole installation will need to comply with the current standards. For most people this will require a new inverter and panels, essentially a whole new system.

Finally, most local networks (DNSPs) only allow 5kW of inverters on a typical, single phase home.

So I will assume the old system will be removed and completely replaced with a new one.

Household Solar Energy Self Consumption

How much of a solar power system’s electricity is consumed by the home it is bolted to will affect the amount of money it saves over a year.  Personally, I always talk about the self consumption rate of households, but just to make things a little confusing, this graph from the Australian Energy Council’s Solar Report December 2016 turns that upside down and shows the export rate of households for different sizes of solar systems.  But don’t worry, it’s only a little confusing.  I’m sure you can work it out:

Generally, the smaller the system the higher the self consumption rate and according to the graph, a household with a 1.5 kilowatt system will self consume around two-thirds of the electricity it produces.  I realize that two-thirds isn’t quite the same as the 63% self consumption rate on the graph, but I’ll use 66.6% because it’s easier to work with a nice round fraction and not at all because that is the number the voices scream at me from the bottomless pits that have been torn in my mind2.

But people who are out of the house for most of the day may have a self consumption rate of only around one-third.  So I will also estimate savings for homes with one-third self consumption, as this can considerably increase the amount of money saved.

However, if you are one of these people who does things like turn your refrigerator off during the day to try to get your solar electricity self consumption down to zero and maximize your feed-in tariff money, then I’d suggest that maybe you are taking things a little too far and you should probably get another hobby3.

According to the above graph a home with a 5 kilowatt solar system will typically self consume around 26% of the solar electricity generated.  But since I’ll be using a 6.5 kilowatt system for comparison, which is off the graph, I’ll estimate self consumption to be 20% for a typical household and 10% for one where there is usually no one at home during the day.

Estimating Annual System Output

The United States has given the world some amazing things.  For example, they gave us the space program that put humanity on the moon and the conspiracy theory that says they didn’t.

One very useful thing they have gifted to us is the PVWatts site that can estimate the output of solar systems around the world.  Sure, you have to be careful to tell it “Melbourne Australia” and “Darwin Australia”, otherwise it will take you to towns with those names in the US4, but apart from that peccadilo5 it’s really quite handy.

PVWatts says a 1.5 kilowatt system in Melbourne that faces north and is tilted at a 20 degree angle will produce 2,058 kilowatt-hours a year.  But that figure is a little optimistic.  Solar panels slowly degrade over time and older systems with high feed-in tariffs are also likely to have inverters that are a little less efficient than modern ones.  Also, not every system is faces directly north.  To allow for this I will reduce the figure PVWatts gives by 10% and assume it will produce 1,852 kilowatt-hours a year.

PVWatts says a 6.5 kilowatt system that faces north at an angle of 20 degrees will produce 8,918 kilowatt-hours over a year.  But while these panels will be newer and inverter is likely to be more efficient, because of the large size of the system it’s going to be harder to optimally position all the panels and to account for this I will reduce their output by the same 10% amount.  This means I’ll expect it to produce 8,026 kilowatt-hours a year.

Savings From A Melbourne High Feed-In Tariff 1.5 KW System

Using the SolarQuotes retail electricity plan comparison tool I see that while electricity prices in Melbourne are considerably higher than what they were a year ago, by Australian standards they are actually pretty good6 and, after discounts, the most cost effective plan I can see charges 18.3 cents per kilowatt-hour of grid electricity and has a feed-in tariff of 11.3 cents.  Adding this onto the base 60 cents of Victoria’s old premium feed-in tariff gives a total of 71.3 cents.

With a self consumption rate of 66.6% the 1.5 kilowatt system will save a household $666.60 a year7 on electricity bills.  If the self consumption rate is only 33% then the high feed-in tariff causes the savings to jump to $994.

Savings From A New Melbourne 6.5 Kilowatt System

After crunching the numbers I find that a 6.5 kilowatt system with the current 11.3 cent feed-in tariff and a 20% self consumption rate will save a Melbourne household $1,020 a year.  If the self consumption rate is only 10% then it will save $963.

But while this makes a new system appear worthwhile, it unfortunately ignores the cost of capital.  This is important to take into consideration because it is very unlikely that a brand new 6.5 kilowatt solar power system will fall off the back of a truck, bounce off the road, and land fully installed on your roof.  The only realistic way you are going to get one is to pay an installer to put it there.  So I will assume the system will be completely replaced and the total cost of the new system and disposing of the old one will come to $8,000.

Estimating The Capital Cost Of A New System

To work out the yearly savings from a new solar power system it is necessary to estimate what the cost of capital over a year will be.  I am going to use a very simple method.  Some people might say it is too simple, but fortunately, through a stroke of sheer luck, I don’t care.

I am simply going to say that people who don’t really have anything better to do with their money other than put it in the bank or make a house payment have a cost of capital of 5% and simply deduct 5% of the $8,000 cost of a new system from its yearly savings.  I am not going to worry about anything else and simply  assume the new system will fully pay for itself after the high feed-in tariff ends, which will be within 10 years everywhere except the ACT.

Some people have a higher cost of capital.  These are either people who don’t have home equity or other cheap way of borrowing money, or who make a decent return from the money they do have such as by investing it in their own business or the share market.  I will assume these people have a cost of capital of 8% and deduct 8% of the $8,000 cost of a new system from their yearly savings.

It is quite possible for people’s cost of capital to be over 8% but if this is you, I can tell you now you probably aren’t going to be better off replacing a high feed-in tariff solar system.  Instead, cut up your credit cards, pay off the Dutch mafia, or do whatever else you need to get your finances in order and then look at replacing your old system.

Graph Of Potential Savings For Melbourne

If we take the yearly savings that are possible with the different self consumption rates and cost of capital for Melbourne and then put them in a graph we get this:


As you can see, while it is close for people who currently have typical self consumption and a low cost of capital, Melbournites aren’t likely to come out ahead economically.  And for people who currently have a low self consumption rate, Victoria’s massive premium solar feed-in tariff means these households are way ahead if they keep their old systems.

Using the same method, I will now make graphs for every capital where it’s possible to have a locked-in high feed-in tariff.  I’ll continue in the order I have started, from worst to best.



While the straight 45 cent feed-in tariff isn’t the highest, Canberra does have the lowed grid electricity prices in Australia and so scrapping an old system is not likely to pay for itself.  The low cost of electricity makes it an especially bad idea if you have a high cost of capital.

(I have changed this graph from how I originally had it because I used the wrong information for the ACTs old premium tariff.  Thanks to Tony for pointing this out in the comments.  I hope the information I have now is correct.)

Graph For Perth


Because Western Australia’ current feed-in tariff is the lowest in Australia, getting a new system isn’t likely to pay for itself.  But this could all change if Western Australia increases its feed-in tariff, at which point I suggest we all hop on flying pigs and ride them to Fremantle for a party.



Hobart is the worst city in Australia for sunshine.  But, with a low cost of capital, it can be worthwhile to replace an old solar system and lose a high feed-in tariff.  Tasmania’s premium is ending in one year anyway, so it’s definitely not too soon to start saving for a larger PV system whether or not it’s worth losing a high feed-in tariff now.


Under the right conditions it can be worthwhile for people in Queensland to ditch their 1.5 kilowatt systems and install something larger.  And grid operators there will love you if you do, since they keep complaining about high feed-in tariff households waiting until the evening to use electricity, which makes it harder to meet peak demand.

But the figures for Queensland could actually be a lot better than the graph suggests as, starting next year, Queenslanders may be able to get interest free loans for solar.  Details of how this will work don’t appear to be online yet, so I didn’t include it in the graph, but if you can get 6.5 kilowatt system interest free then it definitely makes sense to replace a 1.5 kilowatt system with a high feed-in tariff, but if it’s over 2 kilowatts you’ll want to think about it.  Unfortunately, some of the language used by the state government makes me think these interest free loans will not be made available to everyone.




Adelaide is the best capital in Australia for scrapping a high feed-in tariff and if your cost of capital is low the savings can be bloody good.  Even if your cost of capital is high and your self consumption low you should come close to breaking even.  So if you are in Adelaide and have money in the bank, scrap that puny 1.5 kilowatt solar power system and get yourself something decent.

What About Systems Smaller Or Larger Than 1.5 Kilowatts?

If you have a system that is only 1 kilowatt then the savings it provides will be around two-thirds of what’s shown in the graphs above.  This means it will often be worthwhile to replace it.  Savings from a 2 kilowatt system will be about one quarter more than in the graphs and so it will generally make sense to hang onto it.  Unless you can get a zero interest loan or something.

Current Feed-In Tariffs May Change

It is definitely possible feed-in tariffs will fall in the future and so increase the value of hanging onto a locked-in high feed-in tariff.  But I am very confident the cost of rooftop solar energy will continue to decline, despite the gradual phasing out of the “solar rebate8“, and that may offset any decrease in feed-in tariffs.

My Solar Power System Died!

The older a system gets the more likely it is that something will fail and require expensive repairs.  This is most likely to be the inverter if it hasn’t already been replaced, but solar panels and even wiring can die in a variety of different ways.

It is likely to cost around $1,000 to replace a 1.5 kilowatt inverter.  If you get a high quality inverter it will cost more, but in this particular situation a high quality inverter may not be a good choice, as even a cheap one is likely to last until your high feed-in tariff ends and even if it dies as soon as its 5 year warranty is over, by that time there is an excellent chance by that time rooftop solar will have fallen enough in price to make it worthwhile to simply install a larger system.

If your old solar energy system of around 1.5 kilowatts need repairs it may make sense to pay for them in Victoria, Queensland, and the ACT, particularly if you have a high cost of capital.  It’s possible it will be worthwhile in Perth, despite its high feed-in tariff ending within 3 years, but its very unlikely to pay for itself in Adelaide and sure as hell won’t pay for itself in Tasmania where the high feed-in tariff is ending in one year.

Save The Planet!

I have only discussed the economics of replacing a small solar power system with a high feed-in tariff.  If you want to help the environment then you could definitely find it worthwhile to install a larger system.  But if you are getting a pretty sweet deal from a high feed-in tariff, I will mention you can help the environment by installing a system on the roof of a relative or by donating one to charity.  You could also invest in energy efficiency measures in your home that will both reduce emissions and increase the amount of solar energy you send into the grid.


  1. I’d prefer it if you are female, but I guess beggars can’t be choosers.
  2. For one thing, there’s no decimal point in the number they scream.
  3. But if you are doing this because you are poverty stricken, then it could be a smart move.
  4. Actually, I’m surprised they haven’t renamed American Darwin as Creation Town USA.
  5. Spanish for “small pecker”.
  6. But they will rise by around 10% in a few weeks time.
  7. Odd, the constant screaming from the bottomless pits torn in my mind seems to be reaching a crescendo for some reason.
  8. Not actually a rebate.
About Ronald Brakels

Joining SolarQuotes in 2015, Ronald has a knack for reading those tediously long documents put out by solar manufacturers and translating their contents into something consumers might find interesting. Master of heavily researched deep-dive blog posts, his relentless consumer advocacy has ruffled more than a few manufacturer's feathers over the years. Read Ronald's full bio.


  1. Hi Ronald,
    Here in NSW one Energy retailer Enova a has a deal for people who cannot fit either more panels or as renters any panels. If you use Enova as a supplier you can invest money with them to put panels on business roofs. The business gets cheaper electricity and the investor gets a deduction on their electricity bill some estimates give this a 10% return on capital. Sounds interesting.

  2. In Canberra there is also a legacy government program (50.05 cent per kWh rebate for 20 years) if you installed before, I think, 2010. They permit additional installations as long as they’re maintained totally separate from the original installation.
    Not sure if/how that might affect Canberra calculations?

    • Ronald Brakels says

      Just ringing ActewAGL to check the tariff. On hold…

      Still on hold…

      Okay, don’t think I’ll eat this week with what this call is going to cost me…

      Finally! Someone who can’t help me!

      And they’ve put me on hold…

      Okay, they’ve told me the old premium tariff some people are receiving is 45 cents. Unfortunately they don’t know much else, but I will update the article.

      Thank you for pointing this out.

  3. Ronald,
    In NSW (with time-of-use metering), how about retaining an existing 3kW, North-facing panel system on two 1.5kW inverters, but moving the panels to East-West facing; purchasing a 5kW system and installing North-facing panels; and making the “old” 3kW system zero feed-in?

    Especially if you had access to a couple of “spare” 1.5kW inverters that were only a couple of years old that had been installed inside a garage, wouldn’t this have the benefit of eking out the life/value of the original system at minimal cost, plus maximise the self-consumption component of usage (I’m home during the day), as well as maximising the export component of the new system?

    Also, in your article you mention the potential of donating your old system to a relative or charity. I seem to recall you stated in an earlier article that the purchase of a second-hand system was ill-advised and that in many instances the second-hand system could not be legally installed because of the change of standards that have evolved over the longer term?

    Thoughts, please?

    • Ronald Brakels says

      Hello Greg

      There are no longer any premium tariffs to lose in NSW, so that’s one thing you don’t have to worry about.

      Buying a new 5 kilowatt system and moving two 1.5 kilowatt arrays is an option, but I would definitely suggest looking at how much a new 8 kilowatt system will cost you instead. With a conventional inverter you’ll only be able to have two arrays facing two different directions, but relocating the two small arrays is likely to be a considerable expense. (Of course, just getting rid of them will also be a cost.)

      If you have single phase power and you get a new 5 kilowatt system, then exporting the two 1.5 kilowatt systems will hopefully satisfy your Distributed Network Service Provider and be permitted. However, the cost of export limiting those two 1.5 kilowatt inverters might be expensive. It might be easier to export the new limit to 2 kilowatts instead.

      With regard to donating a system to charity, I actually meant a new one. Clearly, this is only an option for people with money. But it may be possible to donate used panels for use overseas. This is something I should probably look into and write about.

    • Hi Greg,
      I don’t think Ron was suggesting giving your old system away. I understood it as buying a new system for a relative or charity out of concern for them or the environment BUT only if you are making a motza from your existing system and you can’t change anything without losing the high feed-in tariff.

    • Hi Greg,
      I asked two different companies if I could move my old 1.5Kw system from north facing so I could put a new system there and the old to facing east. Both said the inverter and panels no longer met the new standards so no go.
      Great minds think alike.

  4. “However, if you are one of these people who does things like turn your refrigerator off during the day to try to get your solar electricity self consumption down to zero and maximize your feed-in tariff money, then I’d suggest that maybe you are taking things a little too far and you should probably get another hobby”
    Guilty! Although with fuzzy logic in refrigerators the fridge runs longer after an outage so I gave that tactic a thumbs down.
    However I do load shift the washing machine and ebike charging to the evening. It is a sickness, I know. I’ve even considered a separate off grid system so I can export more.

  5. Hi there Young Fella.
    Very well put-together article. Just one small point:-
    “If you google “Golden Gecko” this is the first image that comes up. While it looks like Queensland, something isn’t quite right. The geckos look a little too happy.” —>
    ….and intelligent.

  6. I am wondering whether, if people are getting rid of 1.5kW systems, a marketplace exists for buying/selling 250W panels.

    I have not been able to find any company that sells them new. I want to expand what we have, which is all 250W polycrystalline panels, but they are now apparently unobtainable.

    • Ronald Brakels says

      Hello Brett

      Yes, 250 watt panels do seem to have disappeared. I am sure someone will still be selling new ones, as they are extremely common, but I couldn’t see anyone with just a quick look. Second hand solar panels are an option. Of course, second hand solar has some disadvantages:

      You can install higher capacity panels, but their performance will be dragged down to that of the worst performing panel on the string.

  7. You say “NSW used to have a generous feed-in tariff, but that came to an end last year” You didn’t complete the sentence. You missed off the words “and so domestic PV installations in NSW cannot be justified on cost savings.”

    A typical feed in tariff (eg from Origin) in NSW is 9 cents. A few are higher – up to 12 cents – but typically those plans have nasty usage rates and nasty daily fees.

    A typical 6.5kWh system costs $8,000 (using your figures).

    – At 9 cents per kWh and a zero cost of capital, that means the system needs to generate 88,888 kWh to pay for itself

    – At 9 cents per kWh and a 5% cost of capital, that means the system needs to generate an extra 5% to pay for itself. That is 93,333 kWh

    Your estimate for Melbourne is that a 6.5 kWh system will generate 8,026 kWh per year. Assume the same system in Sydney generates 10% more (a heroic assumption). It’s still going to take 11 years for the savings from the Sydney system to pay for the outlay ie 11 years before you actually save a single dollar! Good luck in finding a system that will not cost you a penny in maintenance over eleven years.

    AND that eleven year payback for NSW is all predicated on your system generating the 93,333 kWh. Maybe your roof does not face north. Maybe the panels are not at the ideal 20 degrees elevation. Maybe there is some shadow from local trees or buildings.
    Maybe you will get nowhere near 8,026 kWh per annum from your system.

    Maybe you will be better spending your $8,000 on extra roof insulation or wall insulation, or heavy curtains or exterior blinds.

    AND one last consideration – valid for all sites, not just NSW. Before you spend $8,000, take a good look at your roof and convince yourself it is going to last ten years without work. If you think that there is a chance that in that time you will need to replace tiles or rusted out corrugated iron then you need to do that before you start. Otherwise your PV system will become worthless – it will not be economic to take it off, fix the roof then pay for re-installation (And in this, I speak from bitter experience)

    • Pensioner,
      I think there is a major flaw in your figures – only taking into account the FIT and disregarding the savings of self-consumption of the PV production.

      Assuming a 6.6kW system:
      Producing an annual average of 30kWh per day;
      Total day-time consumption for the household of 10kWh p/d;
      Feed-in to the grid of 20kWh p/d;
      Saving $3 p/d in Peak electricity charges (at, say, 30c/kWh on ToU tariff);
      Attracting $2 p/d FIT (at 10c p/kWh – with 12.8c to 16c/kWh rates available);
      Equating to a saving of $1,825 per year;
      Indicating a payback period of under four-and-a-half years.

      Obviously there would be “swings and roundabouts” with the above figures, varying from customer to customer (based on location, efficiency of system, usage patterns, etc, etc, but the sub-four-and-a-half year payback figure is definitely do-able.

      But commiserations on your roof issues.

      • Exactly, the self consumption is where the savings are at. Summer weather and reverse cycle air con is where solar cleans up big time. You might use 25kwh cooling your house on a hot day but the sun is out, the 6.6kw system is going to make upwards of 40kwh on sunny days (mine does).

        Here in SA it is saving me $700-1000 a quarter. Payback time, thanks to our stupidly high prices of electricity is going to be less than 3 years for me. $8000 system cost total including interest as it’s on the solar quotes finance partner’s green loan. The repayments are far less than the bills I was getting. Now my bills are close to zero (is summer though).

        • Des Scahill says

          You are dead right that ‘summer weather and reverse cycle air con is where solar cleans up big time’… I’ve got a Fronius 5.0.1A ( which ‘technically’ only has a maximum output of 4.5 kw) along with 6.44 kw of panels). We are having hot dry weather here in Brisbane at present, and my system produced 39.6 kwh today, and I was still able to export 27kwh despite running a large Mitsubishi inverter reverse cycle air con from 9:00 AM to 5:00 PM.

          All up, overall the system saved me outlays of $7.44 for the day. We set the air-con at 24 degrees. One thing that ‘helps’ is…. most of the heat comes into a house through the plasterboard ceilings, and the temperature in the roof space can reach 50+ degrees centigrade. If you can lower the temp in the roof space, then that lowers the temperature differential between the above ceiling and below ceiling spaces, which in turn lowers the speed of heat transfer through the ceiling. Which means – if you can lower the temp of the air in the roof space, your air-con will have less work to do.. An ‘el-cheapo’ way of lowering the temperature is to move the internal ceiling manhole access cover (which is often in the garage) aside, which then creates an airflow of cooler air into the ceiling space, which then displaces the hot air out through the various small gaps and vents in the roof. (every bit helps :-))

          Just checked out the electricity prices for Adelaide residents vs Brisbane. Your 40.4 cents per kwh is exactly 50% higher than Brisbane rates for the same plan. To me, its as if the ‘distributor’ has deliberately set out to destroy his own business by giving everyone a huge ‘perverse incentive’ to install solar as soon as they possibly can.

      • Greg,
        You’re quite right. Put it down to me having been on a gross meter not a smart meter until the last quarter (so self-consumption was not applicable) and to me being a senile old fool.
        So, four to five years, depending – as you say – on swings and roundabouts.
        I’ll think about it once I’ve had the roof replaced.

  8. you say I can add 1/3 extra to my existing system over the value of the inverter. It sounds great, so I would in effect generate more electricity than I am now.
    but my current system is nearly 7yrs old (well and truly paid for itself over 2yrs ago)

    can I add to a system this old, should I be concerned if what I have now doesnt meet current standards, thanks in advance. Ill contact the original installer and ask them too, I currently get in qld 56c feed in,44c standard and 12 from the retailer and my energy cost from my retailer is now lower for what I buy than I paid in 2009.
    cheers and love your blo

    • Ronald Brakels says

      I’m afraid that unless your inverter meets modern standards you won’t be permitted to increase your panel capacity. I should have mentioned that in the article and I have now updated it. So if your old inverter dies and you decide to replace it with one of the same capacity then you could increase your panel capacity up to 133.3333333333…%

  9. 10% self consumption. You should base it off 30-50% at least.

    10% is for people who think 30 degree indoor temperature is nice, don’t ever watch television, probably don’t own a computer, and use gas ovens exclusively. Oh and they have a lights off policy at 7pm…

    Such people who go and buy a 6.5kw system are just scabs and it’s unrealistic.

    • I would think 10% self consumption is easily done with a 6.5kW system. Solar or gas HWS helps.
      We 3 adults have a 2.6kWh system that exports 10.7kWh this time of year and we only take about 1.5kWh from the grid. Usage calculation is about 4kWh/day.
      We aren’t hermits. Westinghouse did a study showing the average comfortable temp (with moving air) to be 27C. We use the AC when needed to achieve that and use misters to improve the AC efficiency.
      The now small Samsung 42 inch TV is LED backlit and uses about 40Watts per hour in energy saving mode and the TV gets used the average 5 hours/day.
      Small form factor PC, 2 laptops and one tablet. They too get way too much use.
      Bottled gas cooktop, solar oven when the sun shines and a very inefficient glass benchtop turbo oven. Most lights are LEDs so no lights off policy required.
      If being frugal and happy to export clean energy to my neighbours makes me a scab, I’m comfortable with that. As I am with the substantial credits that keep hitting my bank account.

      0.15t est. emissions⊗
      Daily Average

      27 Aug 2017 – 24 Nov 2017
      90 days

      Daily Average

      Current Bill Period~
      25 Nov 2017 – 22 Feb 2018
      90 days

      • $-376.65!!

        What’s (watts? 🙂 ) the electrical term for “I’ve got wood”? Sparked? Amped maybe?

        My best is $-352.09.

        • Well, I do get excited at the prospect of my credits but not quite “wood” excited.

          If we keep up the average -$5.79 this quarter the next one should be around $530 (including pay on time discount, which always gives me a chuckle)

          If I get the energy to go up and clean my panels, maybe more.

          • Not a good idea to climb up on the roof. What I do is: if I can see that the panels are dust covered, (due say to lack of rain) I stay on the ground with a hose, and set the nozzle so it generates a spray that is more or less equivalent to a light to medium shower, and arc the waterflow it so it more or less falls vertically on the panels. Then aim the spray on the panels starting at the top portion and work systematically downward, letting the run-off flow into the roof guttering.

            Should only do this very early in morning so the panels are cool, and production output is nil or miniscule.

            You’ll get about 90% of the same output benefit I reckon, no risk, and no fiddling around with ladders etc etc.

            Basically what I’m doing is ’emulating’ a natural rainfall on the panels from a height well above them in order to rinse them off during long ‘no rain’ periods. Seems to work pretty well if the colour of the water going into the guttering is any indication.

            (maybe I’m just lazy)

          • Ronald Brakels says

            I approve of this approach to cleaning panels and mention it in this article:


          • Hi,

            (including pay on time discount, which always gives me a chuckle)

            Yes, me too.

            Not a good idea to climb up on the roof.

            Definitely not if it’s damp, but otherwise OK. Depends on the footwear: thongs are bad.

            I use a Vileda, it has an extension handle, with a swivelling fine pad head. I can work off a ladder (can be as dangerous as getting on the roof – ask Molly!). I only do it once a year, or if I can see a fair bit of bird shit.


        • Yes, I think I have cleaned them twice in 17 Years but only early morning and definitely not when raining. I’m pretty comfortable on the roof and use a window squeegee on a long aluminium pole.
          There is definitely a short term benefit.

          • Des Scahill says

            On my original 1.5 Kw system, I got a magnificent .25 Kw per day increase in the TOTAL daily production… (somewhere between 3 and 5%). So the ‘benefits’ from keeping your panels clean are there,but will vary depending on a host of factors in each case.

            Also – one can be ‘penny-wise and pound foolish’. I’ve got a colour-bond roof – unless one is very careful where one steps you can cause ‘small gaps’ in the weather seal at the lower end of a sheet (where it overlaps the sheet underneath it). Can seem an insignificant problem until you get 100 kph gale. That’s sufficient to reverse rain and water running down the roof, backwards up under the sheeting overlap and into the roof space. It then trickles along interior beams/trusses etc and can end up on your plaster ceiling some distance from where it entered, making it extremely hard to locate the source.

            Of course, you’ll never know for quite some time that’s happening if you have fibreglass batts – until the weight of a cubic meter or so of water (about 1000 kg ) causes some of the interior plaster room ceiling to collapse.

      • So you’re on a like 50 something cents feed in? Of course you’d be scabby or frugal with such a high feed in. Damn, I’d love $376 back every bill. I’d start feeling comfy with a piece of turd evap air con in 100% humidity too with feed in that high. I’d also start to believe that 27c is a nice cool temp to fall asleep at. Hell any temp would be nice.

        In all seriousness though, if you started getting 6-18c FIT and you had 6.6kw, you’d start eating some of that nice free power instead of letting the power company mark it up by over 100%.

        Hence my point that 10% self consumption is unrealistic for most people.

        • 60.3c kWh is a good incentive to use less. There are two main camps in the solar rooftop consumer world. Those of us who are environmentally driven and enjoy the financial benefits and those who install rooftop solar to save money.
          Being in the former category, we have also made gradual (affordable) “green” home improvements that enable us to use less power and still be comfortable.

          I think the average use in SA is down to 15kWh/day now and with LED lights becoming cheaper and other appliances TVs, fridges etc. becoming more efficient (as well as high energy prices) I expect that will drop. Some people will take a more hands on approach after installing PV with the aid of metering to reduce usage even further.

          I have relatives who take the approach of using more as they have ample self generation but once saving habits are ingrained they are hard to break.

          In 2028 (when the PFiT runs out) I will probably go off grid and be 100% self consumption.

          • Wow 60cents FIT is more than 3 times as good as my feed in of 18c. Feed in wise your 2.6 is acting like something over 8kw…

            I won’t lie, I did it mostly for the money savings as running ducted reverse cycle without solar seems a little crazy to me. The environment is a very nice bonus.

            Looking for battery options too in the future too. That would be more for environment and to be self sustainned… and because SA power are a joke.

    • Not sure what your reasoning is Angela ???

      There’s different ways of calculating ‘self-consumption’.

      In my case the numbers are:

      My total electricity consumption is : 13 Kwh per day.

      I ‘self-consume’ about 8 kwh, which is a portion of the total produced by my panels.

      So my ‘self-consumption can be also be expressed as 8/13 or 61.5%

      The other 5 Kwh is roughly my night-time consumption – which I still get billed for.

      Basing ‘self-consumption’ on the total output from a solar system makes meaningful comparisons difficult and can be quite misleading.

      Any solar production over and above the 8 kwh I self-consume is exported, at a rather measly FIT rate. Which btw helps keep prices down for ALL non-solar system owners. Or it would if the power distributors weren’t so involved in the retail price-setting process. And if successive governments hadn’t in the past also completely stuffed up their ‘renewable energy’ policies.

    • Ronald Brakels says

      People who are out of the house for most of the day and have a 6.5 kilowatt solar system are supplying a lot of clean green electricity to the grid that reduces fossil fuel generation and these days they don’t receive what I think is a fair price for it. So I’d like to thank everyone who generates more electricity using solar than they consume.

  10. I originally installed an older style 1.5 KW SMA Sunny Boy inverter, with sixteen 110 watt thin film hybrid Kaneka panels. The panels were installed all facing pretty much North ( 10 degree azimuth away from North toward the East), which used most of the available optimum north facing space on my gabled colour-bond roof.

    My basic choices for my new system were: relocate the existing panels to face westerly, and install sufficient new panels facing northerly to bring me up to the 5 KW limit.
    “scrap” the existing 1.5 Kw system and install 2 strings of new panels facing ‘north’ and ‘west’.

    The cost difference between the 2 alternatives was $450. Remounting the old panels ( ie. un-install then reinstall elsewhere on roof ) is a VERY costly and time consuming exercise from the installers point of view.

    From checking old power bills etc, I was able to calculate that not only had I recovered my original outlay for the 1.5 system, I’d also benefited from virtually zero electricity bills for nearly 7 years due to the high FIT. I’d clearly got my money’s worth out of the system.

    However, with the advent of higher tariffs, plus ‘standing charges’, I was now going backwards if I just kept the old system and did nothing.

    Now, its NOT a good idea to simply take the old panels to the tip – you might find yourself having to refund some of the STC credits you were given on the ‘old’ system. (which could set you back a heap of cash).

    So – retaining the ‘old’ panels is currently a must in QLD. The older style 1.5 SunnyBoy (with heaps of internal copper wiring) is not one I would on-sell to some-one else. There is an extremely remote possibility that the inverter might burst into flame ( only about 3 or 4 cases world-wide over more than a million installations). You maybe could be in heaps of trouble if the person you sell your second-hand inverter to doesn’t install it properly and THEIR house, holiday shack, or farm shed gets burned down. For the very few bucks I might get for it, its simply NOT worth it. Would I re-use it myself? Maybe. Would I sell it to some-one else? No.

    Back to the panels… the reality is that virtually no-one wants sixteen 110 watt panels. My installer didn’t want my old system, and left the inverter, panels and their associated mounting frames with me after installing my new system. The old panels each weigh 18.3 kilos, and the 16 panels take up 20+ square metres of roof space.

    The resale value of ‘old’ 1.5 systems is nothing to get excited about. The market resale price of panels varies from 35 to 50 dollars each, while the resale value of an entire system with inverter can be as low as $700. You’ll find a few systems for sale on GumTree.

    No idea yet what I’ll do with the ‘old’ panels – still mulling over a few ‘alternatives’.

  11. Hi,

    I installed a small system in 2011. Not cheap, even with rebate. A year later, I wanted to upgrade, but of course would have lost my PFiT, I thought: “stuff that!” Instead, I installed a separate 3kw system, with a solar controller, batteries & inverter (UPS), to run most of our house. I worked that it would pay for itself well before the PFiT ends, due to the extra we would export. Haven’t had a debit bill since, and have had > $2000 rebates.

    When PFit does end, the original system’s panels will be “tacked on” to the 2nd system via another solar controller. No way will give my electricity away, then pay to buy it back!

    Slightly off-topic, but I have noticed that we now qualify for a reduction in “Service to Property” charges, as the usage charges are lower than the StP charges. Good move, the less you use, then less you pay. An incentive to use less power (not that I needed one).


    • HI,

      Sorry, a correction, > $3000, though I suppose $3000 is > $2000. But for accuracy (pedanticness? ;p), I had to.


      • I’ve been contemplating the same set up but as our use is so low (4kWh/day) I’m having trouble justifying.
        Interesting about the StP charge reducing. I;m in SA and have never heard of it which is shame as it seems a fairer system than a standard daily charge.

        • Hi,

          I should have mentioned that we have concession cards (Health Care), but like you, I hadn’t heard of it. I checked or last “bill”, and it was on there too. Shows how well I study them. Really, I only look at the credit part. Took me a year to realise our “Winter Energy Concession for Gas” wasn’t being applied!

          I was wrong (AA) about how it works, it’s worked out that if the service charges are higher than usage, the StP is reduced so that it’s no greater than usage.

          IMHO, that should be the same for everybody!


  12. Hi,

    I have a question about this:

    Victoria: A minimum of 60 cents a kilowatt-hour with a retail feed-in tariff of at least 11.3 cents on top of this, making for a minimum feed-in tariff of 71.3 cents.

    How is it possible to get this? I’m with Origin, they give an extra 6 cents, and have done so so since inception AFAIK, but at least since 2011. They were the highest, and there are no fees for receiving a credit, unlike some at the time. There may have been one or two at 68/70 cents but with fees. Sorry, off the track a bit!



    • dRdoS7,

      See Ronald’s article above, under the heading “Existing High Feed-In Tariffs And Their End Dates”.

      The Victorian 60c Premium Feed-in Tariff is a legacy rate and was no longer available to new entrants after the end of 2011.

      So probably you are about six years too late. :>


      • Hi,

        I do have PFiT, until 2024, and I receive 66 cents, but don’t see how I can up it to 71.3.

        I’ve had a read in a few places, but none mention adding the new minimum of 11.3 to a 60 cent PFit.



  13. I have received a couple of notifications of copies of a post (apparently duplicated) be Des Scahill, from about 8 hours ago, that does not show above.


    In that post, is

    We set the air-con at 24 degrees. One thing that ‘helps’ is…. most of the heat comes into a house through the plasterboard ceilings, and the temperature in the roof space can reach 50+ degrees centigrade. If you can lower the temp in the roof space, then that lowers the temperature differential between the above ceiling and below ceiling spaces, which in turn lowers the speed of heat transfer through the ceiling. Which means – if you can lower the temp of the air in the roof space, your air-con will have less work to do.. An ‘el-cheapo’ way of lowering the temperature is to move the internal ceiling manhole access cover (which is often in the garage) aside, which then creates an airflow of cooler air into the ceiling space, which then displaces the hot air out through the various small gaps and vents in the roof. (every bit helps :-))

    One thing that is relatively cheap, and, effective, is (in addition to the fibreglass batts insulation in our roof) what I did to our roof, shortly after we moved into this house (that we bought, not rented), about 25 years ago.

    I bought a wind turbine (if that is the correct name for it – from memory, it is) roof air extraction vent thing, and, installed that just below a main ridge on about the middle of the roof area, and, eave vents around the eaves, about every 3m or so, so that air would be venting the roof space continually, to reduce moisture and heat accumulation in the roof space. It probably cost about a couple of hundred dollars, all up, and, because the roof is a tile roof, installing the whirlygig (that may be another name for it ) thing, was a DIY job, probably taking about an hour or so. We have sealed eaves all around the house, so, venting them, and, venting the roof space, is good for reducing the heat and moisture accumulation in the roof apace, and, I believe, reduced the potential heat radiation from the ceilings.

    It is a (I believe, relatively) simple way of increasing household energy efficiency, and, effective household maintenance.

    And, … I think it reduces the risk of critters coming into the house, via the manhole cover opening being left open as suggested by Des.

  14. Des Scahill says

    Thanks for your comments Brett. I’ve got a colour bond corrugated roof, and the insulation method used was to affix a foil material which has attached/glued to it a layer of thin insulatory material directly to the underside of the colour bond itself.

    As well, like a lot of houses built in QLD over the last 20 years or so, basically there are no eaves. Instead, window shades are used on outside windows, except for those windows which are already fully shaded by patio and verandah roofs.

    That doesn’t completely rule out whirlybirds though, as I can cut vents in some of the patio and verandah areas. However I looked at them as the first alternative, they don’t seem terribly effective

    For various reasons I don’t like fibreglass batts – even though they are a good insulating material.

    The only other alternative I’ve found (so far) is the ‘SolarWhiz’ – a solar powered fan system ( see ), but I’d probably need a couple of them.

    I’m still weighing that one up, ( after all, currently it costs me virtually nothing to run my air-conditioners) but it would reduce the load on them. So for the time-being… I simply removed the roof space access cover as an ‘interim solution’.

    Rather ironically, I’d probably find I wouldn’t need to use my air-conditioners much at all if I installed the solar whiz product

    One ‘Heath Robinson Contraption’ to the possible problem of vermin entering through my open roof access cover is to either drill small holes into the existing cover, or maybe build a new ‘cover’ that uses steel mesh fly screen mounted on fly screen security material.

  15. David Arthur says

    Ronald, what happens to the graphs if you standardise the self consumption of the original 1.5kW system vs the proposed 6.5kW system? On the 1.5kW system at 33% it is using 0.5kW daily whereas the 6.5kW system is using 30% more (ie 0.65kW). The same 30% inequity occurs on the second part of the graph.

    Am I right in thinking that the majority of people wont timeshift power too much and hence the ‘actual’ daily consumption needs to be matched. In this case the 1.5kW system needs to have the self consumption figures modified to make the actual consumption the same kW usage. This will reduce their value and make changeover more competitive.

  16. Andrew Hunter says

    I pulled out my old 1.5kw and installed new 5 kw system – I work from home and use around 60% of what we generate . So I now have the old system sitting in my shed and my shed has a large flat roof. Can I install the old system on the shed just to run my off-peak hot water

    • Ronald Brakels says

      If you want to make an off-grid solar system to power your hot water system then old inverter won’t be suitable for that use. If you want to use it on-grid then I’m certain your old inverter won’t meet current standards and you won’t be allowed to connect it. You may be better off getting a hot water diverter which will send surplus solar power that would normally be exported to the grid for a feed-in tariff to your hot water system. Or it may be cost effective to leave your hot water system as it is and perhaps look for ways to improve energy efficiency.

      • I’m about to fit this and 1kWp to my solar hws. Only one element so fingers crossed it covers our needs in Winter.
        It would be ideal for a storage tank with two elements but I’m not sure how popular they are in Oz.

        • David Arthur says

          Rod, not sure on the device you link.

          An alternative that MAY work – investigate a DC element for the hotwater – I am not sure if you require a controller between the panels and element.

          Given that the smallest AC element I am aware of is 1.8kW, Ron is correct that your old inverter cannot power the hotwater.

          The problem you could run into on the standalone system (either method) is you have no ability to introduce grid power. My hotwater timer can be overridden by pressing a button giving it grid power if required. A twin element (with top element connected to grid) may provide this ability to add grid as a backup.

          • According to the blurb it is just the panels and MPPT/booster. Yes, unfortunately only one element on my tank (3kw) and I understand it is either the PV booster or grid back up but not both.
            My 3 flat panel solar HWS does a great job 9 Months of the year and I’m 90% hopeful this solution will add enough heat to the tank to get us through a couple of consecutive mid winter, overcast days.
            This is a fairly inexpensive experiment if it fails miserably.

  17. James Dodds says

    I have a 1.6 KW system that I have had for 10 years. The original inverter failed after a few years (a Sharp JH-1600E) and was replaced under warranty with an identical unit. It has failed again with d-21 code which I am sure was the result of a close lightning strike but it is out of warranty (> 5 years old). I go my energy provider (Origin) to quote for a replacement and they recommended a 1.5 KW Goodwe 1500-XS with a quote of $2,236 which includes labour, new earth cable ($440) 1 Rooftop DC w/cover and rail $250 4x Conduit run $162 and 7 X Earthing correction $315. Does this sound excessive. I note that the inverters are $530 -590 online. I am on the 49 c feed in tariff in QLD. Have no further north roof but do have some west facing roof.
    Any advice?

  18. Thanks for all the helpful articles. Just a note about current situation in Queensland. Above you mention: “In Queensland, while the inverter size can’t be increased, it is possible to increase the panel capacity up to a maximum of one-third more than the inverter capacity, but only if your inverter meets modern standards.” So far when I have spoken to installers, they say I can only have panels up to same as inverter, not 133%. Doing some googling it seems like the rules changed from 15 Feb 2018, and oversizing was no longer allowed. So when you article was written your statement was probably correct, but no longer so.

    • Finn Peacock says

      I think you are talking about the specific situation where you are on the old Premium Feed-In Tariff (44c). That has specific rules for upgrading to which you must adhere – to keep the 44c until 2028.

      90%+ of QLD solar owners on a regular Feed In tariff can oversize their solar-only system by 133% compared to inverter AC capacity.

Speak Your Mind

Please keep the SolarQuotes blog constructive and useful with these 5 rules:

1. Real names are preferred - you should be happy to put your name to your comments.
2. Put down your weapons.
3. Assume positive intention.
4. If you are in the solar industry - try to get to the truth, not the sale.
5. Please stay on topic.

Please solve: 27 + 7 

Get the latest solar, battery and EV charger news straight to your inbox every Tuesday