6.6kW Solar Systems: Costs, Output, and Returns

House roofs with solar panels installed in suburban area of South Australia

6kW solar systems or now more commonly seen as 6.6kW solar systems are becoming increasingly popular amongst Australian homes thanks to a number of factors, including their affordability, ample size & ease of approval when it comes to connecting to the grid. This article provides an overview of (almost) everything you need to know if you’re considering a 6kW solar system for your household, including pricing, energy yields and their attractiveness as an investment.

How many panels are in a 6.6kW solar system? How much area required?

A modern-day 6.6kW solar system using 330-watt (W) to 400W modules will consist of about 17-20 solar panels. This number has reduced a lot over the last decade.

Each panel generally measures out to 1.7m2, so the roof area required for a 6.6kW system will be about 34-38m2 – or possibly more depending on how your roof is laid out and whether you require tilt frames (which need to be spaced out more than panels mounted flush on the roof).

An important note about inverters for 6kW/6.6kW solar systems

Are 6.6kW systems the new 5kW system?

Although your system may have 6.6kW worth of solar panels, don’t be surprised if the proposed inverter for your system is only 5kW. 5kW solar systems are also incredibly popular in Australia for a number of reasons (including the fact that that size is pre-approved for grid connection on basically every network in the country), which means that 5kW inverters are much more common to come across than 6kW ones. Many of the 6.6kW solar systems on the market are therefore ‘overclocked‘ systems with a 5kW inverter.

A 5kW inverter can be overclocked by a maximum of 33% under the Clean Energy Council guidelines to 6.6kW but can’t quite get to 7kW which would require a larger inverter. This offers benefits such as greater solar energy yields in the early morning and late afternoon – even if ‘peak’ production is clipped back to 5kW during the middle of the day.

How much does a 6.6kW solar system cost?

Solar Choice has been keeping track of residential solar system prices since August 2012 with our monthly Solar PV Price Index. Based on this data we can advise that the average 6.6kW solar system will cost around $0.98 per watt or $6,460 after the federal STC rebate has been deducted as of July 2023.

See the full breakdown by Australian city in our table below which we update each month:

6kW solar system costs by Australian state capital

Adelaide, SA$5,580
Brisbane, QLD$5,150
Canberra, ACT$5,730
Darwin, NT$9,320
Hobart, TAS$6,430
Melbourne, VIC$5,380
Sydney, NSW$4,990
Perth, WA$5,420

The price of solar systems do, however, vary widely in the market. A more cost-competitive 6.6kW solar PV systems consisting of cheaper, low-end products will cost less, while premium offerings will generally be pricier.

History of 6kW solar system prices in Australia

The below graph shows the price history of the last couple of years. You can see the pricing has remained relatively flat however there are some differences depending on your location in Australia.


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How much energy will a 6.6kW solar system produce?

Depending on a number of factors, the actual power output of a 6kW solar power system will vary. These variables include:

  • Location and local climate
  • Orientation and tilt angle of the solar panel array
  • Whether there is any shade cast on the panels
  • The performance of the individual components (primarily the panels and inverter)

Location is one of the main determinants of solar system energy yields, as the amount of sunshine falling on a solar system’s solar panels directly affects the system’s output. The table below provides rough approximations for how much energy a 6kW solar system will produce, based on Bureau of Meteorology and PVWatts data.

Please note that these figures are indicative only and that we have endeavoured to be conservative in our estimates, using a system efficiency rate of 75%. Also, note that these figures are annual averages – in reality, energy yields will be higher in the summer and lower in the winter.

Energy output from a 6.6kW solar system

Capital CityApprox Solar Energy Production* (per day)
Adelaide24-26 kWh
Brisbane25-27 kWh
Canberra24-27 kWh
Darwin28-30 kWh
Hobart19-22 kWh
Melbourne21-24 kWh
Perth26-28 kWh
Sydney22-25 kWh

* Estimates generated using Burea of Meteorology historical weather data and PVsyst software

Batteries with a 6.6kW solar system?

More and more households have battery storage in mind when they purchase a solar system. The smallest size we generally recommend you install if you’re considering batteries either now or in the future is 5kW; a system of this size will generally provide plenty of surplus energy for storing. At slightly larger than 5kW, 6kW systems would also be a good size for batteries.

Further reading:

Is solar battery storage worth it?

How long is the payback period on a 6.6kW solar system?

The benchmark by which most solar shoppers measure their panel’s performance is the payback period – the number of years that the system will take to ‘pay for itself in energy bill savings & feed-in tariff credits.

The table below shows indicative payback periods, ‘internal rate of return’ (IRR) and annual savings in the first year for 6.6kW solar systems in a handful of Australian capital cities based on average prices as of July 2023. (Note that these are outputs from our Solar System Payback & ROI Estimator tool – which we encourage you to explore with your own numbers.)

Keep in mind that returns may be better for systems whose price points are lower, or if you achieve a higher level of solar self-consumption. But also be mindful that you’ll want to be selective about the products and companies that you consider – some deals are too good to be true.

Indicative payback periods for 6.6kW solar systems 

 6.6kW System CostElectricity PriceFeed in RateSelf Consumption RateIRRAnnual SavingsPayback Period (Years)


  • Average daily energy use = 25 kWh
  • 6.6kW System cost is the average price from Solar Choice’s price index for a fully installed turnkey system
  • Excludes state-based solar grants/rebates (e.g. Solar Victoria rebate)
  • Pricing comes from Solar Choice’s Price Index for July 2023

Calculate your own solar payback period using Solar Choice’s free payback calculator.

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Since 2008 our knowledge and sophisticated software has allowed over 300,000 Australian households and businesses to make a well-informed choice on their solar & battery installer.
Jeff Sykes


  1. Hi Solar Choice,
    Looking at getting solar and the more I do the more confusing it seems to be, no two quotes alike.

    One I am favouring are quoting a 6.8Kw Canadian 340w 144 cell x 22 panels with Fronius 6kw phase inverter and Fronius Smart metre for full monitoring purposes Solar PV for $8800.00

    Everyone else has quoted using a 5 kw inverter and I am advised while a bit more expensive it will in the long run give me more of a return on a cheaper electricity bill.

    My quarterly bills are currently averaging out at $670.00

    If you are able to offer any advise I would indeed be grateful.

    Thank you Simon

    1. Hi Simon,

      Solar panel arrays are allowed to be oversized relative to the inverter capacity – so a 5kW inverter with 6kW worth of panels is relatively common these days. When you take this approach, your solar system will produce a bit more energy in the mornings and afternoon, but will flatline in the middle of the day, when the sun is at its brightest. The overall effect is that you get more energy out of a 6kW solar panel / 5kW inverter system than you would out of a 5kW panel / 5kW inverter system – especially during the times that you’re likely to use it (morning & arvo).

      This approach is particularly attractive for two reasons: 1) Some electricity networks only allow up to 5kW of inverter capacity to be connected without extra red tape, and 2) 5kW inverters are very common and therefore often less expensive than other ‘niche’ sizes because of the amount of competition in this size range. So you might find a a good deal in a system that oversizes the panel array.

      It sounds like the 6.8kW Canadian / 6kW Fronius inverter setup that you’re currently leaning towards is a decent quality system – on the ‘premium’ end of things. According to our pricing figures, a ‘premium’ 7kW solar system retails for about $1.20 per watt – or about $8,400 on average nationally (we don’t have specific pricing for 6kW systems, so I encourage you to check out the table and look for your nearest capital city). I also note that this price doesn’t include extras like monitoring, so that could explain the higher price you’re looking at (and also: some places have higher overall prices – especially VIC and TAS).

      I hope this helps!

  2. What is the rebate rate of the solar power installed 2 years ago?
    It was 68 cents but we got a letter from the service prowider ( AGL ) it is 60 cents now. We changed from Origine because it paid only 66 cents…
    Is there a better deal with any of other company?
    Do you have a list I can select from?

    Thanks a lot

    1. Hi Attila,

      I think you’re referring to feed-in tariffs as opposed to a rebates. Regardless the options available to you will depend on what state you live in. Unfortunately, we don’t have a comprehensive list of what’s on offer from energy providers as we help people get the best solar PV installation deal for them. I’d recommend you have a look at a comparison site for energy company’s.

      As a rough guide, the base level in NSW two years ago was 60¢ per KWh, although energy retailers did offer various options to encourage people (like yourself) to switch. There is currently no mandatory feed-in tariff in NSW so switching to another energy provider may result in you loosing the 60¢ rate, the best on offer in NSW is now 8¢ per KWh! If you speak to AGL they may be able to tell you why the rate was dropped and their competitors may by able to advise as to whether you will still be eligible for the earlier Premium tariff.

      Sorry we can’t be of more help, good luck!

  3. Thank you for your independent assistance as there is so much information that I obviously don’t understand.
    As I have had “my fingers burnt” with Chinese manufactured goods (they seem to provide cheap & only lasting 1/4 or 1/3 of previous products & so I don’t buy to throw out as I don’t like our disposable age !! Graeme

    1. Graeme,

      Thanks for the comment. Both premium and bottom-shelf solar products come out of China, as well as a number of mid-range ones. The old motto goes ‘you get what you pay for’. We’ve had many a customer who has gone ahead with systems that use Chinese components and been happy with them. There may be more of a guarantee of quality from European brands, but with a bit of discrimination it is also quite possible to find quality components with a ‘Made in China’ label.

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