The standard Australian rooftop system has been creeping upward for a decade. What was 5kW became 6.6kW, then 10kW, and 13kW is now a routine quote rather than an unusual one.
That shift is driven less by falling panel prices and more by what households now plug in. An electric vehicle, a heat pump hot water system, induction cooking and reverse-cycle heating can double a home’s annual electricity use, and a system sized for a gas-connected house from several years ago will not cover it.
The question is whether 13kW is the right answer for your roof or simply the biggest number on the quote. Here is the full picture: cost, realistic output, space requirements, and the specific household profiles where this size genuinely earns its place.
What a 13kW system actually consists of
A 13kW system refers to the combined DC capacity of the panels, not the inverter rating. With panels in the 440W to 480W range now standard, you are looking at roughly 27 to 30 panels. Older or lower-wattage panels push that closer to 33.
Allowing around 1.95 to 2.2 square metres per modern panel, expect to need in the region of 60 to 70 square metres of usable roof after setbacks, obstructions and access clearances are deducted. That is a meaningful footprint, and on a complex roof with several small faces, it often means splitting the array across multiple orientations. Our guide to solar panel size, dimensions and weight gives the measurements to work against.
Inverter sizing follows separately. Australian rules allow the array to exceed the inverter rating by up to a third, so a 13kW array commonly runs on a 10kW inverter. This oversizing is deliberate and beneficial: it keeps the inverter working closer to its efficient range for more of the day and lifts morning and afternoon output, at the cost of trimming a small amount of peak production on the clearest days.
What it costs installed
For a quality 13kW system with reputable panels, a well-regarded string inverter and professional installation, expect roughly $11,000 to $16,000 installed after the federal STC discount has been applied, including GST.
That is a wide band, and the spread is real rather than a hedge. The variables that move it:
- Panel and inverter tier. Premium panels and a premium inverter can add several thousand dollars over mid-tier equipment.
- Roof type and access. Tile is more labour-intensive than Colorbond. Two-storey, steep pitch or restricted access adds cost, sometimes including scaffolding.
- Split arrays. Panels across three or four roof faces require more rail, more cabling and often optimisers or an additional MPPT.
- Switchboard work. Older boards frequently need upgrading before a system this size is connected.
- Microinverters or optimisers. Worth it on shaded or multi-orientation roofs, and they add to the price.
Quotes well below this range usually reflect something removed rather than efficiency, which we cover in our article on the cost of solar panels in Australia.
On the rebate itself, the STC discount is already deducted from the quoted price in almost every case. The number of certificates reduces each January as the scheme winds down toward its end date, which means the same system costs slightly more each year. Our STC rebate scheme guide explains the calculation.
Realistic output for NSW and QLD
Daily generation averaged across the year, for a well-oriented 13kW system:
| Location | Average daily output | Approximate annual output |
| Sydney | 48 to 52 kWh | 17,500 to 19,000 kWh |
| Newcastle and Central Coast | 48 to 52 kWh | 17,500 to 19,000 kWh |
| Regional NSW inland | 50 to 55 kWh | 18,000 to 20,000 kWh |
| Brisbane | 52 to 56 kWh | 19,000 to 20,500 kWh |
| Gold Coast and Sunshine Coast | 52 to 56 kWh | 19,000 to 20,500 kWh |
Treat these as planning figures rather than promises. Summer days on a clear north-facing roof can exceed 70kWh. Overcast winter days can fall below 20kWh. The annual average is what matters for a payback calculation, and it is what a credible quote should be built on.
Three things move your actual result more than anything else: orientation, shading and panel direction split. North maximises total annual output, while west-facing panels produce later into the afternoon, which matters more now that the evening peak is where the money sits. Our guide on which direction solar panels should face covers the trade-off, and how much electricity one solar panel produces explains the per-panel maths.
The export limit problem nobody mentions upfront
This is the single most important consideration with a system this size, and it is routinely skipped at quote stage.
Your network caps how much power you can push back to the grid, and that cap is set per phase. On a single phase connection with a 5kW limit, a 13kW system producing 50kWh a day will be throttled whenever household consumption is low and generation is high. On a spring weekday with the house empty, a substantial share of that generation is simply never produced.
Three phase connections multiply the allowance, which is why 13kW systems sit far more comfortably on three phase properties. Some networks, including Ausgrid, permit more per phase than others, and flexible export arrangements can lift the cap further where the local grid has capacity.
None of this means a 13kW system on single phase is a bad idea. It means the value has to come from self-consumption rather than export, which changes the design brief entirely. Have your installer confirm your specific export limit in writing before you commit to this size.
Who a 13kW system genuinely suits
Work from your bills, not from ambition. Look at twelve months of consumption in kilowatt-hours.
Below about 6,000 kWh a year: 13kW is oversized. A 6.6kW or 10kW system will serve you better and the surplus capital is better spent on storage.
Around 8,000 to 10,000 kWh a year: borderline. An 8kW or 10kW system is often the sharper buy unless you have a specific reason to go larger.
Above roughly 10,000 to 12,000 kWh a year, or over 30 kWh a day: 13kW starts to make clear sense.
The profiles where it consistently stacks up:
- EV households. A car covering 15,000km a year needs roughly 2,500 to 3,000 kWh of charging. Charging during daylight from your own roof is the single best use of a large array, as covered in our guide to solar and EV charging.
- All-electric homes. No gas connection means hot water, cooking, heating and cooling all draw electricity. Consumption of 35 to 50 kWh a day is normal.
- Pool owners. A pump running six to eight hours daily is a substantial, and conveniently daytime, load.
- Home businesses and daytime occupancy. Daytime load is the best possible match for solar, since it is consumed directly rather than exported at a few cents.
- Large families with ducted air conditioning. Summer and winter peaks both land hard.
- Planned electrification. Installing capacity now for an EV or heat pump arriving within a couple of years is reasonable, provided the timeline is real.
- Large unused roof area. If north and west faces are sitting empty, filling them costs comparatively little per additional kilowatt since labour and compliance costs are already committed.
For properties operating as premises rather than homes, commercial solar brings tax treatment and larger system economics into play.
Should you pair it with a battery?
With feed-in tariffs now sitting at a few cents per kilowatt-hour, exported surplus is worth little. A 13kW system produces considerable surplus. The logic follows.
For a household at this consumption level, 13kWh to 20kWh of usable storage is the usual landing zone, with the federal battery discount taking a meaningful share off the installed cost. Our guides on sizing a battery and the federal solar battery rebate cover the specifics, and our comparison of feed-in tariffs versus storage sets out why the economics have shifted.
If your budget forces a choice, a 10kW system plus a battery usually beats a 13kW system with no battery, because stored energy displaces grid power at full retail rate while exported energy does not.
Payback
Most 13kW installations in NSW and QLD land in a four to seven year payback window, assuming a reasonable proportion of generation is self-consumed. The variable that moves it most is not system size or price, it is the self-consumption rate.
A household consuming 60% of its generation directly will pay the system off years ahead of one exporting most of it. That is why the household profile matters more than the headline kilowatts.
The short version
13kW is the right size for high-consumption, electrified households with the roof to support it, ideally on three phase or paired with storage. It is the wrong size for an average household choosing it because bigger sounds better.
Pull your last twelve months of consumption, check your export limit, then size to the answer.
Greenlight Solar designs systems against actual consumption data and confirmed network conditions across NSW and QLD. Compare components in our guide to the best solar panels in Australia, or request a quote for your roof.
FAQ:
How much roof space does a 13kW system need?
Roughly 60 to 70 square metres of usable area once setbacks, vents, skylights and access clearances are excluded. Complex roofs often need the array split across multiple faces.
How much power does a 13kW solar system produce per day?
Around 48 to 52 kWh daily on average in Sydney and 52 to 56 kWh in Brisbane, with clear summer days running considerably higher and overcast winter days considerably lower.
What size inverter do I need for 13kW of panels?
A 10kW inverter is the common pairing. Australian rules permit the array to exceed inverter capacity by up to one third, and this oversizing improves output across the shoulders of the day.
Can I install a 13kW system on single phase power?
Usually yes, subject to network approval, but export will be limited to your per-phase cap. The design should then prioritise self-consumption and storage rather than export, and your installer should confirm the applicable limit before you sign.
Is a 13kW system too big for an average home?
For a household using under about 6,000 kWh a year, yes. It suits homes above roughly 10,000 to 12,000 kWh annually, which generally means an EV, a pool, full electrification or significant daytime load.
What is the payback period on a 13kW solar system?
Commonly four to seven years in NSW and QLD. The decisive factor is the share of generation consumed on site rather than exported, since self-consumed energy is worth several times the feed-in rate.
Does a 13kW system need three phase power?
Not technically, but three phase substantially increases the export allowance and makes the size more comfortable. Upgrading purely to raise an export cap is rarely worthwhile, since the same money generally delivers more as storage.
