Is rooftop solar worth it in Australia? Payback explained

Rooftop solar is one of the few big-ticket energy upgrades that genuinely pays back fast in Australia. But the numbers depend a lot on system size — and the feed-in tariff matters far less than most people think.

The short answer

For most homes, a 6.6kW system is the sweet spot, paying back in about 5 years. A 3kW or 10kW system takes closer to 6 years. In sunny cities like Brisbane and Sydney, paybacks can be as quick as 3–4 years.

System size	Typical saving/yr	Rough payback
3 kW	~$730	~6 years
6.6 kW	~$1,340	~5 years
10 kW	~$1,630	~6 years

Why self-consumption beats the feed-in tariff

This is the bit the sales pitch usually skips. The value of solar comes overwhelmingly from the power you use yourself, not the power you export.

• Every kWh you use from your own panels avoids buying it from the grid at ~36c/kWh.
• Every kWh you export earns a feed-in tariff of only ~4c/kWh (and falling).

That’s a 9-to-1 difference. So the goal isn’t a giant system — it’s a system sized to what your home actually uses during the day. A typical home self-consumes about 35% of a 6.6kW system’s output; bigger systems self-consume a smaller share, which is why 10kW doesn’t pay back any faster than 6.6kW.

What your roof does to the numbers

The paybacks above assume a reasonably solar-friendly roof. Most roofs are — but a few site factors move the numbers, and it’s better to know them before the quotes arrive than after the install. None of these usually kill the case; they change what system you should buy and what a fair quote looks like.

• Orientation. North-facing is the ideal in Australia. East or west still works — you give up some total output, but generation shifts to morning or late afternoon, which can actually suit your usage (and self-consumption) better than a midday peak you’re not home for. A steep, purely south-facing roof is the one genuinely weak case.
• Shading. The factor that punishes hardest. Panels are usually wired in strings, so a shaded corner can drag down more than its own share — and the tree that’s fine today keeps growing. A good installer models shading rather than hand-waving it; microinverters or optimisers can rescue a partly shaded roof, at an extra cost that belongs in your payback maths.
• Roof space. A 6.6kW system is around 15 panels — a big, mostly unshaded roof face. If your usable roof is smaller or broken up by vents, skylights and valleys, you may be choosing between a smaller system and higher-wattage (pricier) panels. A smaller system on a good roof beats a big system squeezed onto a bad one.
• Roof age. Panels stay up for 25+ years. If the roof under them will need replacing in five, do the roof first — removing and reinstalling a system is an expensive way to learn this one.
• The real-world haircut. Averaged across installed systems, actual output typically runs 10–20% below the ideal calculator number once orientation, shading, dust and age are counted. If a sales projection assumes perfection, ask what your roof’s number is — a good installer can show you.

What about a battery?

A battery is a different decision, and we’ll be straight about it: at today’s prices, a home battery is generally about backup and self-supply — not necessarily a money-maker.

The arbitrage spread (buying at 36c, “saving” the 4c you’d have exported) is about 32c/kWh, which on energy alone doesn’t cover the cost of most batteries within their warranty — even after the federal Cheaper Home Batteries discount. For most households, the honest case is blackout protection and using more of your own solar.

The exception worth knowing about: a small number of retailers now offer wholesale-price plans where a battery buys power when it’s cheap and sells into price spikes, which can meaningfully improve the earnings. But it’s a hands-on strategy, the returns ride on volatile spike prices, and it deserves its own article. If you’re not planning to actively manage it, judge the battery on backup and self-supply.

The verdict

Solar: worth it for most homes, and 6.6kW is the size to beat — just get the shading and orientation looked at properly before you sign. Battery: for most people, buy it for backup and self-supply, and go in with eyes open on the payback.

Figures use the sourced assumptions from the Decode Energy Home Energy Saving Guide (AU 2026 edition). Capital costs are shown after the federal STC discount. Your numbers will vary with your roof, usage and tariff.