Start with your bill, not your house
Pull out a recent electricity bill and find your average daily usage in kilowatt-hours (kWh). That single number is the best starting point for sizing — far better than bedrooms or floor area.
Then ask how much of that usage happens in daylight. A retired couple home all day and a family who leave at 7am have very different ideal systems even with identical bills.
Roof space and orientation set the ceiling
- North-facing gives the best total output across the day.
- East and west split output towards morning and afternoon, which often matches household usage better than a pure north array.
- South-facing panels still produce in Queensland, just less — worth using when it's the only space left.
- Shading from trees, chimneys, aerials and neighbouring buildings matters more than most people expect; a small shadow at the wrong time can cut a whole string.
- Your roof's usable area is the hard limit. On a tight roof, higher-output panels buy you more kW in the same footprint.
Export limits and inverter sizing
Your network sets rules on how much you can install and export, and those limits differ between single-phase and three-phase properties. Systems above certain thresholds may need extra approval or export limiting.
Inverters are commonly slightly undersized relative to the panel array — that's deliberate, and it improves output across morning and afternoon rather than losing yield. What matters is that the ratio stays inside the manufacturer's and the CEC's rules.
We check your supply type and network limits before quoting so the design you're sold is the design that gets approved.
Should you oversize?
Panels are the cheapest part of a solar system, and the labour, scaffolding and paperwork are largely fixed. Going a step bigger while the installer is already on your roof is almost always cheaper than adding panels later.
Oversizing makes the most sense if you're planning an EV, a pool, ducted air-conditioning, a battery, or a home extension. It makes least sense if your roof is heavily shaded or your network caps exports tightly.
Common questions
Is 6.6kW still enough?
For a low-usage household, yes. But with EVs, air-conditioning and batteries becoming normal, most families we quote now end up larger than that if the roof allows it.
Will a bigger system void anything with my network?
No, but larger systems can need additional approval or export limiting. We handle that application as part of the job.
Can I add panels later?
Sometimes, depending on inverter capacity and the age of the existing system. It's almost always cheaper to size it right the first time.
Want this checked against your own bill?
We'll give you a system size, price and payback estimate for your actual roof and usage.