Start with how much power you use
| City | 2 people | 4 people | Solar to match 4 people |
|---|---|---|---|
| Sydney | 14.3 kWh/day | 20.0 kWh/day | 5.3 kW |
| Melbourne | 13.3 kWh/day | 15.9 kWh/day | 4.9 kW |
| Brisbane | 14.0 kWh/day | 21.0 kWh/day | 5.6 kW |
| Adelaide | 13.8 kWh/day | 19.3 kWh/day | 5.1 kW |
Matching your yearly use does not mean your bill disappears. Most solar is made in the middle of the day and most power is used in the morning and evening, so you will still buy power at night and export at midday. That is why many homes go a little bigger than their usage, or add a battery.
What limits the size you can install
- Roof space. A 440 W panel takes about 2 square metres. A 6.6 kW system needs around 30 square metres of usable roof.
- Roof direction. North is best. East and west work well; south faces lose a lot. See orientation and shading.
- Network rules. Single-phase homes often face inverter and export limits. See export limits.
- Inverter ratio. Clean Energy Council guidelines allow panels up to 133% of inverter capacity.
Common sizes and who they suit
| Size | Deemed output a day | Suits | Average price |
|---|---|---|---|
| 3 kW | 11.4 kWh | 1 to 2 people, small roofs | $4,130 |
| 5 kW | 18.9 kWh | 2 to 3 people | $5,550 |
| 6 to 6.6 kW | 25.0 kWh | 3 to 4 people, most family homes | $6,330 (6 kW) |
| 7 kW | 26.5 kWh | 4+ people, east and west roofs | $7,070 |
| 10 kW | 37.9 kWh | Large homes, EVs, batteries | $9,810 |
Plan for what is coming
An electric car or swapping gas appliances for electric ones can add a lot to your daily use. If either is likely in the next few years, it is usually cheaper to install the extra panels now. See charging an EV with solar.
Common questions
On AER benchmarks, a four person home uses roughly 16 to 30 kWh a day depending on the city, with Canberra and Hobart at the top. A 6.6 kW system is the usual choice, and bigger homes with pools, EVs or electric heating may suit 8 to 10 kW.
About 25.0 kWh a day averaged over a year in Sydney, Brisbane, Adelaide and Perth, and about 21.4 kWh in Melbourne and Hobart, on Clean Energy Regulator ratings.
It can be bigger than is worth paying for if most of the extra output is exported at a low feed-in tariff or cut off by an export limit. It makes sense if you will add a battery, an EV or electric appliances.
Sources
Rules and program details come from government sources. Prices are industry averages, named and dated where used. Last checked October 2026. Prices include GST unless we say otherwise.