If you are asking “how many solar panels do I need”, the honest answer is that it depends on how much electricity you use, how much roof space you have and where in Australia you live. The good news is that you can get a solid estimate in a few minutes using nothing more than a recent power bill. This Australian sizing guide walks through the simple maths so you can work out the right solar system size before you talk to any installer.
We will start with your daily usage, move through worked examples by household size, then cover panel wattage, roof space and when it pays to size up for a battery or EV.
Start with your daily usage
The single most useful number for sizing a system is your average daily electricity consumption, measured in kilowatt hours (kWh) per day. You can find this on your electricity bill, usually shown as a daily average or as a total for the billing period that you divide by the number of days.
As a rough national picture, Australian homes use somewhere between 10 and 25 kWh per day, depending on household size, climate and appliances. Once you know your figure, you can size a system to cover a healthy share of that usage during daylight hours.
A handy rule of thumb is that each 1 kW of solar produces roughly 4 kWh per day on average across Australia, though this varies with location and season. So a 6.6 kW system generates around 26 kWh on a good day, which is why it remains the most popular reference point for Australian homes.
Worked examples by household size
The table below gives indicative sizing for typical households. Treat these as starting points, since two homes of the same size can use very different amounts of power.
| Household | Typical daily usage | Suggested system size | Approximate panel count (440W) |
|---|---|---|---|
| Small (1-2 people, unit or small home) | ~8-12 kWh | 5-6.6 kW | 12-15 panels |
| Medium (3-4 people, 3 bedroom house) | ~14-20 kWh | 6.6-8 kW | 15-18 panels |
| Large (5+ people, big home) | ~22-30 kWh | 10-13 kW | 23-30 panels |
| Large + battery or EV | 30 kWh+ | 13 kW+ | 30+ panels |
For a common question, solar panels for a 3 bedroom house typically land in the 6.6 kW to 8 kW range, which suits a family using the dishwasher, washing machine and air conditioning across the week.
The panel wattage maths
Working out the number of solar panels is straightforward once you have a target system size. Modern residential panels are commonly around 440 watts each in 2026, though they range from roughly 400W to 500W.
To find the panel count, divide your system size in watts by the panel wattage:
- 6.6 kW system = 6,600W divided by 440W = 15 panels
- 10 kW system = 10,000W divided by 440W = around 23 panels
- 13 kW system = 13,000W divided by 440W = around 30 panels
Higher wattage panels mean fewer panels for the same system size, which helps when roof space is limited. Lower wattage panels are sometimes cheaper but take up more room.
Quick formula to remember
Number of panels = (system size in kW x 1000) divided by panel wattage. Keep your panel wattage handy from your quote and you can sanity check any installer’s proposal in seconds.
How much roof space do you need
Each modern panel is roughly 1.8 metres by 1.1 metres, so about 2 square metres including mounting gaps. As a rough guide:
- 6.6 kW (15 panels): around 30 square metres of roof
- 10 kW (23 panels): around 45 square metres
- 13 kW (30 panels): around 60 square metres
North-facing roof sections are ideal in Australia because they capture the most sun across the day. East and west faces still work well and can actually suit households that use most of their power in the morning and evening. Shading from trees, chimneys or neighbouring buildings reduces output, so usable space matters more than total roof area.
Peak sun hours by city
The same system produces more in sunnier regions. Peak sun hours describe the daily average of full-strength sunlight a location receives. The table below shows indicative annual averages.
| City | Approximate daily peak sun hours |
|---|---|
| Brisbane | ~5.0 |
| Perth | ~5.0 |
| Adelaide | ~4.5 |
| Sydney | ~4.0 |
| Melbourne | ~3.6 |
| Hobart | ~3.3 |
A home in Brisbane will generate noticeably more from a 6.6 kW system than the same system in Hobart, so a southern household may choose to size up slightly to reach the same annual output.
When to size up for a battery or EV
If you are planning to add a battery or buy an electric vehicle, it usually makes sense to install more panels now rather than later. A battery needs surplus daytime generation to charge, and an EV can add several kWh of demand each day depending on how far you drive.
Oversizing your array means you produce enough to power the home, charge the battery and top up the car, all while still exporting some excess for a feed-in credit. Since the cost per panel falls as the system grows, going from 6.6 kW to 10 kW is often a small step up in price for a meaningful jump in output. With the federal battery rebate now available, more households are sizing their solar with storage in mind from day one.
When you are ready to get accurate numbers for your roof, it helps to compare solar companies and request tailored quotes. You can also browse residential solar installers or filter solar companies by state, since sizing advice and pricing differ across regions like South Australia.
Frequently Asked Questions
How many solar panels do I need for a 3 bedroom house?
A typical 3 bedroom house in Australia suits a 6.6 kW to 8 kW system, which is around 15 to 18 panels at 440W each. Your actual number depends on your daily usage and how much power you use during the day.
What size solar system do I need?
Work out your average daily usage in kWh from your bill, then aim for a system that comfortably covers your daytime consumption. Most Australian homes land between 6.6 kW and 10 kW. Larger households or those adding a battery or EV often go higher.
How many kWh does one solar panel produce per day?
A single 440W panel produces roughly 1.5 to 2 kWh per day on average, depending on your location, roof orientation and the season. Sunnier regions and north-facing roofs sit at the higher end.
Should I oversize my solar system?
Often yes. Because the cost per panel drops as the system grows, adding extra capacity is usually inexpensive and gives you headroom to charge a future battery or EV and export surplus power for a feed-in credit.
Why is 6.6 kW such a common size?
A 6.6 kW system suits the typical Australian home, fits most roofs, qualifies well for the STC rebate and pairs neatly with common 5 kW inverters. It is a sensible default, but bigger households should still check their own usage.
Get a sizing quote for your roof
The best way to confirm how many solar panels you need is to have an accredited installer assess your roof, orientation and usage. Compare your options and request quotes from CEC-accredited installers by browsing the directory to compare solar companies today.