Informational Guide · Australia · 2025
How Many Solar Panels Do I Need in Australia?
A plain-language guide to calculating your panel count — by household size, state, and electricity usage.
Quick answer
Most Australian homes need 13 to 20 solar panels (a 5–8 kW system). A family of four using around 20 kWh per day typically lands on a 6.6 kW system — about 16 x 415W panels. Smaller households may need as few as 8, while large homes with an EV or pool can need 25 or more. The right number depends on your electricity usage, your state’s sun hours, and how much of your bill you want to offset.
Why panel count alone is the wrong question
When most people ask “how many solar panels do I need?”, they’re really asking “how big a system do I need?” Panel count follows from that — it’s just your system size divided by the wattage of each panel.
A 400W panel and a 420W panel both take up roughly the same roof space, but the 420W panel means you need fewer of them for the same output. So before counting panels, you need to know your system size in kilowatts (kW). Everything else follows.
The three numbers that determine your system size: your daily electricity use (kWh), your location’s peak sun hours, and a correction factor for real-world losses (typically 0.8).
Step-by-step: calculate how many panels you need
Find your daily electricity use
Pull up your latest electricity bill. Most bills show quarterly usage in kWh — divide that number by 90 to get your daily average. If you have a pool pump or are planning to charge an EV, add 20–30% to that figure.
Find your state’s peak sun hours
Peak sun hours aren’t total daylight — they’re the hours when sunlight hits at least 1,000 watts per square metre. Outside those hours, panels still generate electricity, just at a lower rate. See the table below for Australian averages by state.
Run the formula
Divide daily usage by peak sun hours, then divide by 0.8 to account for efficiency losses from heat, inverter conversion, wiring, and shading.
Convert kW to panel count
Divide your required system size in watts by the watt rating of the panel you’re considering. Most residential panels in 2025 sit between 400W and 440W.
The core formula
System size (kW) = Daily usage (kWh) ÷ Peak sun hours ÷ 0.8
Then: Panel count = System kW × 1000 ÷ Panel wattage
Worked example: Sydney household, 20 kWh/day
Sydney averages roughly 4.8 peak sun hours per day across the year. A household using 20 kWh daily needs:
20 ÷ 4.8 ÷ 0.8 = 5.2 kW system
The next standard size up is 6.6 kW — always round up, not down, because you want headroom. With 415W panels: 6,600 ÷ 415 = 16 panels.
Peak sun hours by Australian state
Where you live changes your calculation. Darwin gets more sun than Melbourne, which means a Darwin home needs a smaller system than a Melbourne home using the same amount of electricity.
| State / Territory | Avg. Peak Sun Hours / Day | System needed for 20 kWh/day | Panels at 415W |
|---|---|---|---|
| Queensland (Brisbane) | 5.2 hrs | ~4.8 kW → 6.6 kW system | 16 panels |
| Western Australia (Perth) | 5.5 hrs | ~4.5 kW → 5 kW system | 14–16 panels |
| South Australia (Adelaide) | 5.0 hrs | ~5.0 kW → 6.6 kW system | 16 panels |
| NSW (Sydney) | 4.8 hrs | ~5.2 kW → 6.6 kW system | 16 panels |
| ACT (Canberra) | 4.6 hrs | ~5.4 kW → 6.6 kW system | 16–18 panels |
| Victoria (Melbourne) | 4.4 hrs | ~5.7 kW → 6.6–8 kW system | 16–20 panels |
| Tasmania (Hobart) | 3.8 hrs | ~6.6 kW → 6.6–8 kW system | 18–20 panels |
| NT (Darwin) | 6.0 hrs | ~4.2 kW → 5 kW system | 14 panels |
Panels by household size
If you don’t have a bill handy, typical Australian consumption figures by household size give a useful starting point.
| Household | Typical Daily Use | Recommended System | Approx. Panels (415W) |
|---|---|---|---|
| 1–2 people / small home | 10–15 kWh | 3–4 kW | 8–12 panels |
| 3–4 people / average home | 18–25 kWh | 6.6 kW | 14–18 panels |
| 5+ people / large home | 28–40 kWh | 10–13 kW | 24–32 panels |
| Home + EV charging | 35–55 kWh | 13–15 kW | 32–38 panels |
| Home + pool pump | 25–35 kWh | 8–10 kW | 20–26 panels |
These ranges assume an average location of around 4.8–5.0 peak sun hours. Households in Queensland or Western Australia can use the lower end of each range; those in Melbourne or Hobart should use the higher end.
What the most common system sizes actually cover
Australia’s solar market has settled around a few standard sizes. Here’s what each one is designed to do.
3 kW (8–10 panels)
Suited to a single person or couple using 10–15 kWh per day. Once the most common size installed, it’s now considered small. The main drawback: you won’t be generating much surplus to sell back to the grid or store in a battery.
6.6 kW (14–18 panels) — the most popular choice
This is Australia’s sweet spot in 2025. Most solar installers won’t go smaller. A 6.6 kW system generates around 24–28 kWh per day in average Australian conditions — enough for a family of three to five people. It pairs well with a home battery and qualifies for strong STC rebates.
8–10 kW (20–26 panels)
Growing in popularity, especially for households adding a home battery, an EV, or a pool. An 8 kW system suits families using 28–35 kWh daily. The jump in cost from 6.6 kW to 10 kW is real, but so is the payback when you’re displacing that much grid electricity.
13–15 kW (32–38 panels)
For large homes, small businesses, or homes with two EVs. Requires a larger roof and a three-phase inverter in some configurations. Not common yet, but increasingly viable as panel prices fall.
Five factors that change your panel count
Roof orientation
North-facing panels produce the most year-round output in Australia because the sun tracks across the northern sky. East or west-facing arrays produce roughly 15–20% less output but work well, especially across a split-pitch roof. South-facing panels are avoided unless there’s no other option — output drops significantly, particularly in winter.
Shading
A single shaded panel in a string inverter system can cut the output of every other panel in that string. If part of your roof is shaded by a tree, chimney, or neighbouring building for even a few hours each day, discuss microinverters or a DC optimiser setup with your installer. The panel count stays the same, but the system design changes.
Panel wattage
Standard residential panels in 2025 sit between 400W and 440W. A 440W panel produces 10% more than a 400W panel in the same roof space. If your roof area is limited, higher-wattage panels let you fit more generation into fewer square metres. Each panel needs roughly 1.7–2 m² of space.
Battery storage
Adding a battery changes the math slightly. Without storage, you export excess daytime generation at a low feed-in tariff (usually 4–8 cents per kWh for new systems). With a battery, you capture that surplus for evening use instead. Homes with a battery can often get away with a slightly smaller panel array because less generation is wasted. Homes without a battery may want to slightly oversize to run high-consumption appliances during the day.
Future energy needs
Planning to buy an EV in the next two years? Installing a heat pump hot water system? Getting a pool? Size now for what you’ll need then, not just what you use today. Inverter and roof space constraints make retrofitting extra panels later possible but more expensive.
How the federal rebate affects your decision
Australia’s Small-scale Renewable Energy Scheme (SRES) issues Small-scale Technology Certificates (STCs) when you install solar. Your installer typically subtracts the STC value from your invoice upfront — you never see a cheque, just a lower price.
The number of STCs your system earns depends on its size, your location zone, and the number of years left before the scheme ends in 2030. A 6.6 kW system in Sydney currently generates a rebate worth roughly $3,000–$4,500. Larger systems in sunnier states generate more STCs and therefore larger upfront discounts.
From 1 July 2025, the federal government’s Cheaper Home Batteries Program also provides around a 30% discount on eligible home batteries — separate to your panel STCs, but working alongside them to improve the overall economics of going solar with storage.
Will your roof fit the panels?
Each standard residential panel takes up roughly 1.7–2 m² of roof area. A 6.6 kW system with 16 x 415W panels needs around 28–32 m² of usable, unshaded roof space. A 10 kW system needs 40–50 m².
| System size | Approx. panels | Roof space needed |
|---|---|---|
| 3 kW | 8–10 | 14–20 m² |
| 5 kW | 12–14 | 22–28 m² |
| 6.6 kW | 14–18 | 28–36 m² |
| 8 kW | 18–22 | 36–44 m² |
| 10 kW | 22–26 | 44–52 m² |
If your available roof space limits you to fewer panels than your calculation suggests, two options open up: use higher-wattage panels to extract more generation per square metre, or accept a smaller system and supplement with time-of-use habits (running dishwasher and washing machine during peak solar hours).
What to do with this information
The calculation above gives you a working estimate before you speak to a single installer. Here’s how to use it:
Before calling anyone, pull three months of electricity bills and calculate your daily average. If your bills show a wide seasonal swing (common in Melbourne or Canberra where heating loads are high in winter), base your calculation on the higher figure — solar typically produces less in winter, so sizing for your peak consumption month gives you better year-round coverage.
When you get quotes, check that the installer explains how they sized the system, not just what they’re recommending. A quote that arrives without a discussion of your consumption data or roof is a flag worth noting.
Ask about east-west split arrays if your roof doesn’t have a clean north face. Splitting panels across east and west slopes produces more total energy across the day than a pure north array for households that use electricity in the morning and evening rather than midday.
Get at least three quotes. The Solar Accreditation Australia (SAA) accreditation is the baseline — installers must be SAA-accredited for your system to qualify for STCs.
Frequently asked questions
How many solar panels does an average Australian home need?
An average Australian home using around 20 kWh per day typically needs 13–17 solar panels rated at 400W or above, making up a 6.6 kW system. Smaller households using 15 kWh per day may need 8–12, while large homes or those with an EV may need 20–28.
What size solar system is most popular in Australia in 2025?
The 6.6 kW system is the most popular residential choice. It suits families of 3–5 people using 18–30 kWh per day and typically consists of 14–18 panels depending on panel wattage. Most installers won’t recommend going smaller than this for a new installation in 2025.
Which direction should solar panels face in Australia?
North-facing panels produce the most energy year-round because the sun tracks across Australia’s northern sky. East or west-facing panels produce roughly 15–20% less, but a split east-west array can be better for households that use power in the morning and evening rather than midday. South-facing panels are generally avoided.
Does the Australian government offer a solar rebate?
Yes. The federal Small-scale Renewable Energy Scheme (SRES) issues Small-scale Technology Certificates (STCs) when you install eligible solar panels. Most installers subtract this value from your invoice upfront, reducing the purchase price by roughly $2,000–$5,000 for a 6.6 kW system depending on your location. The scheme runs until 2030 and the rebate steps down each year.
How much roof space do I need for solar panels in Australia?
Each standard residential panel takes up roughly 1.7–2 m². A 6.6 kW system (16 panels) needs around 28–32 m² of usable, unshaded north-facing roof. A 10 kW system needs 40–50 m². Your installer will assess your specific roof as part of the quoting process.
Can I add more solar panels later if I start with a smaller system?
Yes, but expanding later costs more than sizing correctly upfront. Your original inverter may not support extra panels, meaning you’d need a second inverter or an upgrade. If you think your energy use will grow — especially if you’re planning an EV or a battery — it’s worth sizing larger from the start.