Straight answers, 2026
What size solar system do I need?
The short answer
Divide your daily power use by the peak sun hours where you live, then add about 25 percent. In South East Queensland and northern NSW, a home using 15 to 35 kWh a day needs about 6.6 kW to 10 kW.
Sizing method as used by Ray, our solar advisor. Prices as at 21 August 2026. By Verified Solar. Last updated .
Start with your daily usage
Your electricity bill shows your average daily usage in kWh. That number, not the size of your house or how many people live there, is what decides the system.
If you already have solar, the bill only shows what you took from the grid, which is far less than you actually use. Add what your panels produce, or the new system will come out much too small.
Divide by your peak sun hours
Peak sun hours are the equivalent number of full-strength sun hours your roof gets on an average day. South East Queensland and New South Wales both average about 4.2.
Your daily usage divided by 4.2 gives the smallest system that would cover it on an average day. Ray then adds about 25 percent on top.
Worked examples
For a home in South East Queensland or northern NSW, solar only, no battery:
| Daily usage on your bill | Recommended system and price |
|---|---|
| 15 kWh a day | 6.6 kW, about $5,280 to $7,260 |
| 25 kWh a day | about 7.4 kW, about $5,920 to $8,140 |
| 35 kWh a day | about 10.4 kW, about $8,320 to $11,440 |
Why 6.6 kW is the floor
Ray never recommends less than 6.6 kW for a new system, even for a low-usage home. That is the smallest size worth installing, so a 15 kWh a day home and a 20 kWh a day home get the same answer.
What the roof decides
The calculation gives the size your usage needs. Whether it fits depends on the roof: the space, which way it faces, and shading. An installer confirms that on site, and on a small or shaded roof higher efficiency panels can fit more output into the same space.
Common questions
Is 6.6 kW enough for a family home?
It covers about 22 kWh a day in South East Queensland and northern NSW. If your bill shows more than that, a larger system will usually suit you better.
Should I size my solar bigger if I am getting a battery?
Often, yes. The panels need to run the home during the day and charge the battery as well. Ray works out both together from your bill.
Does a bigger system always save more?
Not always. A system much larger than your usage mostly sends power back to the grid rather than running your home. That is why the size starts from your bill.
Get the answer for your home
Tell Ray your bill and what you are after. He sizes the system and explains the rebates before anyone quotes you. Free, and no details needed to start.