BatteryWhat size home battery do I need in Australia? (2026 guide)
Updated 17 October 2026 · General information only, not personal financial or electrical advice.
Bigger isn't automatically better. Under the federal Cheaper Home Batteries rebate as it has worked since 1 May 2026, each kilowatt-hour above 14 kWh earns a smaller rebate, and every kWh above 28 kWh earns only 15% of the full rate (Clean Energy Regulator). The right size depends mostly on two numbers you can find yourself.
Number 1: how much power you use after the sun goes down
A battery earns its keep by covering the electricity you would otherwise buy from the grid in the evening and overnight.
- Download your smart-meter interval data from your retailer or distributor app.
- Add up the usage from roughly 5 pm to 7 am on typical days.
- If all you have is your bill, a common starting assumption is that 50–70% of household use happens outside solar hours (estimate; it varies a lot by household).
Number 2: how much spare solar you have to fill it
A battery can only store energy your panels don't already use during the day.
- In QLD, a 6.6 kW system produces roughly 25–30 kWh on an average day (estimate).
- Take away your daytime use. What's left is the most you could store.
- If that leftover is smaller than the battery, the battery won't fill most days, especially in winter.
A simple rule of thumb
- Lower end: the smaller of your evening use and your spare solar.
- Upper end: about 20% above your evening use, plus an allowance for efficiency losses (round-trip efficiency is roughly 90%, estimate).
- Go above that only for a clear reason: blackout backup, a planned EV or pool pump, or a virtual power plant (VPP) arrangement you understand.
How the rebate tiers change the maths
| Usable capacity | Share of STC factor (from 1 May 2026) |
|---|---|
| 0–14 kWh | 100% |
| 14–28 kWh | 60% |
| 28–50 kWh | 15% |
| Above 50 kWh | 0% |
Source: Clean Energy Regulator, DCCEEW.
Households have already responded. The average battery installed dropped from 36 kWh in April 2026 to 23 kWh in May and June (CER Quarterly Carbon Market Report, June quarter 2026).
Always compare usable kWh
Rebates are worked out on usable capacity, and that's also the figure that matters for your bill. Check that every quote you compare states usable kWh, not just the nominal figure.
Want to run your own numbers? The BatterySorted calculator (Excel or Google Sheets) takes your bill, solar size, state and quote, then gives you a suggested size range, a rebate estimate and seven quote red flags. See the tools →
General information only. This is not personal financial or electrical advice. Get a site assessment from a licensed, accredited installer.