Worked example · Australia
What does a bigger home battery add? A city-by-city comparison
For a typical evening-heavy home adding 6.6 kW of solar, the first 10 kWh of battery does almost all the work. In every capital-city region we modelled, going from 10 to 20 kWh adds less than $90 a year.
Reviewed 18 October 2026 · Illustrative, not advice for your homeExtra yearly saving from each 5 kWh of battery
The same household in each capital, on that state’s typical electricity and feed-in rates.
Swipe across the table to compare every battery size.
| Region | Solar alone saves | 0→5 kWh | 5→10 kWh | 10→15 kWh | 15→20 kWh | 10 kWh worth up to* | 10→20 kWh worth up to* |
|---|---|---|---|---|---|---|---|
| Sydney | $1,060/yr | $460 | $360 | $50 | $10 | $7,600 | $500 |
| Melbourne | $620/yr | $450 | $270 | $40 | $10 | $6,600 | $400 |
| Brisbane | $1,080/yr | $370 | $320 | $20 | $0 | $6,300 | $200 |
| Adelaide | $1,280/yr | $620 | $480 | $70 | $10 | $10,100 | $700 |
| Perth | $960/yr | $540 | $410 | $60 | $10 | $8,700 | $600 |
| Hobart | $1,100/yr | $240 | $140 | $10 | $0 | $3,500 | $200 |
| Canberra | $1,080/yr | $460 | $320 | $80 | $20 | $7,200 | $900 |
| Darwin | $1,540/yr | $370 | $320 | $30 | $0 | $6,300 | $200 |
*Total extra saving over 10 years, the most that step is worth paying for on a 10-year payback target, net of any discount. The household uses 5,500 kWh a year, mostly mornings and evenings, on each state’s typical rates (sources on each state page). Batteries charge only from spare solar. Calculated by Solvetted’s engine (version 0.1.0-preview) with Australian Government average solar output for each capital.
Perth in detail
The same pattern, drawn for the Perth example: each step up in capacity adds much less than the one before. Perth’s low daytime feed-in (2c) is why its first 10 kWh is worth more than in many cities.
Show as a table
| Battery size | Yearly saving from battery | Extra from last 5 kWh |
|---|---|---|
| 0 kWh | $0 | N/A |
| 5 kWh | $536 | $536 |
| 10 kWh | $947 | $410 |
| 15 kWh | $1,005 | $59 |
| 20 kWh | $1,013 | $7 |
Why the extra capacity adds so little
A battery only saves money on the energy it actually shifts: spare solar stored in the day and used in the evening instead of buying from the grid. This household uses about 10–11 kWh between 4pm and 7am the next morning. Once the battery can cover that, extra capacity mostly sits unused, except on the few days with a lot of spare solar and a lot of evening use.
The answer changes when your home uses more power at night, runs an electric vehicle or heat pump in the evening, or is on a time-of-use plan with an expensive peak. Backup needs can also justify a larger battery even when the savings don’t.
What this means before you get quotes
- Ask for quotes on two sizes and compare the extra price with the extra yearly saving.
- Federal battery support tapers above 14 kWh of usable capacity from 1 May 2026, so the discount on extra capacity is smaller too. See our battery discount guide.
- Results for your own home depend on your usage, plan and roof. Run the calculator with your bill.
Your home, your numbers
See what each battery size adds for you.
Enter one bill. No sign-up, and nothing is stored.