Payback is the net cost of the battery divided by the yearly benefit. The net cost is after the STC discount. The benefit is what the battery saves or earns each year. Published estimates for rebated batteries commonly sit around 6 to 10 years, but the range is wide because the benefit depends entirely on your tariff and usage.
Where the benefit comes from
Self-consumption. Solar exported at a low feed-in rate is stored and used in the evening instead of buying from the grid at the retail rate. The bigger the gap between the two, the better.
Time-of-use arbitrage. On a time-of-use tariff the battery can charge off-peak or from solar, then supply the peak window. A steep peak rate lifts the savings; a flat tariff leaves little to arbitrage.
VPP income. The Cheaper Home Batteries Program requires a VPP-capable battery, though you do not have to join a VPP. Joining can add bill credits or payments for letting the provider dispatch your battery in peak events. Terms vary and change, so treat any advertised figure as an offer, not a promise. Some states add their own VPP incentives; see battery rebate VPP incentive stack.
A way to run your own sums
- Take the installed price and subtract the STC discount, using the battery STC calculator.
- Estimate evening energy you would shift in a year, bounded by the usable kWh and your daily use.
- Multiply by the difference between your peak rate and your feed-in rate.
- Add any VPP credit you have in writing.
- Divide net cost by the yearly benefit.
| Scenario | Likely direction |
|---|---|
| Large evening use, steep peak rate, VPP credit | Faster payback |
| Low use, flat tariff, small solar | Slower |
| Battery oversized for usage | Slower, extra capacity sits idle |
Oversizing matters more because the discount tapers above 14 kWh, so extra capacity brings less rebate and may bring no extra saving. See which battery size gets the biggest rebate.
Worked illustration
Take a 10 kWh battery with a net cost of about $8,000 after the discount, as a round figure for illustration. If it shifts 8 kWh a day of solar into the evening and the gap between your peak rate and your feed-in rate is 25 cents per kWh, the saving is about $2 a day, or roughly $730 a year. That gives a payback near 11 years before any VPP income. Add $300 a year of VPP credit and it falls to about 8 years. Change the gap to 35 cents and it improves again. The point is not the answer but how sensitive it is to the rate gap.
From the desk: a retailer’s payback calculator is a sales tool. Ask for the assumptions: which tariff, what usage, what feed-in rate, and whether VPP income is included.
Also remember the rebate steps down: 6.8 at the time of writing, 5.7 from 1 January 2027 and 5.2 from 1 July 2027, which lengthens payback for later buyers. For the scheme basics, read battery STCs.