How the calculation works
Each kWh your battery supplies in the evening is a kWh you don't buy at your peak rate. That kWh was charged from solar you would otherwise have exported, so you also give up the feed-in credit. Yearly savings ≈ daily kWh used × 365 × (peak rate − feed-in tariff), plus any VPP payments. Payback = your cost after discounts ÷ yearly savings.
This is a simple estimate. It ignores battery degradation, round-trip losses, tariff changes and days your solar can't fill the battery (winter in the south). Treat a result close to the warranty length as marginal.
What makes a battery worth it
- A big gap between your import rate and your feed-in tariff. This is the single biggest driver, so read both off your bill.
- Using lots of power in the evening. Cooking, heating or cooling, and EV charging after sunset all count. If you're home in the day and already use your solar, a battery has less to do.
- Enough solar to fill it. Without solar, a battery can still charge on cheap off-peak or "free hours" plans, but the savings depend entirely on that plan's rates.
- Sizing. A battery bigger than your evening use sits partly empty. The Smart Energy Council found 6–7 kWh would cover evening peak use for over 90% of households (reported by ABC News). See our sizing tool.
- Timing. The federal discount drops every six months (next drop: 1 January 2027). Use our rebate calculator.
State-by-state extras
| State | On top of the federal discount (as of 24 Oct 2026) |
|---|---|
| NSW | VPP connection incentive (PDRS); the amount varies by provider |
| WA | Up to $1,300 (Synergy) or $3,800 (Horizon Power), and you must join a VPP |
| ACT | Sustainable Household Scheme loans |
| VIC, QLD | No state battery rebate open |
| SA, TAS, NT | Not yet verified by us, so check your state government site |