Where the previous page runs the sum on one battery, this page is about planning the whole budget so that nothing surprises you after the rebate has been taken off.
The budget in four lines
- Battery and inverter. Installed price for the usable kWh you need.
- Site extras. Switchboard work, cabling, conduit, backup circuit, meter changes and any approval costs.
- Minus the STC discount. Usable kWh, tiers and the factor for your install year, times the certificate value.
- Minus or plus anything else. State incentives, VPP sign-up credits, interest-free loans, or a trader margin that reduces what the installer can pass on.
Where the rebate is strongest
The first 14 kWh earn the full factor. The next 14 earn 60 per cent and the next 22 earn 15 per cent. A household that sizes a battery to sit at or just under 14 kWh usually gets the most rebate per dollar of hardware. A larger battery can still make sense, but the rebate will cover a smaller share of the extra cost.
Timing and the factor
The 2026 factor is 6.8, stepping down to 5.7 on 1 January 2027 and 5.2 on 1 July 2027 (the factor now steps every six months to 2030). For a 14 kWh battery that is about $600 of discount lost at current prices. If hardware prices drop during 2027 that may offset it, but nobody can promise it. Make decisions on a quote you hold, not a forecast.
An example of a site extra
Suppose the battery quote is clean but the site visit finds that the switchboard needs upgrading before the battery can be installed. That cost is outside the STC discount, and it can be significant. It is better to learn it from a site inspection than from a phone call on installation day.
What this means for you
A realistic budget uses the final installed price after a site assessment, the discount at the certificate value shown on the quote, and any state or VPP extras that you have confirmed. See how much a battery costs after the rebate for a worked example and the VPP incentive stack for the extras. The battery STC pillar covers the program, and the installer guide shows what your installer needs to do.