A solar battery rebate calculator only needs three inputs: the usable capacity of the battery, the factor for the year it will be installed, and the price of a certificate. You can do the sum in a minute.
Step 1: find the usable kWh
Use the usable capacity from the datasheet or the Clean Energy Council product listing, not the number in the product name. Cap it at 50 kWh, because nothing above that earns certificates.
Step 2: apply the tiers and factor
For 2026 installs the factor is 6.8. Count the first 14 kWh at 100 per cent, the next 14 kWh at 60 per cent, and the next 22 kWh at 15 per cent. From 1 January 2027 the factor is 5.7, and from 1 July 2027 it is 5.2.
Worked example for a 14 kWh battery installed in 2026: 14 x 6.8 = 95.2, which rounds down to 95 STCs.
Worked example for 20 kWh: 14 x 6.8 = 95.2, plus 6 x 0.6 x 6.8 = 24.5, a total of about 119 STCs.
Step 3: multiply by the STC price
At the time of writing the market has been roughly $38 to $40 per STC. For 95 STCs that is about $3,600 to $3,800. For 119 STCs it is about $4,500 to $4,800.
Why the answer is an estimate
The installer’s discount depends on the rate their trader pays. That rate sits a little below spot and is published by each trader; ours is on the pricing page. The certificate price also moves, and the battery factor changes every 1 January and 1 July.
What this means for you
Use the calculation to compare quotes. Two installers quoting the same battery should show a similar STC count, and any difference in the discount should reflect only the certificate rate they use. Ask each to show both. Our battery STC pillar covers the program, and how the battery rebate is calculated explains the rules behind each step.