The battery STC factor converts a battery size into a certificate count. Take the usable capacity in kWh, multiply by the factor, and you have the number of STCs, subject to tiering for larger batteries.
The numbers
| Install date | Factor |
|---|---|
| 1 May to 31 December 2026 | 6.8 |
| From 1 January 2027 | 5.7 |
The factor then falls again in later years towards the end of the program in 2030. Because it changes with the date, always check the Clean Energy Regulator before quoting past a changeover.
How the tiers interact with the factor
Since 1 May 2026 the factor applies in full to the first 14 kWh of usable capacity. Capacity from 14 to 28 kWh earns 60 per cent of the factor, and 28 to 50 kWh earns 15 per cent. Nothing above 50 kWh earns certificates. For a 20 kWh battery in 2026 the maths is 14 x 6.8, plus 6 x 6.8 x 0.6, which is about 95 plus 24 STCs, around 120 in total.
Certificates are issued as whole numbers, so expect rounding down at the end. Rely on the Clean Energy Regulator’s calculator or the portal output for the final count, not a spreadsheet.
Why the factor matters to your quote
A one-point change in the factor does not sound large, but across a 14 kWh battery it is 14 certificates, or around $550 at the current market. The cut from 6.8 to 5.7 is therefore about $600 on a single 14 kWh job at current prices. Our pillar page on battery STCs tracks the current position.
Where to check the current factor
The factor is published by the Clean Energy Regulator and set in regulations, so it is the one number you should never take from a brochure or a colleague. Check it on the regulator’s battery pages when you quote, and again before lodging a claim near a changeover date. If your quoting software hard-codes a factor, it needs a date-driven lookup.
What this means for installers
Build the factor into quoting software as a date-driven lookup rather than a hard-coded number. Add the tiers, rounding and the 50 kWh cap. For the broader process see how to claim battery STCs and the battery submission guide.