How the federal discount works
When an accredited installer fits an eligible battery, they create STCs for it and usually take their value off your price upfront. Your STC count is:
usable kWh × STC factor, with the factor applied in full up to 14 kWh, at 60% from 14 to 28 kWh, and at 15% from 28 to 50 kWh. Capacity over 50 kWh earns nothing. The result is rounded down.
Worked example · from the government’s explanatory statement
25 kWh, May 2026: (14 × 6.8) + (11 × 6.8 × 0.6) = 140.08 → 140 STCs A 25 kWh battery certified in May 2026 gets 140.08, rounded down to 140 STCs. Enter 25 kWh above and you'll get the same count.
The discount falls every six months
| Installed | STC factor per kWh |
|---|---|
| Jan – Apr 2026 | 8.4 |
| May – Dec 2026Now | 6.8 |
| Jan – Jun 2027 | 5.7 |
| Jul – Dec 2027 | 5.2 |
| Jan – Jun 2028 | 4.6 |
| Jul – Dec 2028 | 4.1 |
| 2029 | 3.6, then 3.1 |
| 2030 | 2.6, then 2.1 |
The factor that applies is the one on your installation date. A battery installed in December 2026 gets 6.8 per kWh, but one installed in January 2027 gets 5.7, about 16% fewer STCs. If you've already decided to buy, book the install before the next drop.
What to check before you sign
- Usable vs nominal capacity. STCs are based on usable capacity, which is often less than the headline figure.
- The STC line on the quote. Multiply the STC count by the price per STC and check it matches.
- Approved products and installers. The battery must be on the Clean Energy Council's approved list, installed by an accredited installer.
- Bigger isn't always better value. Above 14 kWh, each extra kWh gets 60% of the discount, and above 28 kWh only 15%. See what size you need.