The factor is the number of STCs per kWh of usable capacity before the tier weighting is applied. It is set by schedule and it falls over time, which is why the date of installation matters as much as the size of the battery.
The schedule
| Install window | Factor |
|---|---|
| Jul to Dec 2025 | 9.3 |
| Jan to Apr 2026 | 8.4 |
| May to Dec 2026 | 6.8 |
| Jan to Jun 2027 | 5.7 |
| Jul to Dec 2027 | 5.2 |
It continues stepping down towards 2030. At the time of writing, 6.8 is current, 5.7 applies from 1 January 2027 and 5.2 from 1 July 2027.
How much will the battery rebate be in 2027
The kWh-weighted sums below use the tiers (first 14 kWh at 100%, 14 to 28 at 60%, 28 to 50 at 15%) and round down.
| Battery | 6.8 (now) | 5.7 (Jan 2027) | 5.2 (Jul 2027) |
|---|---|---|---|
| 10 kWh | 68 | 57 | 52 |
| 13.5 kWh | 91 | 76 | 70 |
| 20 kWh | 119 | 100 | 91 |
| 28 kWh | 152 | 127 | 116 |
| 50 kWh | 174 | 146 | 133 |
On a 13.5 kWh battery, the move to 5.7 removes 15 STCs, or about $570 to $600 at a spot of $38 to $40. The move to 5.2 on 1 July 2027 takes away another 6.
January 2027 at 5.7
The January step is the one most people have heard about. It is a cut of about 16% to the factor, so every battery size loses roughly 16% of its certificates. The January 2027 cut explainer covers the planning side.
July 2027 at 5.2
The July step is smaller, about 9% on top of January. It is easy to miss because it falls mid-year, which makes it a quieter deadline for installers who are used to thinking in calendar years.
Pulling the date forward
Because the install date sets the factor, a delay at any stage can cost certificates: stock, switchboard work, grid approvals or a booked electrician slipping into January. Installers should build buffer into jobs targeting the last weeks of December and June.
Why the schedule falls
The factor is designed to keep the discount at roughly the same share of the battery price as hardware costs fall. If battery prices keep dropping, the smaller factor can still deliver a similar percentage discount, which is why a lower STC count does not always mean a higher out-of-pocket cost.
What this means for you
Homeowners deciding whether to wait should compare a lower discount against battery price movements and any retailer or VPP offers, not the STC count alone. Use the battery STC calculator to test dates. Installers can read the battery STC overview and the installer guide, and see published settlement rates on the pricing page.