There is no flat rebate. The value comes from a calculation, and the answer depends on three things: the size of your system, where you live and the year you install.
The calculation
Certificates = system kW x zone rating x deeming years, rounded down. The zone ratings are 1.622, 1.536, 1.382 and 1.185. The deeming period is 5 years for 2026 installs and 4 for 2027. Multiply by the market price per certificate, roughly $38 to $40 at the time of writing, and you have the value.
| System | Zone 3, 2026 | Approx. value at $38 | Zone 3, 2027 |
|---|---|---|---|
| 6.6 kW | 45 certificates | about $1,710 | 36 certificates |
| 10 kW | 69 certificates | about $2,620 | 55 certificates |
Why quotes vary
Installers apply a price per certificate that reflects what they are paid. Some assume a conservative number, some a higher one. The discount on your invoice is the certificate count times that price. Ask to see both, so that you can compare the gap between two quotes properly.
Add-ons that may apply
If you are in Victoria and meet the household income cap of $150,000, a separate state rebate may apply. If you add a battery, a different federal formula applies, 6.8 certificates per usable kWh at the time of writing, 5.7 from 1 January 2027 and 5.2 from 1 July 2027, giving a large extra discount. See the battery calculator guide.
The timing effect
Because the deeming period steps down on 1 January, a system installed in December earns a fifth more certificates than the same system installed in January. If your install date is close to the changeover, ask the installer what they are assuming and who bears the difference if it slips.
What this means for you
Use the table above as a rough guide, then ask your installer for the exact figures. For an explainer on what certificates are, see the STC trading overview, the glossary and our article on what an STC is worth in 2026.