A 6.6 kW system is the most common size on Australian roofs, so it is the best test of the deeming schedule. The figures below use the formula 6.6 kW x zone rating x deeming years, rounded down.
STCs by zone and year
| Install year | Years | Zone 1 | Zone 2 | Zone 3 | Zone 4 |
|---|---|---|---|---|---|
| 2026 | 5 | 53 | 50 | 45 | 39 |
| 2027 | 4 | 42 | 40 | 36 | 31 |
| 2028 | 3 | 32 | 30 | 27 | 23 |
| 2029 | 2 | 21 | 20 | 18 | 15 |
| 2030 | 1 | 10 | 10 | 9 | 7 |
Zone 3 covers Sydney, Brisbane, Perth, Adelaide, Canberra, the Gold Coast, Newcastle, Wollongong, Cairns and Townsville. Zone 4 is Melbourne, Geelong, Hobart and Launceston. Darwin is zone 2 and Alice Springs zone 1. Check your own postcode in the STC calculator.
What it is worth
Using a price of $38 to $40 an STC, which is roughly where spot has been at the time of writing, a zone 3 system’s discount is:
- 2026: about $1,710 to $1,800
- 2027: about $1,370 to $1,440
- 2028: about $1,030 to $1,080
- 2029: about $685 to $720
- 2030: about $340 to $360
These are illustrative: the price is not fixed, and the figure a customer sees on a quote is the installer’s own number. The count of STCs is set by rules; the dollars are not.
Who gets the money
The household normally assigns the STCs to the installer and receives the value as a discount on the quote. See do installers keep the STC discount for how to read that line, and how STCs are paid for the trail after installation.
What this means for you
If you are a homeowner weighing up when to install, the fall from 2026 to 2027 is about $350 to $360 on this system at today’s prices. That is a real number but not the only one: panel prices, tariffs and your usage matter as well. See should you install solar now or wait. Installers can quote off the calculator and sell certificates at the published rate on pricing.
For deeming mechanics read the deeming period page; start trading if you install.