The zone decides how many certificates each kW of solar earns. It comes from the postcode where the system is installed, using the Clean Energy Regulator’s (CER) postcode table, and it reflects how much sunshine that part of the country gets.
Zones by city
| Zone | Rating | Typical locations |
|---|---|---|
| 1 | 1.622 | Alice Springs |
| 2 | 1.536 | Darwin |
| 3 | 1.382 | Sydney, Brisbane, Perth, Adelaide, Canberra, Gold Coast, Newcastle, Wollongong, Cairns, Townsville |
| 4 | 1.185 | Melbourne, Geelong, Hobart, Launceston |
Most of the population is in zone 3, which is why it is the one quoted in most examples. Melbourne and Hobart sit in zone 4, so identical systems earn about 14 per cent fewer STCs there (1.185 against 1.382).
Why a postcode and not a city
The CER table works at postcode level, and some regional postcodes sit in a different zone from the nearest capital. A property on the edge of a zone can differ from the rest of its suburb. Always look up the exact installation postcode instead of guessing by city, and use the postcode of the site, not the owner’s mailing address.
How to check your zone
- Take the postcode of the installation address.
- Look it up in the CER’s postcode zone table, or enter it into the STC calculator, which applies the zone for you.
- Confirm the zone rating and the deeming period for the install year.
For battery STCs the zone does not apply, because batteries are calculated by usable kWh and a factor; use the battery STC calculator.
What the zone means in certificates
For a 2026 install, with a five-year deeming period:
- Zone 3: 6.91 STCs per kW. A 6.6 kW system gives 45.
- Zone 4: 5.925 per kW. A 6.6 kW system gives 39.
- Zone 2: 7.68 per kW. A 6.6 kW system gives 50.
- Zone 1: 8.11 per kW. A 6.6 kW system gives 53.
See the full set of sizes in STCs by system size, and the ratings across years in zone ratings by year.
What this means for installers
The zone is on the STC claim, and a wrong postcode means the wrong certificate count. A common mistake is using the customer’s billing postcode or a nearby suburb. Check the install address against the registry entry, and keep the evidence in the job file. See how STC audits work.
For the broader context see deeming period and zone ratings and the STC trading pillar.