Until this year, a solar system above 100 kW created no STCs and had to register as a power station and earn LGCs year by year. From 1 October 2026 that changes for systems above 100 kW and up to 1 MW: they create STCs at install with a fixed five-year deeming period. The Renewable Energy (Electricity) Regulations were amended in 2026 and the Clean Energy Regulator (CER) has said applications open in mid to late November 2026.
The numbers
The calculation is the same as for small systems: kW x zone rating x 5, rounded down. Zone 3 is 1.382 and zone 4 is 1.185.
| System size | Zone 3 | Zone 4 | Zone 3 value at $38 to $40 |
|---|---|---|---|
| 200 kW | 1,382 STCs | 1,185 STCs | $52,516 to $55,280 |
| 250 kW | 1,727 STCs | 1,481 STCs | $65,626 to $69,080 |
| 500 kW | 3,455 STCs | 2,962 STCs | $131,290 to $138,200 |
| 1 MW | 6,910 STCs | 5,925 STCs | $262,580 to $276,400 |
The dollar column uses roughly $38 to $40, the range the STC market has traded in at the time of writing, with a clearing house ceiling of $40. A 500 kW zone 3 system is therefore worth in the order of $131,000 to $138,000 upfront. Treat these as planning figures: confirm the zone rating and any size-specific rules with the CER before you quote.
Zones and the five-year rule
Unlike the small-system deeming period, which counts down to 1 year in 2030, the mid-scale band is reported as a fixed five years. That makes forward planning easier but means the zone, not the date, is the main variable. Zone 3 includes Sydney, Brisbane, Perth, Adelaide, Canberra, Newcastle and Wollongong. Zone 4 includes Melbourne, Geelong and Hobart. Darwin is zone 2 and Alice Springs zone 1.
STCs versus LGCs at this size
An LGC is created per MWh generated after the system is accredited, so the income arrives over years and depends on the LGC spot price, which has been oversupplied and cheap in 2026. The verified spot was roughly $6 to $9 in September 2026 after a low near $4 in February. STCs front-load the value at install. For comparing the two, see mid-scale solar STCs and STC vs LGC.
What this means for installers
For a commercial job the certificate value is a material part of the customer’s payback, so the count belongs in the proposal. Three practical points:
- Systems installed before 1 October 2026 stay under the old rules. Check the date that counts for your job.
- Photos, serials and approved panels still apply. Larger jobs get more scrutiny, not less.
- Cash flow is the big change. A single job can create thousands of certificates, so check how a buyer settles before you commit. See the commercial cash flow answer.
To estimate smaller systems use the table in STCs by system size or the STC calculator. For the settlement side see STC trading and pricing.