Mid-scale solar is the new band under the Small-scale Renewable Energy Scheme: systems above 100 kW and up to 1 MW, installed from 1 October 2026. The calculation is the familiar one with the deeming period fixed.
The formula
STCs = kW capacity x zone rating x 5 years, rounded down.
The zone ratings are 1.622 (zone 1), 1.536 (zone 2), 1.382 (zone 3) and 1.185 (zone 4). Sydney, Brisbane, Perth, Adelaide, Canberra, Gold Coast, Newcastle, Wollongong, Cairns and Townsville are zone 3, Melbourne, Geelong, Hobart and Launceston are zone 4, Darwin is zone 2 and Alice Springs zone 1.
Worked examples
| System | Zone | Working | STCs | At $38 to $40 |
|---|---|---|---|---|
| 150 kW | 3 | 150 x 1.382 x 5 | 1,036 | about $39,400 to $41,400 |
| 300 kW | 4 | 300 x 1.185 x 5 | 1,777 | about $67,500 to $71,100 |
| 500 kW | 3 | 500 x 1.382 x 5 | 3,455 | about $131,300 to $138,200 |
| 1 MW | 3 | 1,000 x 1.382 x 5 | 6,910 | about $262,600 to $276,400 |
Values use the STC spot of roughly $38 to $40 at the time of writing and are indicative. Settlement rates for Energy Merchants are on the pricing page.
Compared with a small-scale system
Small-scale systems in 2026 also get five years, but the deeming period then drops to four for 2027 and one by 2030. Mid-scale systems have a fixed five, so the difference grows over time.
How to handle a 100 kW to 1 MW job as an installer
- Confirm the install date is on or after 1 October 2026 and that the system’s total onsite capacity falls in the band.
- Check the products are on the CEC approved lists and designed to the usual standards.
- Take the same on-site evidence you would for small-scale work: dated, geotagged photos at set-up, mid-installation and commissioning, with serial numbers.
- Collect the signed assignment of rights and the customer’s ABN and GST details, since commercial customers will want an invoice that shows the STC discount correctly. See RCTI, GST and ABN for STC payments.
- Decide the certificate pathway with the customer before lodgement. CER warns that choosing STCs prevents REGO certificates being created during the deeming period.
- Hold the claim until applications open, which CER says is mid to late November 2026.
What this means for you
If you quote a 400 kW roof, the certificate count is a headline number in the quote, so the date, zone and deeming period should be explicit. Use our STC calculator for estimates and see the mid-scale solar STCs pillar, the start date answer and STC trading. To settle the certificates, start trading.