The 100 kW limit used to be the line that separated the two certificate schemes. For installs before 1 October 2026, crossing it meant a rooftop system stopped being a small generation unit eligible for STCs and became a power station that creates LGCs. From 1 October 2026, systems above 100 kW and up to 1 MW create STCs too, with a fixed five-year deeming period, so the line now sits at 1 MW. See mid-scale solar STCs.
The small-scale tests
A system qualifies as a small generation unit if it is 100 kW or less in capacity and its annual output is under 250 MWh. Both conditions matter. A 95 kW system in a very sunny location with high yield could in theory approach the generation limit, so check the numbers. See LGC vs STC for the general comparison.
What STCs look like at 99 kW
For a 2026 install in zone 3, a 99 kW system earns 99 x 1.382 x 5 = 684 STCs. At roughly $38 to $40 at the time of writing, that is about $26,000 to $27,000 upfront. In 2027 the deeming period drops to four years, so the same system earns 547, a drop of 137 certificates.
What happens above 100 kW
From 1 October 2026, up to 1 MW, the system creates STCs: 120 kW in zone 3 is 120 x 1.382 x 5 = 829 STCs, about $31,500 to $33,000 at the time of writing. The Clean Energy Regulator says applications open mid to late November 2026.
Above 1 MW, or for systems above 100 kW installed before 1 October 2026, the owner must apply for accreditation as a power station, install the right metering, and create LGCs after generation. The value is spread over years and priced at spot, roughly $6 to $9 in September 2026. See what is an LGC.
Design considerations
- Check the capacity definition, and how it applies to your design, before you finalise.
- Size to the customer’s load. Up to 1 MW the certificate is an upfront STC either way; the deeming period is the difference (shortening for small-scale, fixed at five years for mid-scale).
- Be careful about splitting one site into multiple small systems. The regulator treats artificial splitting seriously.
From the desk: the old habit of designing to 99 kW should be retired for installs from 1 October 2026. Choose the size the site needs, state the install date on the quote, and note that mid-scale claims cannot be lodged until applications open.
What this means for installers
Decide the pathway at design stage, not at claim stage. For small-scale commercial jobs, see STC trading, pricing and the resources hub. The wider context is in commercial solar rebate in Australia.