For years the answer was simple: 100 kW. A solar installation up to that size was a small generation unit and created STCs at install. Above it, the owner had to accredit a power station and earn large-scale generation certificates (LGCs) over time. That line has been moved. For systems installed from 1 October 2026, the Small-scale Renewable Energy Scheme extends to 1 MW, with a fixed five-year deeming period. Below 100 kW nothing changes, and above 1 MW remains LGCs. The pillar page is mid-scale solar STCs.
How the 100 kW limit is calculated
The limit applies to the total rated capacity of the solar panels in the system, in kW, added up across all panels on the same installation. It is not the inverter rating and it is not what the array will produce on a given day. Panel ratings come from the approved product list. A system with 250 panels at 400 W is 100 kW. The old rules also carried an annual output test for small units, so confirm the current limits with the Clean Energy Regulator (CER) for edge cases. The question of panels versus inverter is covered in panel size or inverter size.
Is a 99 kW system eligible?
Yes, and so is a 100 kW system. A 99 kW system in zone 3 creates about 684 STCs for a 2026 install (99 x 1.382 x 5), worth roughly $26,000 to $27,000 at $38 to $40 per STC. A 100 kW system creates 691. The full table is in STCs by system size.
99 kW versus 100 kW and the LGC line
The “99 kW trick” came from the cliff at 100 kW: just over it, you lost the upfront STC value and gained an LGC income stream instead. LGCs are created per MWh generated, so the money arrives slowly and depends on the LGC price, which has been low in 2026 (roughly $6 to $9 in September after a low near $4 in February). Designers therefore trimmed commercial systems to 99 kW.
Should you still build to 99 kW?
For installs from 1 October 2026, usually not. A 400 kW system now creates about 2,764 STCs in zone 3 rather than registering as a power station. Size the system to the roof and the load. Splitting a single site into several sub-100 kW systems to dodge rules has always attracted CER attention, and the extension removes the incentive to try. Systems installed before 1 October 2026 follow the old rules, so the install date, not the contract date, decides.
STCs or LGCs above the limit
| Size | Certificate | When the value arrives |
|---|---|---|
| Up to 100 kW | STCs | At install, with the deeming period |
| Above 100 kW to 1 MW, installed from 1 October 2026 | STCs (five-year deeming) | At install |
| Above 1 MW | LGCs | Annually, as you generate |
Applications for the extended band are reported to open mid to late November 2026, so confirm the process with the CER before promising customers a figure.
What this means for installers
Treat 100 kW as the old limit and check the install date before designing. If you are quoting a 150 kW or 400 kW system, read what installers need to know about the expansion and the counts for 200 kW to 1 MW.
For settlement on large jobs see STC trading and pricing.