For years the 100 kW line decided everything: at or under it, you got STCs at the point of sale; above it, you waited for LGCs created on metered generation. That boundary has now moved.
The current position
| System size (solar PV) | Certificates, at the time of writing |
|---|---|
| Up to 100 kW | STCs, with a deeming period that shortens each year (5 years for 2026 installs) |
| Above 100 kW to 1 MW, installed from 1 October 2026 | STCs, fixed five-year deeming period |
| Above 1 MW | LGCs |
The regulations were amended in 2026 and CER says applications for the mid-scale STCs open mid to late November 2026. Our mid-scale solar STCs pillar has the detail.
Should you build under 100 kW to get STCs?
Until 1 October 2026 the answer was often yes: STCs paid upfront were worth far more than a few years of LGCs. Now the answer is almost always no, for three reasons.
- The array size should follow the load, roof and economics. Cutting 20 kW from a good design to hit 99.9 kW costs you energy for decades.
- A system above 100 kW and up to 1 MW can create STCs from 1 October 2026, so the certificate cliff has gone.
- The deeming period for sub-100 kW systems is declining (4 years for 2027, down to 1 in 2030) while the mid-scale period is fixed at five. A system just over 100 kW can actually earn a longer deeming period than one just under it in 2027 and later. Check what applies to the date you install.
Do not split one site into multiple “99 kW” systems. The rules look at the total onsite capacity, and artificial splitting invites compliance action.
Worked comparison
Take a 120 kW system in zone 3 (rating 1.382), installed after 1 October 2026: 120 x 1.382 x 5 = 829 STCs, worth roughly $31,500 to $33,000 at $38 to $40. The same site capped at 99 kW in 2027 with a four-year period: 99 x 1.382 x 4 = 547 STCs, worth roughly $20,800 to $21,900. Run your own site through the STC calculator.
Existing systems and older jobs
None of this changes what has already been installed. A system above 100 kW commissioned before 1 October 2026 stays on the LGC pathway it was already on, and a small-scale system keeps its STCs. The new band applies by installation date, so confirm the date that counts for your project in the CER’s transitional guidance.
What this means for you
Design to the load, then pick the pathway. The LGC pillar explains large-scale certificates, pricing shows what STCs currently settle for, and STC trading explains how claims are processed. The LGC versus STC answer is a good second read.