There is a common misreading that selling certificates early locks in value. It does not. The deeming period decides how many STCs a system creates, and it is tied to the install date.
What changes and when
For systems installed in 2026 the deeming period is five years. For 2027 it is four, then it falls by a year each January until it reaches one in 2030. The scheme ends on 31 December 2030. Zone ratings are 1.622, 1.536, 1.382 and 1.185.
On a 6.6 kW system in zone 3, five years gives about 45 STCs. Four years gives about 36. That is a drop of roughly nine certificates per job, which at today’s roughly $38 to $40 spot is a visible cut to the customer’s upfront discount. The full run-through is in what changes in January.
What you can actually act on
- Install date. Jobs installed by 31 December 2026 use the five-year figure. Jobs after use four.
- Lodgement. Get claims in promptly. Cash tied up in a year-end backlog hurts more than a small rate difference.
- Pricing. Quote 2027 jobs on the new STC count, not the old one.
- Pipeline. Pull confirmed installs forward where the customer is ready, but do not rush sites that are not.
A Q4 planning routine
Between now and the end of December, list every signed job and its expected install date. Mark those that can be completed, commissioned and photographed before 31 December, and flag the ones where the customer, the network or the weather could push them into January. For flagged jobs, re-quote on the four-year deeming figure now and explain the difference, so the customer is not surprised later. Then agree with your trader how claims lodged in the last fortnight of December will be handled, because volume is heavy at that time of year.
What this means for installers
Plan your Q4 around documented, complete installs and quick lodgement. Our STC trading page explains how selling works, and the pricing page shows the current rate. Zone-by-zone counts are in the zone rating guide, and the deeming period explainer covers the arithmetic.