The shortening deeming period is not a policy surprise or a market effect. It is arithmetic built into the scheme’s design.
The logic: count the years left
The Renewable Energy Target and its small-scale scheme (SRES) were legislated to run to 2030. STCs are created for the electricity a system is deemed to generate between installation and the end of the scheme. Since 2017, that period has been one year shorter each year, so that it reaches 1 year in 2030, the last year, and zero afterwards.
In 2026 there are five years until the end of 2030 on the counting convention used, so the period is 5. In 2027 it is 4, and so on to 1 in 2030. This has the effect of making the scheme’s cost to electricity customers and retailers taper rather than stop sharply.
What it does to the numbers
For a 6.6 kW zone 3 system the fall is a fixed 9 STCs per year in 2026 to 2030, because 6.6 x 1.382 is about 9.12 per deeming year. At roughly $38 to $40 an STC at the time of writing, each January step costs about $340 to $360 in discount on that job. See the full schedule.
The fall does not depend on the market. STC prices can move up or down, but the period steps down every 1 January on a fixed schedule.
Is there a catch?
The decline applies to the certificates, not to the system’s savings. A household still saves on its bills for the life of the panels. What disappears is the upfront incentive, and the payback gets longer as it does. See the solar rebate drops every year and will the rebate end in 2030.
What this means for installers
Demand pulls forward. Expect more enquiries in November and December as customers understand the January step. Be careful about promises: a quote signed in December is not guaranteed the current year’s period unless the install is completed and commissioned in that year. For the mechanics, see what is a deeming period and the pillar.
See what changes in January 2027 for the next step. Today’s buy rate is on pricing, and start trading opens an account.