The small-scale renewable energy scheme pays for the clean energy a solar system is expected to produce, and it pays all of it up front in the form of STCs. The deeming period is the number of years that the upfront payment covers.
How it works
The number of STCs for a solar system is the system size in kW, multiplied by the zone rating for the postcode, multiplied by the deeming period. For installs in 2026 the deeming period is 5 years. It falls by one year each calendar year, so it is 4 for 2027 and reaches 1 in 2030. The scheme ends on 31 December 2030.
Zone ratings are 1.622, 1.536, 1.382 and 1.185 for zones 1 to 4, which are set by postcode. Most major cities sit in zone 3 or 4; check your own postcode using the Clean Energy Regulator.
An example
A 6.6 kW system in zone 3 in 2026 earns 6.6 x 1.382 x 5 = about 45 STCs. In 2027, at 4 years, it earns about 36 STCs. At roughly $38 to $40 per STC, the certificate value falls from about $1,700 to $1,800, to about $1,370 to $1,440. See the deeming period resource for the full tables.
Why it exists
The scheme was designed to wind down as solar became cheaper and widely adopted. Reducing the deeming period each year is how the government tapers the rebate without a sudden stop.
Common misunderstandings
People sometimes assume the rebate lasts as long as the deeming period or that the panels must be kept for that time. Neither is true. The deeming period is a calculation input for certificates, not a condition on the system. It is also not related to the feed-in tariff, which is a separate arrangement with your retailer.
What this means for installers and homeowners
Installers should reprice each January and tell customers before a cut that the discount falls with the date. Homeowners should expect solar to be cheaper to buy in hardware terms over time, but with a smaller rebate each year. See the schedule by year, the 2027 changes and the STC trading pillar. You can see current rates on our pricing page.