2026 is the last year of the 5 year deeming period before it starts to step down. That makes 2026 the best year left for certificate volume per system, and it is worth knowing how big the effect is.
2026 numbers
The formula is kW x zone rating x 5, rounded down.
| System | Zone 1 | Zone 2 | Zone 3 | Zone 4 |
|---|---|---|---|---|
| 6.6 kW | 53 | 50 | 45 | 39 |
| 10 kW | 81 | 76 | 69 | 59 |
At roughly $38 per certificate at the time of writing, a 10 kW zone 3 system carries about $2,620 in certificate value. Market prices move, so recalculate when you quote.
What counts as a 2026 install
The deeming period is based on the installation date, not the date of the contract or the quote. A system energised in December 2026 gets 5 years; one in January 2027 gets 4. Customers who sign in November but see the install slip into the new year lose a fifth of the certificates.
Batteries are separate
If you are adding a battery, use the battery STC calculator guide. The 2026 factor is 6.8 per kWh of usable capacity, stepping down to 5.7 on 1 January 2027 and 5.2 on 1 July 2027 (the factor now steps every six months to 2030).
What this means for you
The best use of a calculator is a comparison: this year against next year, one zone against another. Energy Merchants shows its live buy rate on the pricing page, and the deeming period and zone ratings guide covers the schedule through to 2030. See also the STC trading pillar.
Prices move, so treat any number here as a snapshot and check the live figure before you quote a job.
Because 2026 is the final 5 year deeming year, expect busy installer calendars through the last quarter. Confirm equipment availability and distributor sign-off early, and keep paperwork ready so claims lodge the day the system is energised.
The mix of solar and battery work in 2026 also changes the picture. A customer who adds a battery gets a second set of certificates, with a factor of 6.8 per kWh this year, so the combined upfront discount in 2026 is the largest it will be. Mention both to customers considering a staged install, and explain what they give up by waiting until January.