Calculate the STC rebate
Type the postcode where the panels will go and the zone fills itself from the Clean Energy Regulator table of 137 postcode ranges, which is built into this page. Change the STC price to match your quote. Nothing you enter leaves your browser.
How the certificate count is made
Small-scale technology certificates are the federal solar rebate. The Clean Energy Regulator counts them with one formula: panel capacity in kW, multiplied by the zone rating for the postcode, multiplied by the deeming period for the install year, rounded down to a whole number. The four zone ratings are 1.622 (Zone 1), 1.536 (Zone 2), 1.382 (Zone 3) and 1.185 (Zone 4). The deeming period is 5 years for a system installed in 2026 and 4 years for one installed in 2027; it falls by a year each 1 January until the scheme ends in 2030.
Each certificate is then sold. The clearing house pays $40 fixed, but almost every installer sells on the open market, where the price traded at $39.90 in the week of 19 to 23 October 2026. This site assumes $39 per certificate to allow for the installer's trading cost. The installer takes the certificates and shows the value as a discount line on the quote, so the number you see is certificates multiplied by whatever price the installer chose.
Worked examples in full
A 6.6 kW system in postcode 2000, Sydney, is in Zone 3 with a rating of 1.382. For a 2026 install: 6.6 x 1.382 x 5 = 45.606, rounded down to 45 certificates. At $39 each the discount is $1,755, or $269 per kW. Installed in 2027 the deeming period is 4 years, so the count is 36 certificates and the discount $1,404: $351 less for the same panels.
A 10 kW system in Melbourne, postcode 3000, is in Zone 4 with a rating of 1.185. In 2026 it earns 59 certificates worth $2,301; in 2027 it earns 47 worth $1,833, a drop of $468.
A 13 kW system in Alice Springs, postcode 0870, is in Zone 1 with a rating of 1.622, the highest, and earns 105 certificates worth $4,095 in 2026. The same 6.6 kW system that earns $1,755 in Sydney earns 39 certificates and $1,521 in Hobart, Zone 4, because the rating is lower.
Certificates and value by size and zone, 2026 installs at $39
Read across for your zone. The dollar figure is certificates multiplied by $39; multiply the certificate count by your own price if the quote uses a different one. A 6.6 kW system is worth $2,067 in Zone 1 and $1,521 in Zone 4, a spread of $546 for identical hardware.
| Size | Zone 1 (1.622) | Zone 2 (1.536) | Zone 3 (1.382) | Zone 4 (1.185) |
|---|---|---|---|---|
| 3 kW | 24 ($936) | 23 ($897) | 20 ($780) | 17 ($663) |
| 5 kW | 40 ($1,560) | 38 ($1,482) | 34 ($1,326) | 29 ($1,131) |
| 6.6 kW | 53 ($2,067) | 50 ($1,950) | 45 ($1,755) | 39 ($1,521) |
| 8 kW | 64 ($2,496) | 61 ($2,379) | 55 ($2,145) | 47 ($1,833) |
| 10 kW | 81 ($3,159) | 76 ($2,964) | 69 ($2,691) | 59 ($2,301) |
| 13 kW | 105 ($4,095) | 99 ($3,861) | 89 ($3,471) | 77 ($3,003) |
The 1 January 2027 step
The install date decides the deeming period, not the date you sign. A system switched on and signed off by 31 December 2026 is deemed for 5 years; one installed on 1 January 2027 or later is deemed for 4 years, so every certificate count drops by one fifth, 20 per cent, before rounding. In Zone 3 that is $351 on 6.6 kW and $546 on 10 kW. The step is smaller than the price difference between a dear quote and a fair one, so it is not a reason to accept a poor quote in December; it is a reason to ask any installer quoting for a December install what happens to the price if the job slips into January.
| Size | 2026 (5 years) | 2027 (4 years) | Difference |
|---|---|---|---|
| 3 kW | 20 ($780) | 16 ($624) | $156 |
| 5 kW | 34 ($1,326) | 27 ($1,053) | $273 |
| 6.6 kW | 45 ($1,755) | 36 ($1,404) | $351 |
| 8 kW | 55 ($2,145) | 44 ($1,716) | $429 |
| 10 kW | 69 ($2,691) | 55 ($2,145) | $546 |
| 13 kW | 89 ($3,471) | 71 ($2,769) | $702 |
Reading the STC line on a quote
Most quotes show a system price, a line called STC discount, rebate or government incentive, and a price after it. For 6.6 kW in Zone 3 that line should be close to $1,755 at $39, $1,800 if the installer uses the $40 clearing house price, and $1,575 if it uses $35. A line under $1,580, more than 10 per cent below our figure, means the installer is pricing the certificates low or counting fewer panels than the quote names; ask which. A line well above $1,800 usually means the kW on the quote is larger than the panels listed, which is worth checking against the panel count and wattage.
The STC line is not a cash payment to you. The installer owns the certificates once you sign the assignment form and recovers the money by selling them; what matters is the price after the discount, which the quote check compares with this month's index and the solar panel cost pages put in context by city and size. State rebates, such as Victoria's $1,400, come off after the STC line and are covered on the solar rebates page.
Which zone your postcode is in
The Clean Energy Regulator publishes 137 postcode ranges that cover every Australian postcode from 0000 to 9999. The capitals fall as follows: Sydney (2000), Brisbane (4000), Perth (6000), Adelaide (5000) and Canberra (2600) are Zone 3; Melbourne (3000) and Hobart (7000) are Zone 4; Darwin (0800) is Zone 2. Zone 1, the highest rating, is inland: Alice Springs (0870), the Pilbara and Kimberley ranges from 6642, and a handful of western Queensland postcodes such as 4829. Cairns (4870) and Townsville (4810) sit inside the 4830 to 5431 range, which is Zone 3, despite the sun: the ratings are set from the regulator's radiation model, not from a map of the tropics.
Zone 2 covers most of inland New South Wales, Queensland, South Australia and the Western Australian wheatbelt and goldfields, for example 2356 to 2357, 2385 to 2389, 5432 to 5450 and 6574 to 6602. The calculator above walks the full table, so a postcode on a zone boundary is read exactly as the regulator reads it. The rating table has not changed since 1 January 2020.
Assumptions and sources in plain words
The zone ratings and the postcode ranges are transcribed from the Clean Energy Regulator document "Postcode zone ratings and zones for solar (photovoltaic) systems", as of 1 January 2020, downloaded on 27 October 2026 and checked for 137 contiguous ranges and four ratings. The deeming periods (5 years in 2026, 4 in 2027) are from the regulator's page on calculating certificate entitlements, read the same day. The $39 price is this site's assumption: the open market traded at $39.90 in the week of 19 to 23 October 2026 and the clearing house pays $40, and the installer carries a trading cost. The calculator rounds down after multiplying, as the regulator does, and treats the kW you type as DC panel capacity, which is what the regulator counts; the inverter rating is irrelevant. Systems above 100 kW use a different scheme. The calculator runs in your browser, sends nothing to a server and stores nothing.
STC rebate questions
How many STCs does a 6.6kW solar system get?
45 certificates in Zone 3 (Sydney, Brisbane, Perth, Adelaide and Canberra) for a 2026 install, worth $1,755 at $39 each; 39 certificates worth $1,521 in Zone 4 (Melbourne and Hobart). In 2027 the Zone 3 count falls to 36, worth $1,404.
How is the STC rebate calculated?
45 certificates for 6.6 kW in Zone 3 comes from 6.6 x 1.382 x 5 = 45.606, rounded down. The formula is kW x zone rating x deeming years, and the dollar value is certificates x the price the installer gets, assumed here to be $39.
What is an STC worth in October 2026?
$39 is the assumption on this site. The open market traded at $39.90 in the week of 19 to 23 October 2026, the clearing house pays a fixed $40, and the installer carries a trading cost, so quotes commonly price certificates between $35 and $40.
How much does the STC rebate drop in 2027?
$351 on a 6.6 kW system in Zone 3: $1,755 in 2026 against $1,404 in 2027, because deeming falls from 5 to 4 years on 1 January 2027. On 10 kW in Zone 4 the drop is $468.
Which STC zone is my postcode in?
4 zones cover every postcode: Sydney, Brisbane, Perth, Adelaide and Canberra are Zone 3 (rating 1.382), Melbourne and Hobart are Zone 4 (1.185), Darwin is Zone 2 (1.536) and Alice Springs is Zone 1 (1.622). Type your postcode into the calculator and it reads the regulator's table of 137 ranges.
Do I get the STC money as cash?
$0 arrives as cash in almost every case. The installer takes the certificates by assignment and shows their value, about $1,755 for 6.6 kW in Zone 3, as a discount on the quote. You can keep the certificates and sell them yourself, but then you pay the full price upfront and wait for the clearing house.