Asking whether your installer is ripping you off on the STC price is a fair thing to wonder, and the good news is you can test it in about five minutes without any inside knowledge. These steps also cover “is my STC discount fair” and “how to check my STC discount”.
The three-step test
1. Is the count right? Use the STC calculator with your postcode and panel capacity. For a 6.6 kW system in zone 3 (Sydney, Brisbane, Perth) installed in 2026 you would expect about 45 STCs. If the quote shows 38, ask why.
2. Is the value per STC reasonable? At the time of writing the market has traded roughly $38 to $40, with the clearing house ceiling at $40. A unit value of $36 to $39 is normal for an installer who sells to a trader. Anything far below that deserves an explanation. See why installers value below spot.
3. Does the total reconcile? Count x value should equal the discount line on the quote. Then confirm the discount reduces the price you pay, as in how the line should appear on an invoice.
Signs the discount is not fair
- The quote only shows “rebate included” with no count or unit value.
- The unit value is $30 or lower when the market is close to $40.
- The STC count is smaller than the calculator and no one can explain it.
- The invoice shows a smaller discount than the quote, with no change in the system.
- You are told the rebate “comes back later”.
Any one of these is a reason to ask. Several together suggest comparing another quote.
What a good answer sounds like
A decent installer will tell you the zone, the deeming year, the STC count and the unit value without hesitating. They will explain that their price reflects what their trader pays them, and they will hold that value until the quote expires. Telling you “the STC price is commercial” and refusing to give a number is not a good answer.
What this means for you
Most disputes about STC value come from a missing number, not a bad actor. Get the count and the unit value on paper, check them against the calculator and keep the quote. If you suspect something more serious, such as an installer who is not accredited or who is asking for payments outside the contract, check their accreditation and read about avoiding STC scams.
See the homeowners guide for more. Installers who want to offer a stronger discount can compare certificate buy rates on the pricing page or start trading.