Most solar quotes show a price “after STC rebate” or list the STC value as a line item. It is not a separate government payment. It is the installer’s estimate of what your certificates are worth, passed on to you as a lower price in exchange for your signed assignment.
The three numbers to look for
- STC count. This is the system size in kilowatts multiplied by the zone rating and the deeming period, rounded down. For a 2026 install, the deeming period is five years.
- Value per STC. At the time of writing the market has been roughly $38 to $40, with a clearing house ceiling of $40. An installer using $30 is keeping a margin.
- Total discount. Count times value.
A 6.6 kW system in a zone rated 1.382 earns 45 STCs. At $38 that is $1,710, and at $40 it is $1,800. The 6.6 kW worked example has other zones.
Why quotes differ
Installers carry the risk of rejection, pay for compliance and wait for settlement, so most keep a small margin between the market and the discount they apply. That is fair. A big gap is a question worth asking. Another reason is timing. A quote can assume an install date, and if the system is registered after a deeming period change on 1 January, the count falls.
Questions to put to your installer
- How many STCs are you applying, and at what price each?
- What happens if the install slips into the new year?
- Who is responsible if the claim is rejected?
From the desk: compare final out-of-pocket prices, not the size of the discount. A bigger discount on a higher base price is not a better deal.
A quick sense-check
Take the system size on the quote, multiply by your zone rating and by five for a 2026 install, and round down. If the STC count on the quote is within a certificate or two of that, the maths is sound. Then divide the dollar discount by the count. If the answer is well under the market price, you have found the installer’s margin. A few dollars a certificate is normal. Twenty is worth a conversation.
What this means for you
You can rely on the solar rebate calculator to cross-check the STC count in two minutes. For more on how the scheme works, see the resources hub and STC trading.