Three of the questions people type into search are really one: why is there a $40 STC price ceiling, is the Clearing House price fixed, and what does that mean for the market price. They share the same answer.
The $40 is set in regulation
The STC Clearing House sells at a fixed price of $40 excluding GST. The Clean Energy Regulator confirms the price is set by regulation and is not negotiated. The Clearing House is a backstop built so that buyers and sellers always have a transaction available at a known price.
Why a ceiling exists
The logic is cost control and certainty. Small-scale certificates are created by households and small businesses, a market no regulator can forecast to the certificate. If supply ran short, a pure market price could spike and pass straight through to electricity bills. The $40 Clearing House price caps that exposure. For sellers it provides something equally useful: a price at which certificates can always be sold, even if the wait is uncertain.
That fixed price has been in place since the scheme split from the old REC arrangements on 1 January 2011. You can read the background in the history of the STC scheme.
Why the market price sits just under $40
Liable entities, usually electricity retailers, need STCs to meet their obligations. They can buy at $40 from the Clearing House, so a rational buyer will not pay more than $40 on the open market. Sellers who cannot wait for the transfer list accept slightly less for faster payment. The result is a market that clusters just under the ceiling. At the time of writing the STC spot market has been roughly $38 to $40.
Fixed price, uncertain timing
The ceiling is a price guarantee, not a payment guarantee. The Clearing House sells in order from the transfer list, so the wait depends on the queue, as we explain in how long the Clearing House takes. That timing risk is what a trader’s discount from $40 pays for.
What changes the gap
The gap between the spot price and $40 widens when certificate supply is heavy and the queue is long. It narrows when supply tightens. Lower scheme volumes towards 2030 may tighten it, but that is a forecast and not a promise. Our piece on what an STC is worth in 2026 tracks the current position.
What this means for installers
Build quotes around the rate you will actually receive. Use $40 as the ceiling in your model and the daily trader rate as the working number. For help with the arithmetic see the STC formula explained, and for the wider picture start at how STC trading works.