The STC Clearing House is the Clean Energy Regulator’s backstop market. It buys and sells certificates at one price, $40 excluding GST, and it works as a queue. The words “surplus” and “deficit” describe which side of that queue is longer.
What a surplus means
A surplus is when more STCs have been offered to the Clearing House than buyers are taking up. Sellers lodge certificates onto the transfer list, and they are sold first in, first out as buyers purchase. When the list is long, your certificates sit behind everyone ahead of you, and nobody can say precisely when they will clear.
A surplus tends to appear when certificate creation outpaces what liable buyers are purchasing, and the open market price sits at or just under the ceiling. The regulator reported 6.3 million STCs purchased through the Clearing House in the September 2025 quarter, up from 4.8 million a year earlier, which shows how much volume can run through it. The detail sits in the regulator’s quarterly carbon market reports.
What a deficit means
A deficit is the opposite condition. Buyers (liable electricity retailers or traders) want to buy through the Clearing House, but there are not enough certificates on the transfer list to fill their orders. Sellers are not queuing for long, and open market prices tend to hug the $40 ceiling because certificates are scarce relative to demand.
You will rarely see a long-running deficit in the small-scale scheme because creation has historically kept ahead of retailer demand. Certificates created under the Cheaper Home Batteries Program are bought by the government rather than by retailers, and the regulator describes that purchasing as a way of reducing the effect of battery volumes on the STC market.
Why the price does not move
The $40 figure is set by regulation. Surplus and deficit change the waiting time, not the price. If you want certainty on timing, selling on the open market to a trader avoids the queue. If you only want certainty on price and can wait, the Clearing House gives you that. We compare the two in STC trading price versus the Clearing House.
Where to check the status
The Clean Energy Regulator shows the transfer list position on its website, updated hourly. Look at it before you decide to list certificates. A long queue is the signal to consider a trader instead, and a short one means a Clearing House sale may clear within days.
What this means for installers
Treat the Clearing House as the floor under your price, not your plan A. Check the transfer list, compare it with a trader’s published rate on the pricing page, and read how STC trading works before you commit certificates to the queue. Our guide on how long STC payment should take sets out realistic timelines.