Gridly
STC Calculator
Calculate how many Small-scale Technology Certificates your solar system generates and what the government rebate is worth - before you get a quote.
Enter postcode to detect your STC zone
STC price fluctuates - check the Clean Energy Regulator for current price
Used to show cost before vs after rebate
System cost before vs after rebate
What happens if you wait?
The STC scheme reduces by 1/15th each year. Waiting costs you STCs.
| Year | Deeming period | STCs | Rebate value | Loss vs now |
|---|
STC calculations are estimates. The actual number of STCs may vary slightly based on the Clean Energy Regulator's assessment. Always confirm with your installer before purchase.
What are STCs and how do they work?
Small-scale Technology Certificates (STCs) are a federal government incentive under the Renewable Energy Target that reduces the upfront cost of installing solar panels, solar hot water systems, and heat pumps. When you install an eligible system, you are entitled to create a number of STCs based on the system size, your location's solar irradiance, and the remaining years in the STC scheme. These certificates can be sold or assigned to your installer in exchange for a discount on your system price - which is why most Australians never see the STC transaction directly. It is automatically deducted from your quote.
How is the number of STCs calculated?
The formula is: STCs = system size (kW) × zone rating × deeming years. Zone ratings reflect the average solar resource in your location - higher zones generate more electricity per kW of panels, producing more STCs. The deeming period is the number of years remaining until the STC scheme ends in 2030. In 2026, that is four years remaining. As each year passes, the deeming period shortens by one year, which directly reduces the number of STCs a given system generates.
Why does the rebate decrease each year?
The STC scheme is designed to phase out over time. It reduces by 1/15th of its original value each year from 2017 through to 2030, when it ends entirely. This means a 6.6kW system installed in 2026 generates fewer STCs than the same system installed in 2025 - and fewer still than if it had been installed in 2022. Waiting to install solar does cost money through STC reduction. That said, the reduction each year is relatively modest, and other factors - system pricing, tariff changes, your electricity usage - typically have a larger effect on the total value of going solar.
What is the current STC price?
The STC spot price is set by the market and fluctuates. It has typically traded between $35 and $40 in recent years. The default in this calculator is $39, but you can update it with the current market price from the Clean Energy Regulator's REC Registry. Your installer will use a similar market rate when calculating your quote discount - if the price they are applying seems lower than the market rate, it is worth asking about it.
Do installers handle STCs automatically?
In almost all residential solar installations in Australia, yes. Your installer acts as an STC agent - they register the certificates on your behalf and apply the value as an upfront discount to your system cost. You sign an assignment form that transfers the STC entitlement to them. The rebate value you see in this calculator is therefore reflected in the price you pay, not as a separate payment. Use the solar savings calculator to estimate your ongoing annual electricity savings on top of the upfront rebate.