Understanding what an STC rebate is

Before we jump into the calculation, let’s quickly clarify what the STC rebate is. It’s a federal government incentive designed to make solar more affordable for homes and small businesses across Australia. It’s not a cash-back offer you apply for after the fact. Instead, it works as an upfront discount on the total cost of your solar system.

When you install an eligible solar system, you create Small-scale Technology Certificates (STCs). The number of certificates depends on how much renewable energy your system is expected to produce until 2030, when the scheme is set to end.

Your solar installer will almost always handle the process of claiming and selling these certificates for you, passing the value on as an immediate price reduction on your invoice.

The formula for your STC rebate calculation QLD

To work out how many STCs your new solar system will be eligible for in Queensland, you just need three key pieces of information:

• System Size (kW): The total capacity of your solar panel array.
• Postcode Zone Rating: A rating based on how much sunshine your location receives.
• Deeming Period (Years): The number of years left until the government scheme ends in 2030.

The calculation is:

System Size (kW) x Postcode Zone Rating x Deeming Period = Number of STCs (rounded down)

Once you have the number of STCs, you multiply that by the current market price per certificate to get your final rebate amount.

Amount of Rebate = Number of STCs x Current STC Market Price

Breaking down the calculation components for 2025

Let’s look at each part of the formula in more detail for an installation happening in 2025.

• System Size: This is straightforward—it’s the total kilowatt (kW) rating of your panels. A typical residential system in Queensland is often around 6.6 kW to 10 kW. The larger the system, the more STCs you’ll receive.
• Deeming Period in 2025: The deeming period reduces by one year every 1st of January. For any system installed in 2025, the deeming period is 6 years. This is a crucial point—if you install the same system in 2026, the deeming period will only be 5 years, meaning you’ll get fewer STCs.
• STC Zone Ratings for Queensland Postcodes: Zone 1 (Rating 1.622): Covers most of central and northern Queensland, including areas like Townsville and Rockhampton.
• STC Zone Ratings for Queensland Postcodes: Zone 2 (Rating 1.536): Includes some regional areas.
• STC Zone Ratings for Queensland Postcodes: Zone 3 (Rating 1.382): This is where most of the population lives, covering Brisbane, the Gold Coast, and the Sunshine Coast.
• Current STC Price: The price of an STC fluctuates based on market supply and demand. However, it generally stays within a stable range, typically between $38 and $40 per certificate. For calculations, installers often use a price around $38 or reference the official clearing house price of $40 (ex-GST).

A worked example: 6.6 kW system in Brisbane (2025)

Let’s put it all together with a practical example. Imagine you’re installing a standard 6.6 kW solar system on your home in a Brisbane suburb (postcode 4000) in October 2025.

1. System Size: 6.6 kW

2. Postcode Zone Rating: Brisbane is in Zone 3, which has a rating of 1.382.

3. Deeming Period: For an installation in 2025, this is 6 years.

Calculation for STCs:

6.6 (kW) x 1.382 (Zone Rating) x 6 (Deeming Period) = 54.79

We round this down to the nearest whole number, which gives us 54 STCs.

Calculation for Rebate Value:

Now, we multiply the number of STCs by the current market price. Let’s use an average price of $39 per STC.

54 STCs x $39 = $2,106

So, for a 6.6 kW system installed in Brisbane in 2025, you can expect an upfront discount of around $2,106.

How to claim your STC rebate

The best part about the STC rebate is that you generally don’t have to do any complex paperwork. To be eligible, the key requirements are that your system is under 100 kW and that you use both Clean Energy Council-approved components and, crucially, a Solar Accreditation Australia (SAA) accredited installer.

Your SAA-accredited installer will handle the entire process. They calculate the number of certificates, apply the discount directly to your quote, and then manage the creation and sale of the STCs on your behalf. This makes the whole process simple and ensures you get the savings immediately.

Gigi’s pro tip: Always ask your installer what STC price they have used in your quote. This helps you compare different offers fairly and understand exactly how your discount has been calculated.

Final thoughts

Understanding how your STC rebate is calculated gives you the confidence to know you’re getting a fair deal. The key takeaway is that the rebate is a significant upfront discount, making solar a much more accessible investment for Queensland homeowners. Because the scheme phases out and the number of certificates reduces each year, the sooner you act, the greater your financial benefit will be.

If you’re ready to get a precise quote for your home, I can introduce you to a trusted, SAA-accredited local expert who can provide a detailed breakdown of costs and your specific STC rebate. Just fill out the form below.