How Do STCs Work? A Plain-English Guide for Sydney Homeowners
How Do STCs Work? A Plain-English Guide for Sydney Homeowners
How Do STCs Work? A Plain-English Guide for Sydney Homeowners
If you’ve been getting solar quotes in Sydney, you’ve probably seen “STC discount” listed as a line item that brings the headline price down. It’s one of the most misunderstood parts of buying solar in Australia, so here’s how Small-scale Technology Certificates (STCs) actually work, without the jargon.
What is an STC?
An STC is a tradeable certificate created under the federal Small-scale Renewable Energy Scheme (SRES). When you install an eligible solar (or eligible battery, in some cases) system, the system is deemed to generate a certain amount of renewable energy over its remaining lifetime up to 2030, when the scheme is due to wind down. That deemed generation is converted into a number of STCs.
Each STC represents 1 megawatt-hour of that deemed generation. The number of certificates your system creates depends on three things: the size of the system in kilowatts, the postcode it’s installed in (Sydney sits in a specific “zone rating” that affects the sum), and the year of installation, because the multiplier used in the calculation steps down annually as the scheme approaches its 2030 end date.
Why does the number of STCs matter to you?
STCs have a market value — they’re bought and sold, and the price moves with supply and demand, roughly within a band set by the scheme’s clearing-house mechanism. Most installers, including Superb Solar, handle this for you: rather than you receiving the certificates and selling them yourself, you assign them to the installer or their agent in exchange for an upfront discount on your invoice. That’s the “STC discount” you see quoted.
Because the certificate price moves with the market, the exact dollar value of that discount isn’t fixed — it’s worth asking your installer which STC price they’ve used in your quote and when it was last updated, rather than assuming the number on a quote from a few months ago still applies.
Why the number of STCs is shrinking each year
The SRES multiplier reduces every calendar year on the way to zero in 2030. In practical terms, this means the same size system installed today creates fewer certificates than it would have a few years ago, and will create fewer again next year. This is a deliberate, scheduled phase-down — not a sign that solar is becoming less viable, just that the certificate scheme is winding down as the technology matures. It’s a reasonable factor to weigh if you’re deciding whether to install this year or wait, since deferring doesn’t improve your certificate outcome.
How this plays out on a real quote
When you get a quote, look for these details so you can actually compare offers on a like-for-like basis:
- The system size in kW used to calculate the STC count
- The zone rating applied (Sydney has its own rating under the scheme)
- Whether the STC discount has already been deducted from the headline price, or whether it’s listed separately
- Whether the installer is registered to create and assign STCs on your behalf through the Clean Energy Regulator’s systems
A legitimate STC discount should be traceable — your installer should be able to explain, in plain terms, the inputs they used. If a quote just states a round discount figure with no breakdown, it’s worth asking for the calculation behind it.
STCs and battery storage
Some battery systems can also be eligible for a separate scheme (and some states run their own battery incentive programs on top of the federal one). These are assessed differently to solar panel STCs, and eligibility depends on the specific battery model and your location, so it’s worth confirming battery-specific eligibility directly rather than assuming it works the same way as the panel discount.
The bottom line
STCs are a real, government-backed mechanism that lowers the upfront cost of going solar — but the exact value depends on system size, location, the year you install, and current certificate market pricing, so it will vary quote to quote and year to year. The most useful thing you can do as a homeowner is ask your installer to show the inputs behind the number, rather than taking the discount figure at face value.
If you’d like a quote with the STC calculation explained line by line, Superb Solar can walk you through it for your specific Sydney address — call 1300 371 883 or email info@superbsolar.com.au.
