The STC Solar Discount Explained: How It Cuts Your Price

If you've looked at a solar quote, you've already met the STC discount — you just might not have noticed it. The federal Small-scale Renewable Energy Scheme (SRES) is the single biggest reason a rooftop solar system costs what it does, and it's one of the few solar incentives that is genuinely national: it applies the same way whether you're in Perth, Penrith or Pialba. Here's how it actually works, and why the discount gets a little smaller each year.

What an STC is, and how it lowers your price

STC stands for Small-scale Technology Certificate. When you install an eligible rooftop solar system (or a heat-pump/solar hot water unit), the system is credited with a number of certificates based on how much clean energy it's expected to generate over its remaining deeming period. Those certificates have a dollar value and can be traded. In practice, you almost never touch them yourself — your installer handles the paperwork and assigns the certificates to themselves in exchange for an upfront discount on your invoice.

This matters for how you read a quote. The headline prices installers advertise are nearly always the price after STCs have been applied. In our national figures, an indicative installed price after STCs looks like this:

System size	Indicative price after STCs
6.6 kW	$4,000 – $6,500
10 kW	$6,000 – $10,000
13.2 kW	$7,500 – $13,000

These are broad national ranges — your actual price depends on your roof, switchboard, and installer. The point is that the STC discount is already inside those numbers, not something you claim separately afterwards.

Why the discount shrinks over time

The number of certificates a system earns is tied to a "deeming period" — effectively the number of years left until the scheme ends. The SRES is legislated to phase out at the end of 2030. Each 1 January, the deeming period drops by one year, so an identical system installed later earns fewer certificates and attracts a smaller upfront discount.

This is a slow, predictable grind, not a cliff. We mention it because it's easy to be pressured by a "prices going up" line. The shrinkage is gradual and has been happening for years. It's real, but it rarely justifies rushing a decision you're not otherwise ready to make.

The big change for commercial solar

There's a significant shift for larger systems. Since 1 October 2026, the SRES threshold has risen from 100 kW to 1 MW. That means commercial solar systems between 100 kW and 1 MW — the "missing middle" of warehouses, farms, factories, schools and shopping centres — now create STCs upfront at installation instead of relying on large-scale certificates (LGCs). The Clean Energy Regulator estimates this cuts upfront cost by roughly 20% for those systems.

For context: systems under 100 kW were already on STCs, and systems over 1 MW still use LGCs. This is a regulated change, so if you're weighing a mid-sized commercial install, confirm the current commencement details and certificate treatment before you bank on the saving.

Where STCs don't help you — the honest catch

The STC discount lowers the purchase price. It does nothing for the thing that actually determines whether solar pays: how much of your generation you use yourself versus export. With feed-in tariffs now typically in the range of just 3–10 c/kWh and trending down for years, exported power earns very little. A big system bought at a big STC discount still underperforms if most of its output is sold back to the grid for pocket change.

So the discount is a genuine benefit — but it's a benefit on the wrong half of the equation if your usage pattern doesn't match solar generation. For some households and businesses, a smaller system that you self-consume heavily beats a larger, more heavily-discounted one you mostly export. That's exactly the kind of trade-off worth modelling against your actual bill before you commit.

How to check the discount is really in your quote

• Ask the installer to show the STC value as a separate line, then confirm the price you pay is after that deduction.
• Check the system is installed by a CEC-accredited installer with compliant components — non-compliant systems don't earn certificates.
• Don't treat the STC saving as a reason to oversize. Size to your consumption first.
• For commercial systems, confirm whether yours falls under the under-100 kW, 100 kW–1 MW, or over-1 MW banding — it changes the certificate type entirely.

We don't sell or install a single panel, so we've got no reason to talk the STC discount up or hurry you along. Our only job is to tell you whether — once the certificates, your usage and your feed-in rate are all on the table — solar actually stacks up for you. Sometimes the honest answer is a smaller system, or not yet.

Figures in this guide are current at the date of publication and indicative only — rebate and certificate values change over time (federal battery certificates step down each January and July), and state schemes are amended often. Confirm the current numbers for your situation before you commit. This is general information, not personal financial advice.