Australia's STC Rebate, Explained: The Formula, the Discount and the Deadline
The federal solar rebate is not a cheque from Canberra – it is a tradeable certificate scheme that shows up as a discount on your quote. Here is exactly how STCs are calculated in 2026, what they are worth, how the new battery rebate stacks on top, and why the whole thing shrinks every January until it ends in 2030.
When an installer quotes you a 6.6 kW system for thousands of dollars less than the hardware and labour should cost, the gap is almost always Small-scale Technology Certificates, or STCs. They are the mechanism behind the Small-scale Renewable Energy Scheme (SRES), the federal incentive that has driven Australia's world-leading rooftop solar uptake. Understanding the formula lets you sanity-check any quote in about thirty seconds.
How STCs actually work
Under the SRES, an eligible solar system is deemed to generate a certain amount of renewable electricity over the remaining life of the scheme, and one certificate is created for each megawatt-hour of that deemed output. Electricity retailers are legally required to buy and surrender these certificates each year, which gives them a market value. You are technically the owner of the certificates your system creates – but nearly everyone signs them over to the installer in exchange for an upfront discount.
STCs = system size (kW) × zone rating × deeming years remaining (rounded down)Two of those three inputs are outside your control, and one of them – the deeming period – falls every year.
Zone ratings: where you live sets the multiplier
Australia is divided into four solar zones based on expected generation. Sunnier zones create more certificates per kilowatt:
| Zone | Rating (approx.) | Example areas |
|---|---|---|
| Zone 1 | ~1.622 | Far north and central inland Australia |
| Zone 2 | ~1.536 | Much of inland NSW, QLD, WA |
| Zone 3 | ~1.382 | Sydney, Brisbane, Perth, Adelaide, Canberra |
| Zone 4 | ~1.185 | Melbourne, Tasmania, coastal Victoria |
Check your postcode's zone on the Clean Energy Regulator's tables – a few areas sit in surprising zones, and the ratings above are approximate figures worth verifying for your address.
Deeming years: the clock that runs out in 2030
The scheme ends on 31 December 2030, and the deeming period is simply the number of calendar years left, including the year of installation. Install in 2026 and your system is deemed for 5 years (2026–2030). Every 1 January the number drops by one: 4 years in 2027, 3 in 2028, and so on, until the rebate reaches zero after 2030.
What a certificate is worth
STCs trade on an open market, and prices have floated in roughly the $35–$40 band in recent years. The STC clearing house offers a fixed $40 price (excluding GST) which acts as an effective ceiling, but selling there can involve queues, so most certificates clear slightly below it – commonly around $37–$39. Installers quote using their expected sale price, which is one reason identical systems can carry slightly different discounts.
Worked example: 6.6 kW in Zone 3, installed in 2026
6.6 kW × 1.382 × 5 years = 45.6 → 45 STCs
45 × $38 ≈ $1,710 discount (range ≈ $1,575–$1,800 at $35–$40)That is the number that should be visible, itemised, on your quote. If a quote shows a much larger federal rebate for a 6.6 kW system in 2026, ask what deeming period and certificate price they used. You can model the full purchase, rebate and payback for your own postcode with our Australia solar calculator.
Check any quote in under a minute. Enter your system size and postcode to see the expected STC discount, generation and payback for 2026 installation.
Open the Australia solar calculator →Why it appears as a point-of-sale discount
You could register and sell your own certificates, but the paperwork, registry fees and market timing make it rarely worthwhile for a household. Instead, virtually every installer asks you to sign an assignment form transferring the STCs to them (or their agent), and in exchange the certificate value is deducted from your invoice on the spot. The practical consequences: the advertised price of solar in Australia is almost always the after-STC price, the system must be installed and designed by Clean Energy Council (now Solar Accreditation Australia) accredited people using approved panels and inverters to create certificates at all, and the installer – not you – carries the certificate price risk.
The new federal battery rebate
Since 1 July 2025, the Cheaper Home Batteries Program has extended STCs to home battery storage. At launch it cut roughly 30% off the installed cost of a typical battery, calculated per kilowatt-hour of usable capacity. The support declines over time, and from changes slated for 1 May 2026 the per-kWh certificate factor steps down further (with full support focused on the first ~14 kWh of capacity and reduced rates above that). As a rough 2026 guide, expect support in the region of $250–$310 per usable kWh depending on install date – but this program has already changed once, so verify current factors before signing. Eligibility requires the battery to be connected to new or existing solar and installed by accredited installers; like solar STCs, it arrives as a point-of-sale discount. Whether a battery makes financial sense on top of the rebate depends on your tariff and usage – test it in our battery payback calculator.
State top-ups exist too
Several states stack their own incentives on top of the federal scheme: Victoria offers interest-free solar and battery loans through Solar Victoria, and other states and territories run rotating rebate or loan programs. These change often and usually have income or property-value caps, so check your state program's current status rather than relying on installer marketing.
Feed-in tariffs are low – self-use is where the money is
The generous feed-in tariffs of the 2010s are gone. Most retailers now pay around 3–8 cents per kWh for exports, while grid electricity typically costs 25–40 c/kWh. Every kilowatt-hour you use yourself is therefore worth four to ten times what you get for exporting it. Run appliances during the day, consider load shifting before oversizing, and read our self-consumption vs export guide before deciding on system size. Our solar savings calculator lets you test different self-use percentages.
The honest declining-rebate math
What waiting a year costs. Because deeming falls by one year every January, the rebate shrinks by one deeming-year's worth annually. In 2026 that is one-fifth of the remaining rebate: our 6.6 kW Zone 3 example drops from ~45 STCs (~$1,710) to ~36 STCs (~$1,368) in 2027 – roughly $340 lost by waiting. The percentage bite grows each year (a quarter in 2027, a third in 2028), but note the flip side: panel prices have historically fallen too, so the rebate decline is an argument against indefinite delay, not proof that this year is automatically the cheapest.
Common mistakes
- Calling it a rebate you apply for. There is no application and no cheque; the value arrives as a discount because you assign the certificates to your installer. If it is not itemised on the quote, ask why.
- Using last year's deeming period. Online calculators and old blog posts often assume 6 or more years. In 2026 it is 5, and quotes based on stale numbers overstate the discount.
- Assuming the $40 clearing house price. Most certificates sell on the open market slightly below the cap; a quote priced at $40 flat is optimistic, not wrong, but ask.
- Ignoring accreditation requirements. Unaccredited installers or unapproved hardware create zero certificates. A suspiciously cheap quote that skips accreditation forfeits the entire rebate.
- Sizing for export income. At 3–8c feed-in, exports barely move the needle. Size for your daytime consumption and let self-use drive the payback.
Frequently asked questions
How many STCs does a 6.6 kW system get in 2026?
In Zone 3 (Sydney, Brisbane, Perth, Adelaide), about 45 certificates: 6.6 kW multiplied by the ~1.382 zone rating and the 5 deeming years remaining, rounded down. At typical certificate prices of $35–$40 that is roughly $1,600–$1,800 off the installed price. Zone 1 systems earn more, Zone 4 less.
Do I need to apply for the STC rebate?
No. You sign a form assigning your certificates to the installer, who deducts their value from your invoice at the point of sale. The quoted price of solar in Australia is almost always the after-STC price. Selling certificates yourself is possible but rarely worth the paperwork for a household.
Is there a federal rebate for home batteries?
Yes. The Cheaper Home Batteries Program, running since 1 July 2025, extends STCs to battery storage and initially cut around 30% off installed cost. The support factor steps down over time, with further reductions from May 2026, so verify the current per-kWh figure before signing a contract.
Should I wait for cheaper panels or install before the rebate shrinks?
The rebate falls by one deeming-year each January – about 20% of its remaining value if you wait from 2026 to 2027, and a growing share each year until it ends after 2030. Hardware prices may keep falling, but they now need to drop several hundred dollars a year on a typical system just to offset the shrinking certificate count.