STC Solar Rebates Explained: What They Are and How to Claim Them

Small-scale Technology Certificates — STCs — are the way the federal government reduces the upfront cost of residential solar in Australia. Most installers fold the rebate into your quote without explaining it, which leaves customers wondering what they’re actually signing when they accept the system. This post explains exactly how the STC scheme works, how many STCs your system earns, and what the paperwork looks like in practice.

What STCs are and why they exist

STCs were introduced as part of the federal Renewable Energy Target (RET). The idea is that every kilowatt of residential renewable energy capacity generates a tradeable certificate, and the electricity retailers (who have a legislated obligation to source a percentage of their supply from renewables) buy those certificates. The certificate market funds the rebate.

For solar specifically, your system earns a number of STCs at installation, based on:

• System capacity in kilowatts (kW).
• Your installation zone — Australia is divided into four zones based on solar resource. All of South East Queensland sits in Zone 3.
• The current deeming period — the number of years’ worth of generation the scheme credits you for upfront. This is the part that steps down on a fixed schedule.

The deeming period — and why January 1 matters

The deeming period is the part of the STC calculation that reduces every year on 1 January. When the scheme was at its most generous, the deeming period was 15 years. It currently sits lower than that and steps down one year on every 1 January, with the scheme winding up entirely on 1 January 2031.

What this means in practice:

• A system installed on 31 December earns more STCs than the same system installed on 1 January the next year. Same hardware, different deeming period.
• The rebate is locked in at install-completion date, not contract date. If you sign a contract in mid-December and install slips into January, you fall into the next deeming period. The ACCC has flagged the contract-vs-completion confusion as a misleading- conduct vector under ACL § 18 — any installer quoting a December rebate for a January install is misrepresenting the scheme.
• The schedule is public and fixed. No surprises; we use the deeming period that applies on your install date.

How the per-system STC count is calculated

The formula the Clean Energy Regulator uses is, simplified:

STCs = system capacity (kW) × zone multiplier × deeming period (years)

For QLD (Zone 3), the zone multiplier is currently 1.382. So a 6.6 kW system installed in Zone 3 today earns:

6.6 × 1.382 × deeming-period years = STC count

The STC count is then multiplied by the current STC spot price (set by market trading; we confirm the price on the day at quote time) to produce the rebate dollar amount. Because the spot price varies week to week, we re-confirm it during the quote acceptance period rather than freezing a stale number.

We don’t publish a generic dollar figure here for a reason: the ACCC’s Australian Consumer Law guidance flags lumped “STC saves you $X” claims as misleading conduct unless the figure is substantiated per customer for the specific system, install date, and spot price. The substantiated figure lives in your quote PDF.

How the rebate is applied

You don’t see a separate STC cheque. The rebate is applied as a point-of-sale discount on the upfront cost of your system. The mechanism is:

1. You sign an STC assignment form when you accept the quote. This delegates ownership of the STCs to us (the installer).
2. At install completion, the Certificate of Electrical Compliance triggers the STC creation. We register the system on the Clean Energy Regulator’s portal and create the STCs against your install address.
3. We sell the STCs on the open market and apply the proceeds as a discount on your invoice. You see the discount line-by- line on your quote — gross system cost, STC rebate, final price.

You never handle a certificate, never lodge anything with the Regulator, and never wait for a cheque. The discount is in your final invoice.

What about the CHBP (battery rebate)?

The Cheaper Home Batteries Program uses the same STC machinery, just applied to batteries instead of panels. If you’re installing solar and a battery together, you’ll earn STCs for both — itemised separately on your quote, with the deeming-period factor and the CHBP-tier factor each calculated for their respective install dates.

We wrote a separate post on the CHBP specifically — see How the Cheaper Home Batteries Program Works in Queensland.

Getting your numbers

If you’d like to know how many STCs your specific roof and address would generate, get a free quote. We model the exact number using the deeming period that applies on your install date, the current STC spot price, and your system size.