Small-Scale Technology Certificates (STCs) Explained

Most Australians who install solar panels receive a significant upfront discount without fully understanding why. That discount comes from the federal government's Small-Scale Renewable Energy Scheme (SRES), which creates tradeable certificates called STCs (Small-Scale Technology Certificates) for eligible systems.

What Is an STC?

An STC represents one megawatt-hour (MWh) of renewable electricity that a solar or hot water system is expected to generate or displace over its lifetime (up to 2030). The number of STCs a system creates depends on:

• System size: A larger solar system creates more STCs
• Location (installation zone): Sunnier locations create more STCs per kW (4 zones across Australia)
• Deemed years remaining: STCs were originally calculated to 2031; as 2030 approaches, the multiplier reduces (currently ~4 deeming years)

STC Zones in Australia

Australia is divided into 4 STC zones based on solar irradiance:

• Zone 1 (highest): Darwin, far north QLD — best STC value
• Zone 2: Perth, Brisbane, much of QLD
• Zone 3: Adelaide, Sydney, regional NSW and SA
• Zone 4 (lowest): Melbourne, Hobart, ACT

Adelaide (Zone 3) generates approximately 35–38 STCs per kW of installed solar.

What STCs Are Worth

STCs trade on an open market at prices that fluctuate. The maximum face value is $40/STC (set by the Renewable Energy Target), but market prices currently trade at $35–$39/STC.

For a typical 6.6 kW system in Adelaide (Zone 3) with ~4 deeming years:

• STCs created: ~87 STCs
• At $37/STC: ~$3,219 value
• At $39/STC: ~$3,393 value

This is why you see solar systems advertised "after STCs" — the installer assigns the STCs to an STC agent, who pays them for the certificates, and that value is passed on as a point-of-sale discount to you.

Do I Need to Do Anything?

For most homeowners, no. When you sign the installation contract, you assign your right to create STCs to the installer. They handle all paperwork, registration, and STC creation through the Renewable Energy Certificate Registry. You receive the discount automatically.

Alternatively, you can create and sell STCs yourself — but this requires registration with the CER and is rarely worth the administrative effort for a small residential system.

When Do STCs Phase Out?

The SRES and STCs are scheduled to end on 31 December 2030. Each year until then, the number of deeming years (and therefore STCs created per kW) reduces by one. This means:

• Installing now creates more STCs than waiting 2–3 years
• From 2031, residential solar will have no federal rebate unless the scheme is extended

The phaseout is gradual, but there is a genuine incentive to install before 2030 to maximise STC value.