STCs or REGO certificates: choosing for a 100kW to 1MW solar system

In short

• From 1 October 2026, a new solar system of 100kW to 1MW can choose STCs or REGO certificates.
• STCs give one upfront discount, worked out on 5 years of power. REGO certificates are earned as the system makes power, with no end date.
• You can't have both for the same years, so choose before you apply. For most businesses, STCs are worth far more today.

Until 1 October 2026, a business solar system over 100kW couldn't get the upfront STC discount. Now systems up to 1MW can. The Clean Energy Regulator (CER) says owners of these "mid-scale" systems can choose between the STC discount and REGO certificates. The choice matters because, in the CER's words, if you choose STCs "you will not be able to create REGO certificates for the deeming period."

What are STCs and REGO certificates?

STCs (small-scale technology certificates) are the government's upfront solar discount. A system earns them when it's installed, based on its size, its location and a set number of years of power. You can create them yourself, or assign them to a registered agent, usually through your installer. The CER says that if you assign them, "you might be able to receive an upfront discount on the cost of your system." The full detail is in STCs for business and the 1MW change.

REGO certificates come from the Renewable Electricity Guarantee of Origin scheme. The CER issues one certificate for each megawatt-hour (MWh) of renewable power a registered system makes. They are earned over time, as power is made, not upfront. The CER says businesses "can use REGO certificates as evidence of renewable electricity use", and can trade them or retire them.

Does my system qualify?

The 100kW to 1MW range counts all the solar on your site, not only the new system. The rules add together the new system, any related solar already on the site, and any related accredited power stations. The CER's guidance says that if existing and new solar on a site or adjoining sites together go over 1MW, the new system isn't eligible.

If you're adding to an existing system, only the new part counts. The CER's own example: an 80kW system expanded by 40kW gets the 5-year STCs on the extra 40kW only.

The system also needs:

• panels, inverters and any batteries on the Clean Energy Council's list of approved components
• installation by an accredited installer, to Solar Accreditation Australia's install guidelines
• evidence that planning and approval requirements have been met, plus geotagged photos from the installer

Can a new 100kW to 1MW system choose the large-scale scheme and its LGCs instead? No. The CER says support for new mid-scale systems "is provided through the SRES rather than the LRET". LGCs remain for existing accredited systems and for new systems over 1MW.

How much is each option worth?

Here's a worked example for a 500kW system. These figures are examples for the sums, not a quote.

STCs, upfront:

• The number of STCs is kW × your area's rating × 5 years. Your area's rating is set by the CER: 1.382 in zone 3 (Perth, Brisbane, Sydney, Adelaide), 1.185 in zone 4 (Melbourne).
• Zone 3: 500 × 1.382 × 5 = 3,455 STCs. At $39.85 each, that is about $137,700.
• Zone 4: 500 × 1.185 × 5 = 2,962 STCs, or about $118,000.

The CER's mid-scale STC calculator gives the exact number for your postcode. The value on your quote depends on the price your installer or agent pays, so read the STC line.

REGO certificates, over time:

• Using YourHome's Perth figure of about 4.4 kWh a day per kW, 500kW makes about 803 MWh a year. That is about 803 REGO certificates a year.
• The CER doesn't publish a REGO price, so no one can say what they're worth yet. For a sense of scale only: LGCs, a similar certificate from the scheme that ends in 2030, were $7 at the end of June 2026 and $8.50 on 14 August 2026. At those prices, 5 years of certificates (about 4,015) would come to roughly $28,000 to $34,000.

In plain words: at today's prices, the STC discount is worth several times more than 5 years of certificates, and you get it upfront. REGO certificates may be worth more to a business that needs to show it uses renewable power.

When might REGO make sense?

• You need proof of renewable power. The CER says REGO certificates can be used as evidence of renewable electricity use, including in emissions reporting. A business with renewable energy targets may value that more than the market price.
• Certificates beyond 2030. The CER says the Renewable Energy Target ends on 31 December 2030, but "the REGO will continue indefinitely."

If you choose STCs, can you switch to REGO once the 5 years are over? The CER only rules out REGO "for the deeming period", which suggests you could. But it hasn't said so directly, and it warns that "certificate eligibility under one scheme may affect eligibility under another". Ask your installer, or the CER, before you count on it.

How do you claim each one?

STCs:

• They must be created within 12 months of installation.
• The CER expects applications for mid-scale systems to open in mid to late November 2026, with assessment after that. A system installed in October is still inside the 12 months.
• Most businesses assign them to a registered agent, usually through the installer, and get the value as a discount on the invoice.

REGO certificates:

• First you enrol (the CER allows up to 6 weeks to assess it), then register the system as a facility (up to 90 days).
• Certificates only count from the date the facility is registered, and must be claimed within 12 months of the power being made. The CER suggests starting the application 10 to 12 weeks before the system starts running.
• You report meter data to create them.
• Current fees: $490 to enrol, $50 to register a system under 10 MW, and 8 cents per certificate. The CER expects fees to rise over time.

What to ask your installer

• Does all the solar on my site, old and new, come to 1MW or less?
• If I'm extending an existing system, how many kW of it will earn STCs?
• Is the STC discount on my quote based on the 5-year rule for mid-scale systems?
• Who will create the STCs, and when will the discount show on my invoice?
• Would REGO certificates suit my business better, and can I move to them after 5 years?

The choice only matters once you know your system's size, and that depends on your power use. Send a bill and an accredited installer prepares a costed proposal with the STC discount worked out for your site. It is free, with no obligation. To spread the cost, see commercial solar finance.