Mid-scale solar: STCs for 100 kW–1 MW systems from 1 October 2026

Commercial solar above 100 kW used to sit outside the small-scale scheme, so businesses had to look at large-scale generation certificates (LGCs) instead. The Renewable Energy (Electricity) Regulations 2001 have been amended so the Small-scale Renewable Energy Scheme now covers 100 kW to 1 MW. This guide covers who qualifies, what the discount looks like, and what to do if your project is already under way.

Which commercial solar systems get STCs from 1 October 2026?

The CER says a mid-scale system is expected to be eligible if it meets all of these, as set out in its transitional guidance:

• its capacity is greater than 100 kW and up to 1 MW
• it is installed on or after 1 October 2026
• its panels, inverters or batteries are on the Clean Energy Council’s approved lists, and it meets Solar Accreditation Australia’s install guidelines
• the installer holds the right accreditation and the work meets electrical safety requirements
• it complies with all planning approvals and network connection requirements
• it meets any other eligibility and evidence rules in the regulations.

The mid-scale rules are an extension of the existing scheme, so the rules for smaller rooftop systems still apply unless the regulations say otherwise. Eligible systems can be grid-connected or stand-alone (off-grid), as long as they meet every requirement.

What counts as “installed”?

A solar system is installed when it is first capable of producing and delivering electricity. In practice, that is the testing and commissioning date on the certificate of electrical compliance, or the equivalent state or territory certificate. Eligibility depends on that date, not on when construction or procurement started.

How many STCs will a mid-scale system earn?

Eligible mid-scale systems get a fixed 5-year deeming period through to 2030. “Deeming” means the CER credits the system with the electricity it is expected to generate over that period, up front. For smaller systems the deeming period shrinks by a year every January. Mid-scale systems keep the fixed 5 years.

The CER has a mid-scale solar STC calculator that it describes as a guide only. We have not found a published step-by-step formula for 100 kW to 1 MW systems, so the example below borrows the formula used for smaller systems: kW × zone rating × deeming years.

Worked example: a 200 kW system (an estimate only)

Assume a 200 kW system, a 5-year deeming period, and the zone ratings from the CER’s postcode zone ratings table. The dollar values use the $33–$38 per certificate the CER says agents usually pay for small-scale certificates. The price for mid-scale certificates may differ.

For the cost side, see how much commercial solar costs and our STC calculator. For typical systems at this scale, see the 200 kW and 500 kW pages.

What if you already have solar on site?

Extending an existing system

An extension can qualify, but only the added capacity earns STCs, using the fixed 5-year deeming. The CER’s example: an existing 80 kW system expanded by 40 kW after commencement may be eligible as a 120 kW mid-scale system, with STCs on the extra 40 kW only. The extension does not have to exceed 100 kW by itself. It does need to:

• form part of the same solar system as the existing one
• be electrically connected to it
• bring the combined capacity above 100 kW and no higher than 1 MW
• meet all the other eligibility requirements.

The 1 MW limit and related systems

The limit looks at the total solar capacity at the site or adjoining sites, and how it is connected and metered. The CER lists electrical configuration, metering, network connection and whether systems are “related” as relevant factors. A single NMI (the National Metering Identifier for your meter) does not by itself decide whether several installations count as one system.

The CER gives two illustrative examples involving an existing accredited large-scale power station:

Existing accredited power stations stay in the Large-scale Renewable Energy Target and can keep creating LGCs, but they need separate metering to do so. If you plan staged builds or several arrays on one site, design the metering and boundaries so each scheme’s capacity is clear. See STCs, LGCs and REGOs explained.

What evidence will the CER want?

You must give the CER written information showing that all Commonwealth, state, territory and local approvals were met, including network connection approval where it applies. Keep these from day one:

• system design documentation
• network connection approvals (where applicable)
• planning and building approvals, and structural engineering reports where applicable
• metering information
• electrical compliance certificates and testing and commissioning records
• panel serial numbers, which are required with the application
• photographs and other installation evidence.

If one network approval covers a staged development, the CER says it will focus on whether the approval covers the specific equipment claiming STCs, and does not currently expect separate approvals just because the project is staged. Our guide to commercial grid connection and export limits covers the network side.

The installer photo rule

For mid-scale systems, accredited installers must keep photographs showing they attended the site for the final stage of installation and commissioning. The photos must:

• be geotagged and time-stamped, and clearly show the installer’s face
• show the installed equipment and the system during testing and commissioning
• line up with the dates on the compliance certificates (if testing runs over several days, take them on the final day).

What should you do now if you are mid-project?

1. Check the commissioning date. It decides eligibility. Ask your installer to confirm in writing when commissioning is planned and that the certificate of electrical compliance will carry that date.
2. Confirm the capacity and site. Add up all solar on the site and adjoining sites, including any accredited power station, and check the total against 1 MW.
3. Get network approval in hand. Ask the network what it needs before you energise, and keep the approval.
4. Check the products and installer. Panels, inverters and batteries must be on the Clean Energy Council’s approved lists. Our accreditation check covers the installer.
5. Decide who claims. Ask whether your installer or an agent will claim the STCs, and how the discount shows on the quote.
6. Keep a records folder. Designs, approvals, serial numbers, commissioning records and the installer photos.
7. Decide on REGOs before you sign. Choosing STCs means no REGO certificates during the deeming period.

Can a project earn both STCs and LGCs or REGOs?

No, not on the same capacity. A solar system cannot create both STCs and LGCs for the same generation capacity. Support for eligible new mid-scale installations comes through the small-scale scheme, not the large-scale one. If you choose STCs, you also cannot create REGO certificates for the deeming period.

This guide is general information, not financial or legal advice. Rules, rebates and prices change, so check the linked sources before you decide. Facts checked 31 October 2026.