STCs or LGCs? There are two tests, and most people check one.
Australian commercial solar sits either side of a boundary that determines how you get paid for generating. Everyone knows the 100 kW capacity figure. Fewer know that a system also has to produce less than 250 MWh a year to stay small-scale — and that failing either test moves you onto an entirely different scheme with different administration, different timing and different risk.
Reviewed by the Mission Green commercial team · Updated August 2026
Small-scale needs
both boxes ticked.
Capacity is the famous one. Output is the one that catches people.
The Clean Energy Regulator sets out that a rooftop solar system is small-scale — and therefore creates STCs — when it has a capacity of 100 kW or less, has a total annual electricity output of less than 250 MWh, lists its panels and inverter on the Clean Energy Council approved product lists, and meets the relevant Australian and New Zealand standards.
If the system has a larger capacity or a larger electricity output, the CER states it may be classed as a large-scale system instead.
Read that again, because the word doing the work is and. A 99 kW system is not automatically small-scale. In a high-irradiance location with a well-oriented array, 99 kW can push past 250 MWh a year, and the output test decides it — not the nameplate figure on the quote.
The same generation,
two very different deals.
One arrives as a discount you never touch. The other is a job you take on.
Deemed and upfront
Certificates for future years are calculated at installation and normally assigned to your installer, who applies them as a discount on the invoice. No registration, no metering obligation, no ongoing admin.
Metered and annual
One certificate per megawatt hour actually generated, created year after year. You must be accredited as a power station and meet the metering and reporting obligations that come with it.
Certainty vs upside
STCs are simple and immediate. LGCs can be worth more over a system's life, but you carry the price, metering and compliance risk to get it.
The CER notes the usual price paid for an STC by agents is in the range of $33 to $38, while being explicit that it does not set the certificate price and does not get involved in disputes between owners and agents. That is a useful reality check on any quote that assumes a specific certificate value: the number is a market price, not a government rate.
Why so many systems
are exactly 99 kW.
A boundary in a scheme becomes a boundary on rooftops.
Once a threshold carries this much administrative weight, it stops being a technical detail and starts shaping what gets built. A business that could use 160 kW is regularly quoted 99 kW, because the alternative is registering as a power station and running certificate compliance for the next couple of decades.
That is a rational decision by the installer and often the right one for the customer. It is also a system sized to a rule rather than to a load, and it is worth knowing that is what happened — particularly if your consumption has grown since, or you are now looking at electrification, refrigeration load or fleet charging that the original sizing never contemplated.
This is the distortion the announced 1 MW change is aimed at. From 1 October 2026, subject to regulations being in place, the CER says systems between 100 kW and 1 MW should be able to create STCs — which would let most commercial rooftops be sized to consumption rather than to a certificate boundary.
So what should
your business actually do?
Short version.
Check the output test, not just the capacity. Ask your installer for the modelled annual generation in MWh and confirm it sits under 250 for a small-scale system. A quote that only quotes kW has answered half the question.
Size to your interval data first, then see which scheme you land in. Doing it the other way round is how a business ends up with a system that fits a rule and not a building.
Treat certificate value in a quote as a market estimate. The CER is explicit that it does not set the price. If a proposal's payback depends on a particular certificate value, ask what the payback looks like if that value moves.
If you are between 100 kW and 1 MW, watch the October date. That band is the one the announced change is aimed at, and the mechanism is not yet in regulation.
STCs, LGCs and the 100 kW line:
your questions, answered.
STCs are small-scale technology certificates, deemed for future years and normally assigned to your installer so they arrive as an upfront discount on the invoice. LGCs are large-scale generation certificates, created one per megawatt hour of metered generation each year, and they require accreditation as a power station along with the metering and reporting that goes with it.
Under the Clean Energy Regulator's current rules, a system with a capacity of 100 kW or less and a total annual electricity output of less than 250 MWh, using Clean Energy Council listed panels and inverter and meeting the relevant Australian and New Zealand standards. Both the capacity and the output test have to be satisfied.
Because capacity and output are not the same thing. A 99 kW array in a high-irradiance location with good orientation can generate more than 250 MWh in a year, and that would put it outside the small-scale definition despite the nameplate figure. Ask for the modelled annual generation, not just the system size.
It depends on what constrains you. Under the threshold is simpler and puts money in on day one. Over it can be worth more across the system's life but requires you to register as a power station and carry the metering, compliance and certificate price risk. Neither is universally better, and the right answer follows from your consumption and your appetite for administration.
The Clean Energy Regulator announced on 5 August 2026 that eligibility is intended to extend to systems between 100 kW and 1 MW installed from 1 October 2026, subject to regulations being in place. Until those regulations are made, the existing thresholds apply.
The Clean Energy Regulator notes the usual price paid by agents is $33 to $38, and is explicit that it does not set the price and does not mediate disputes between owners and agents. It is a market price, so treat any quote that depends on a precise certificate value as carrying that risk.
Where these figures come from.
Clean Energy Regulator, for both the current eligibility tests and the announced change.