LGC vs STC for a 100 kW solar system: which is better in 2026

Written and checked by the Energy Merchants desk · Reviewed 2 October 2026

The 100 kW line has long been the fork in the road for commercial solar. Below it, a system creates small-scale technology certificates (STCs) up front. Above it, it used to create large-scale generation certificates (LGCs) over time. In 2026 that line moved, and a lot of older advice on this question is now out of date.

What changed on 1 October 2026

The Small-scale Renewable Energy Scheme now extends to mid-scale solar. Systems above 100 kW and up to 1 MW installed from 1 October 2026 create STCs with a fixed five-year deeming period, under amended Renewable Energy (Electricity) Regulations. The Clean Energy Regulator says applications open mid to late November 2026. Below 100 kW nothing changes. Above 1 MW remains LGCs. Our mid-scale solar STC guide covers the detail.

STC and LGC compared

A worked example

Take a 99 kW system in a zone 3 postcode such as Sydney or Brisbane, installed in 2026. At a zone rating of 1.382 and a five-year deeming period, the deemed output is 99 x 1.382 x 5, which is about 684 STCs. At $38 to $40 that is roughly $26,000 to $27,400, in a single claim. The figure is illustrative; check the STC calculator for your own numbers.

Now a 101 kW system installed after 1 October 2026 in the same zone. With the five-year fixed period it works out at about 697 STCs, so the 101 kW system is not penalised against the 99 kW system, subject to the CER’s application process. Before the change, the same 101 kW system would have been an LGC producer, earning perhaps 140 MWh a year (an assumption, site dependent) at an LGC price of $6 to $9, which is roughly $840 to $1,260 a year. The old cliff was steep; the new rules largely remove it.

99 kW vs 101 kW: what to ask now

• Is the system installed on or after 1 October 2026? If not, check which pathway applies.
• Have you confirmed the CER’s application window, which opens mid to late November 2026?
• Are the panels, inverters and installer eligible for the pathway?

Do not design around the old 100 kW cliff without checking the current rules.

Selling LGCs: broker or direct

If you do own a generator above 1 MW, you have LGCs to sell, and you can sell them through a broker, directly to a retailer or other liable entity, or through a trader. A broker can find a buyer and manage the transfer, usually for a fee or a spread. A direct sale can suit a larger volume but takes more effort. LGCs have been oversupplied and cheap in 2026, so fees matter more than usual. Ask for net dollars per LGC and who holds the certificates in the meantime. See how to compare STC traders for questions that apply here too.

What this means for design

For years, installers sized commercial systems just under 100 kW to keep the upfront STC payment. With the extension to mid-scale solar, the choice of size can follow the site’s load and roof rather than the certificate cliff. That is a significant change in how a quote can be built. It also means that installers who have always quoted 99 kW will need to review their templates, and that customers who were told to cap at 99 kW should be asked to revisit the brief. Remember that the CER application window opens in mid to late November 2026, so claims on systems installed from 1 October 2026 will follow that process, and confirm timing before promising settlement dates. For commercial customers weighing ownership against a PPA, see commercial solar PPA vs buying outright.

A fair verdict

For systems at or below 100 kW, STCs. For systems above 100 kW up to 1 MW from 1 October 2026, STCs under the extended scheme. Above 1 MW, LGCs. Check the LGC pillar and the CER for rule changes. If you want STC rates for a commercial job, see /pricing/ or start trading.