For years, commercial solar sales had a fault line at 100 kW. Under it, the customer got an up-front STC discount. Over it, the customer got LGCs that arrived slowly and, in a market that has since collapsed, not very valuably. That fault line has moved. For systems installed from 1 October 2026, the small-scale scheme extends up to 1 MW, and the commercial pitch changes with it.
This guide is for installers and retailers selling to businesses. It lays out the three certificate routes, works the numbers on typical system sizes, and covers the traps in quoting. It reflects the CER’s position that applications for mid-scale STCs open mid to late November 2026, so confirm final eligibility conditions on the CER site before you promise a figure. The pillar page mid-scale solar STCs tracks the detail.
The three routes
| System size and date | Certificate | When the value arrives | Deeming |
|---|---|---|---|
| Up to 100 kW | STCs | Up front, from the claim | Five years for 2026 installs, stepping down yearly |
| Above 100 kW to 1 MW, installed from 1 October 2026 | STCs | Up front, from the claim | Fixed five years |
| Above 100 kW installed before 1 October 2026, or above 1 MW | LGCs | Over time, as generation is measured | Not applicable |
Below 100 kW nothing has changed. Above 1 MW remains LGCs.
Worked numbers
The STC count is system size in kW x the postcode zone rating x the deeming years, rounded down. Zone ratings are 1.622, 1.536, 1.382 and 1.185. Sydney, Brisbane, Perth and Adelaide are zone 3 at 1.382, and Melbourne and Hobart are zone 4 at 1.185. STC spot has been roughly $38 to $40.
| System | Zone | Calculation | STCs | Value at $39 |
|---|---|---|---|---|
| 90 kW, 2026 install | 3 | 90 x 1.382 x 5 | 621 | $24,219 |
| 250 kW, from 1 October 2026 | 3 | 250 x 1.382 x 5 | 1,727 | $67,353 |
| 500 kW, from 1 October 2026 | 4 | 500 x 1.185 x 5 | 2,962 | $115,518 |
| 900 kW, from 1 October 2026 | 3 | 900 x 1.382 x 5 | 6,219 | $242,541 |
Now compare the LGC route. A 1.5 MW rooftop in a zone 3 city generates roughly 1.5 x 1,400 = 2,100 MWh a year. At the roughly $6 to $9 range seen in September 2026, that is $12,600 to $18,900 a year. LGCs are oversupplied and cheap at the time of writing, and the scheme ends in 2030.
By comparison, a 900 kW system earning $242,541 in STCs up front is a different financial proposition. That is the gap this policy created, and it explains why customers will ask about the cap.
Selling it honestly
Be clear about the date
The STC route applies to systems installed from 1 October 2026. A system installed on 30 September is on the old rules. Put the installation date in the contract and understand how the CER treats a project that straddles the date. Check the CER’s guidance before you promise a customer a certificate type.
Do not split artificially
A customer with a 1.4 MW roof does not become a mid-scale customer by being sold two 700 kW systems on one site. The regulator assesses how generating systems are defined, and a split designed only to dodge a cap can be challenged. Design for the load and the roof, then see which route applies. If the customer’s load supports a 950 kW system, that is a legitimate design.
Model the certificate line conservatively
STC value at $39 is a spot-based figure. Put the assumed price and date on the quote and show the sensitivity. On the 250 kW example above, each $1 on the price is $1,727. If the customer’s finance depends on the certificate value, it should be locked early. A trader that locks the rate when a complete claim is lodged limits the exposure to the period before lodgement.
Do not oversell LGCs
If your system sits on the LGC side, show the revenue as a modest line. At roughly $6 to $9, a 2,100 MWh system makes about $13,000 to $19,000 a year, and the certificates also need ongoing registry work. See how to create LGCs for the steps, and why LGC prices are falling for the reasoning.
From the desk: the commercial customer will ask who owns the certificates. Write it into the contract. If you are taking the STCs as a discount, the customer must see the dollar figure on the quote and the assignment form. If the customer keeps the certificates, they need the registry account and an agent. Ambiguity here is expensive in both directions.
Cash flow on bigger jobs
A 500 kW job in a zone 4 postcode creates 2,962 STCs, about $115,500. Ten such jobs a quarter is $1.15 million of certificate value. If your trader pays in 20 days, you are funding that value for most of the quarter. If it pays in 24 hours, the exposure is a day. Faster payment matters more as ticket sizes rise. See installer cash flow problems.
Compliance on mid-scale systems
Mid-scale systems are larger and more complex than residential ones, and the evidence expected will be set by the CER. Expect requirements for design documents, product approvals, accredited installers, photos and serial numbers. Until the application process opens, keep records to the same standard as a residential claim and add commissioning data. See how STC audits work and STC photo requirements.
A commercial quoting checklist
- Which route does the system fall into, and on what date?
- What is the system size, and does it sit under 100 kW, between 100 kW and 1 MW, or above?
- What are the zone rating and the STC count?
- What price and date is the quote assuming, and what is the sensitivity?
- Who owns the certificates and how are they transferred?
- How will the first claim be pre-checked?
Talking to the customer about 1 MW
When a customer’s load could support a system larger than 1 MW, explain the trade-offs plainly. A system at or below the cap earns up-front STCs on a fixed five-year deeming period. A system above the cap earns LGCs over time, at a price that is cheap at the moment. The customer’s decision should be driven by their energy needs, roof space and finance, not by the certificate rule. If a design lands naturally under the cap, the STC route is a bonus. If it does not, say so honestly and show the LGC line as the modest stream it is. Our answers on commercial solar rebates in 2026 and the 100 kW STC limit give customers a plain-language version.
What to do next
- Read mid-scale solar STCs and the commercial solar over 100 kW answer.
- Check the LGC pillar at /lgcs/ and the LGC side in LGC price forecast 2027.
- Use the STC calculator for smaller systems and look at our pricing page for the daily rate.
- Talk to the desk about large claims: start trading.