STC 1MW Commercial Solar Quotes: What Changes Oct 2026

In short: from 1 October 2026, systems between 100 kW and 1 MW move onto upfront STCs instead of annual LGCs – the regulations registered on 17 September 2026. For anyone quoting STC 1 MW commercial solar jobs, the practical work is not understanding the policy (we covered that separately); it is re-sizing designs that were clipped at 99 kW, handling contracts that straddle the start date, and rewriting the incentive line on every proposal template between 100 kW and 1 MW.

The 99 kW Design Ceiling Is Gone – What to Re-size

For years, the rational move on a commercial roof that could hold 130 kW was to quote 99 kW. Crossing 100 kW meant giving up the upfront rebate, registering as a power station, and collecting LGCs one year at a time against a price outlook that has kept falling. From 1 October, that trade-off mostly disappears for anything up to 1 MW, so the first job on any live pipeline is going back through quotes that were deliberately undersized and asking whether the roof actually supports more.

That re-sizing touches more than the panel count. A jump from 99 kW to, say, 300 kW usually means a different inverter tier, a heavier DC/AC cabling run, and – because most networks apply a different connection-approval tier above certain export thresholds – a fresh look at the DNSP application before you commit to a number in a proposal. None of that is new engineering; it is work that installers simply stopped doing above 100 kW because the incentive maths never justified it. Check switchboard and main incomer capacity, re-confirm the export limit the network will actually approve, and only then lock the system size the incentive line will be built around. A site that genuinely tops out at 105–110 kW may still be simpler to leave at 99 kW for now, rather than take on a size that barely clears the threshold for a marginal STC gain.

Quoting Jobs That Straddle 1 October

The rule keys off install date, not the date a customer signs. A 250 kW system installed in September earns STCs on the first 100 kW and LGCs on the balance under the pre-expansion rules; the same job installed in October earns a whole-system upfront STC discount instead. A contract signed today for a November install is eligible for the expanded rules – install date is the whole test, not when the project was designed, procured or contracted, and there is no transitional relief for jobs that straddle the 1 October line.

There is a second timing gap worth flagging to customers directly: the government’s own guidance says applications for mid-scale STCs are not expected to open until mid-to-late November 2026, even though the eligibility window starts 1 October. A system installed on day one of the new rules can still be weeks away from an installer actually being able to create and sell its certificates. If a proposal assumes the STC discount lands at settlement, say so explicitly, or model it as a delayed credit instead of an upfront one for early October installs.

For the quote itself, two things belong in the fine print rather than left implied. First, a validity clause that ties the quoted incentive value to the system being installed on or after 1 October – installed meaning tested and commissioned, not designed or delivered. Slip to September and the quote reverts to the old rules (STCs to 100 kW, LGCs above) and needs re-pricing, not honouring at the higher figure. Second, a line stating that the site’s total solar capacity stays at or under 1 MW. The regulations test the new array together with related arrays and any accredited power station on the same or an adjoining site, so the first megawatt is what carries the upfront certificates and anything above it goes back to annual LGCs.

STC Upfront vs LGC Annual Revenue: The Maths for 250 kW and 500 kW

Using the figures from the STC expansion guide: at a zone 3 rating (1.382, most east-coast capitals) and a fixed 5-year deeming period to 2030, a 250 kW system installed under the expanded rules creates roughly 1,727 STCs (250 × 1.382 × 5, rounded down). At $39.40 per certificate, that is about $68,000 upfront. A 500 kW system creates roughly 3,455 STCs, worth about $136,000 upfront.

Now compare that with staying on LGCs. Assume the same 1,400 kWh per installed kW per year that the LGC guide uses for its 250 kW example (350 MWh/year, so 350 LGCs/year under the 1-certificate-per-MWh rule), and the August 2026 spot price of $7.75/LGC. A 250 kW system earns about $2,700 in year one; a 500 kW system (700 MWh/year, 700 LGCs) earns about $5,400.

Even holding the LGC price flat for five years – generous, since the sibling LGC guide describes a market still trending down toward 2030 – the cumulative LGC total is about 20% of the upfront STC figure on both system sizes. Put another way, a 250 kW system would need roughly 25 years of LGC revenue at today’s price to match the upfront STC discount, and the LRET stops issuing LGCs at all after 2030. That is the arithmetic behind why the expanded rules favour the upfront certificate for almost any new mid-scale project that can be installed after the start date, and it is worth walking a customer through directly when they ask why the quote changed.

What Still Applies Above 100 kW

Moving onto STCs removes the power-station accreditation and revenue-grade generation metering that the LGC route requires – that overhead was always the bigger deterrent for mid-scale systems than the certificate maths itself, and it goes away under the new rules. What does not go away is ordinary grid metering: a commercial system between 100 kW and 1 MW still needs a DNSP-compliant import/export meter for its network connection, the same as it would today, regardless of which certificate scheme prices it.

On accreditation, mid-scale systems sit inside the existing small-scale installer and product accreditation rules – a Clean Energy Council–accredited installer, panels and inverters on the approved products list – plus the usual state and territory electrical safety requirements, rather than a separate regime. The registered regulations add three conditions specific to mid-scale systems: confirmation that all Commonwealth government requirements have been met, written evidence to the Clean Energy Regulator that every Commonwealth, state, territory and local planning and approval requirement (network connection approvals included) has been satisfied, and a matching written statement from the installer. One requirement is relaxed rather than added: the accredited-designer requirement does not apply to mid-scale units, and AS 4777 can be recorded as not applicable where it does not cover the inverter.

How to Present the Incentive on a Proposal

Three things belong on the incentive line for any 100 kW–1 MW quote. A clear line item stating which scheme priced the discount – the mid-scale STC regime or the LGC path – rather than a single unlabelled rebate figure. An assumption note underneath it giving the certificate price, the deeming period or LGC-price assumption used, and the zone rating, so anyone reviewing the number later can see exactly what it rests on. And a validity clause, as above, tying the figure to the install date and to the site’s total capacity, rather than presenting it as locked in.

A workspace that keeps STC and LGC pricing regime-aware makes this easier to do consistently: Amperage prices the mid-scale rules off a project’s install date, keeps the switch visible so a job can be quoted the old way, names the scheme on the proposal, and swaps the LGC stream out automatically when mid-scale STCs apply, so the two schemes are never both quoted on the same capacity by accident.

Checklist: Updating Templates and Pricing Before 1 October

• Re-run any live quote between 100 kW and 1 MW that was capped at 99 kW purely for the incentive, and check the roof, inverter tier and DNSP export limit actually support the larger size.
• Add an install-date-conditional validity clause, and a line capping the site’s total capacity at 1 MW, to every proposal template that quotes an incentive above 100 kW.
• Split the incentive assumption note out from the headline discount figure so the certificate price, deeming years and zone rating are visible, not buried in a total.
• For jobs installing in the first weeks after 1 October, flag the likely gap between eligibility starting and STC applications opening (expected mid-to-late November) so the customer is not surprised by a delayed credit.
• Remove any hard-coded 100 kW cap from pricing spreadsheets or template logic that puts everything above 100 kW onto LGCs, and replace it with the 1 MW ceiling, conditional on install date.
• Update metering and accreditation line items on any 100 kW–1 MW template to cover the three mid-scale compliance conditions (Commonwealth requirements met, written planning/approval evidence, installer statement) and the accredited-designer exemption.

Where to Go From Here

The full policy background – what was announced, what it is worth, and what the registered regulations settled – is covered in full in the STC expansion guide. For the certificate maths on systems that stay on the annual path, or that sit above 1 MW, see the LGC guide. Every current scheme, price and stacking rule lives on the solar incentives hub.

STC calculator – run a 100 kW to 1 MW system →

LGC calculator – compare against annual certificates →