Farms use a lot of electricity, spread across pumps, cooling, sheds and houses, and many have the roof area and the sun to do something about it. They also sit in an awkward spot for certificates. A 60 kW irrigation array is a small-scale system. A 200 kW dairy and packing shed has, until now, been a large-scale system with a different payoff. In October 2026 that line moved. This guide takes the pieces in order.
Which side of the line is your system on
Under the Small-scale Renewable Energy Scheme (SRES), solar systems up to 100 kW create STCs on installation. Above 100 kW, systems were previously limited to large-scale generation certificates (LGCs), created as the system generates. That is changing: systems above 100 kW and up to 1 MW installed from 1 October 2026 create STCs with a fixed five-year deeming period, under 2026 amendments to the regulations. The Clean Energy Regulator says applications open mid to late November 2026. Above 1 MW remains in the LGC world. For the detail, see mid-scale solar and STCs and the 100 kW limit explained.
Zone ratings and the maths
STCs are kW x zone rating x deeming years, rounded down. The zone ratings are 1.622 (zone 1), 1.536 (zone 2), 1.382 (zone 3) and 1.185 (zone 4). Alice Springs is zone 1, Darwin zone 2, Sydney, Brisbane, Perth, Adelaide and Canberra zone 3, and Melbourne, Geelong, Hobart and Launceston zone 4. Rural postcodes follow the CER’s postcode table, so look up the exact postcode.
| Farm system | Zone | Deeming | Calculation | STCs | At about $38.50 |
|---|---|---|---|---|---|
| 30 kW shed array | 3 | 5 (2026) | 30 x 1.382 x 5 | 207 | about $7,970 |
| 99 kW packing shed | 3 | 5 | 99 x 1.382 x 5 | 684 | about $26,300 |
| 200 kW dairy and cool room | 3 | 5 (mid-scale, from 1 Oct 2026) | 200 x 1.382 x 5 | 1,382 | about $53,200 |
| 30 kW, Darwin | 2 | 5 | 30 x 1.536 x 5 | 230 | about $8,850 |
The 200 kW row changes the sums. Before 1 October 2026 the same system would have created LGCs year by year, and LGCs have been roughly $6 to $9 in September 2026 after a low near $4 in February (oversupplied). Compared with that, an up-front STC value is substantial. At the time of writing the STC spot has been roughly $38 to $40.
Off-grid and weak-grid sites
Off-grid systems can create STCs, provided they meet the installation and product rules and are installed by an accredited installer. Rural sites often have weak grids, and a network that limits export, or SWER lines with tight connection limits, can reduce what you can export, but not the STC calculation, which is based on system size and zone and not on how much is exported. Check the network operator’s rules for the connection application, and design the system around on-farm load. A battery is also an option, though the one-per-property rule under the Cheaper Home Batteries Program applies, and eligibility depends on the program’s conditions.
Who signs and who owns
The owner of the system creates the STCs, or assigns them to the installer or an agent for a discount. For a farm, the owner might be an individual, a partnership, a family company or a trust. The signed assignment form needs to match the legal entity, and so do the ABN and the GST details. If the owner is a company, an authorised director signs. If you are not sure who the correct owner is, ask the farm’s accountant before the paperwork is signed. See the STC assignment form.
GST, ABN and invoicing
Many farms are registered for GST and hold an ABN. The sale of STCs is generally a taxable supply, and certificate buyers commonly issue a recipient-created tax invoice (RCTI) on the seller’s behalf where there is an agreement. If the farm assigns its certificates to the installer, the discount and the GST treatment sit in the contract. Check with an accountant for the specific entity. Our explainer on RCTI, GST and ABN for STC payments covers the invoicing mechanics, and GST on STC sales gives the short answer.
From the desk: On a rural job, check the postcode against the CER zone table, not the nearest town. We see rural jobs quoted on a coastal capital’s zone out of habit. A one-step zone difference on a 99 kW system moves the certificate count by about 12% and several thousand dollars.
Hot water, heat pumps and other farm uses
Dairies, packing sheds and farm accommodation use a lot of hot water, and solar hot water and heat pump systems create STCs under the same scheme. For a household-scale unit the STC count is set by the product’s rating and the zone. For larger commercial heat pumps, state schemes may apply: Victoria’s VEU for Victorian farms, and NSW’s Energy Savings Scheme for NSW farms, subject to the eligible activities and method rules. See heat pump STCs explained and VEECs and STCs on the same job.
Evidence in remote locations
The CER’s evidence rules do not relax because the site is remote. Photos, serials and installation records must be captured on the day. Where mobile coverage is poor, make sure photos are saved on the device with the date and location, and that you upload them when you are back in range. See the photo requirements for what to capture.
Timing
The deeming period for small-scale solar steps from 5 to 4 years on 1 January 2027, which cuts the count by 20% on a small-scale system. A 99 kW system in zone 3 drops from 684 to 547 STCs (99 x 1.382 x 4 = 547.3), about $5,300 less. A fixed five-year period for mid-scale systems means that step does not apply to systems over 100 kW. That alone can change which side of the line a farm designs for.
Planning the sequence on a working farm
Farms have seasons. Harvest, calving and irrigation peaks all compete with install dates, and a crew that arrives in the wrong week will lose a day to the farm’s own work. Agree the access plan, the power outage window and the sign-off person before the install week. Then build the certificate steps in: owner details confirmed, photos taken to the checklist, paperwork signed on site. If the decision-maker is not on the property, arrange to sign electronically on the day.
What to do next
- Look up the postcode in the CER zone table and run the numbers in the STC calculator
- Confirm the legal owner, ABN and GST status before any paperwork is signed
- If you are near the 100 kW line, read the mid-scale page before you size the system
- See today’s rate on pricing and how STC trading works
- Browse the glossary for terms