In short
- A Perth factory on day shifts should expect a commercial solar payback of around two to two and a half years in 2026, the shortest of the capitals, because Perth gets the most sun of any city here.
- A commercial system in Perth earns nothing for exports: the state buyback scheme covers only small residential and similar systems, so the whole case is self-use.
- Perth sits on its own grid, run by Western Power, and above 30 kVA the connection goes through a non-standard process.
For a Perth manufacturer, commercial solar in 2026 pays back in roughly two to two and a half years on a weekday-shift site, and under two years on two shifts, with nothing counted for exports. More sun than any other capital does the work. This page covers what is specific to Perth. The shift-pattern sums, the 1 MW STC change and the tax position are on solar for manufacturing, and the city as a whole is on commercial solar Perth.
| Quick facts | Manufacturing solar in Perth |
|---|---|
| Network | Western Power, on the South West Interconnected System |
| STC zone | Zone 3, rating 1.382 |
| State incentive | None; the buyback scheme excludes commercial systems |
| Example payback | 1.9 to 2.3 years at 100kW, with exports at zero |
| What to send | one recent bill; we get the interval data from it |
What's different in Perth
1. A separate grid and a 30 kVA line
Perth is on the South West Interconnected System, which Western Power operates on its own; nothing about the connection process matches the eastern states. The line that matters is 30 kVA of inverter capacity. Below it, a system goes through Western Power's basic embedded generator process. Above it, the connection is non-standard: a technical assessment of the feeder the site sits on, application fees to match, and a longer approval.
- Up to 30 kVA: the basic process.
- Around 100kW: a non-standard connection with a feeder assessment. Export limiting is common on constrained parts of the network, and a Perth factory can be built at zero export if the load suits, which it often does.
- Above 100kW: the same non-standard process with a fuller assessment. Since 1 October 2026 a 100kW to 1MW system can take the upfront STC discount (mid-scale rules), which suits the large sheds at Kwinana, Welshpool and Canning Vale, as long as the plant uses the output.
2. The STC zone: Zone 3
Perth postcodes sit in STC Zone 3, rating 1.382. A 100kW system installed in 2026 earns 100 × 1.382 × 5 = 691 certificates see the postcode zone table on the Clean Energy Regulator page. With the strongest sun of the capitals on top, the upfront discount and the annual saving are both at the good end of the range.
3. No state rebate, and no export income
Western Australia has no rebate for commercial solar; the federal STC discount is the only upfront reduction. Exports are the weak point: the Distributed Energy Buyback Scheme covers only residential, not-for-profit and educational customers with systems of 5kW or less, so a commercial system gets nothing from it. Any payment for a factory's exports comes down to its retail contract, and it is usually small or nothing. A Perth system earns its money by covering the factory's own load, which is why the example below counts exports at zero.
4. Perth's factories, and the sun
General knowledge, not a measurement: Perth's heavy industry is at Kwinana and Rockingham to the south, with lighter manufacturing, fabrication and food at Welshpool, Kewdale, Canning Vale, Malaga and Wangara. Mining services workshops are a Perth speciality, and many run day shifts with heavy daytime draw from welding, machining and compressed air, which is close to the ideal solar load. Sites are three-phase with a demand charge, often set by an afternoon peak in summer.
A Perth roof makes about 1,600 kWh per kW a year, the most of any city on this site and roughly 28% more than Melbourne. A 100kW system here makes what a 128kW system makes in Melbourne. See demand charges for whether the panels touch the peak.
What payback should a Perth factory expect?
Here is a worked example with example figures. They are not our prices and not a real site.
A 100kW system in Perth is assumed to make about 1,600 kWh per kW a year, so 160,000 kWh in total. Each kWh the factory uses itself saves $0.28. Each kWh sent to the grid earns $0.00. The example price is $73,000 after the STC discount, the figure used on commercial solar cost.
| Shift pattern | Solar used on site | Saved on purchases | Earned on exports | Yearly saving | Years to pay back |
|---|---|---|---|---|---|
| One weekday day shift, closed weekends | 70% | $31,360 | $0 | $31,360 | 2.3 |
| Two shifts, six days a week | 85% | $38,080 | $0 | $38,080 | 1.9 |
The sums: 160,000 kWh × 70% = 112,000 kWh used on site × $0.28 = $31,360, plus 48,000 kWh exported × $0.00 = $0. Total $31,360 a year, and $73,000 ÷ $31,360 = 2.3 years. The second row works the same way at 85%.
Exports are set to zero because a commercial system in Perth is not covered by the buyback scheme and most contracts pay little or nothing. Even so, Perth's one-shift payback is the shortest in this series, and a factory that uses 85% of its output is under two years.
These sums leave out demand charges, the slow wear of panels and future price changes. The same table by site type is on commercial solar cost, and the full shift-pattern table is on solar for manufacturing.
What to send for a Perth manufacturing proposal
Just one recent electricity bill, with every page. The pages after the amount owing carry your tariff, your demand charge and your meter number. We use the meter number to get your interval data ourselves, so there is nothing to request from your retailer. For Perth we size to the plant's own daytime draw, because the surplus earns nothing, and we check which side of Western Power's 30 kVA line the system falls on so the proposal shows the right process and timeline.
If you already have a quote, compare it line by line with our checklist. Otherwise, send your bill.
Questions from Perth manufacturers
Will my factory be paid for solar it exports in Perth? Almost certainly not. The state's Distributed Energy Buyback Scheme covers residential, not-for-profit and educational customers with systems of 5kW or less, so a commercial system is outside it. What a retailer pays a business for exports is a contract matter and is usually small or nothing. A Perth proposal should count exports at zero; if it does not, ask why.
Why does the connection take longer above 30 kVA in Perth? Because above 30 kVA of inverter capacity a system leaves Western Power's basic embedded generator process and goes through a non-standard connection, with a technical assessment of the feeder and fees to match. Most factory systems are above the line. The proposal should say who lodges the application, what it costs and how long Western Power is currently taking, and the project plan should allow for it.
Does a Perth factory pay back faster than one in the eastern states? On the same shift pattern, yes. Perth's roughly 1,600 kWh per kW a year is the highest of the capitals, so the same 100kW system makes more and saves more, even with exports counted at zero. In our example a one-shift factory pays back in about 2.3 years and a two-shift factory in about 1.9. The shift pattern still matters more than the city: a Perth site that runs mainly at night does worse than a Brisbane one that runs all day.
Can a Kwinana or Welshpool site go above 100kW now? Yes. From 1 October 2026 a system between 100kW and 1MW can create STCs instead of large-scale certificates, with applications open from mid to late November 2026. In Perth the question is not the certificates but the load: with exports worth nothing, a system larger than the plant's daytime draw is paying for panels that earn nothing. The feeder assessment from Western Power is the other limit, and both belong in the proposal before a size is chosen.