Cost, payback and rebates
What commercial solar costs, and when it pays for itself
Real dollar ranges by system size, the STC discount explained without the sales spin, and payback maths shown rather than asserted.
The short answer
Commercial solar in Australia costs roughly $700 to $1,100 per kilowatt installed before rebates, falling to about $620 to $840 per kilowatt after the federal STC discount on systems up to 100kW. Payback lands between 2.5 and 4 years for a business that uses most of its power in daylight hours, and stretches beyond that for one that doesn't. Only Victoria has offered a state-level commercial rebate in recent years. Everywhere else, STCs are the whole of the upfront support.
Cost by system size
| System | Roof area | Installed | After STCs | Saved a year | Payback |
|---|---|---|---|---|---|
| 30 kW~54 panels | 150–190 m² | $28,000 – $38,000 | $21,000 – $29,000 | $7,000 – $11,000 | 2.8 – 4.1 years |
| 50 kW~90 panels | 250–320 m² | $44,000 – $58,000 | $33,000 – $44,000 | $12,000 – $18,000 | 2.6 – 3.8 years |
| 100 kW~180 panels | 500–620 m² | $82,000 – $110,000 | $62,000 – $84,000 | $24,000 – $36,000 | 2.5 – 3.6 years |
Ranges, not quotes. Roof type, switchboard condition, network approval and how much of your load falls in daylight hours move every one of these numbers. The proposal you get back replaces this table with figures for your site.
How the STC discount actually works
Small-scale Technology Certificates are the federal government's support for solar systems up to 100kW, and they're the reason a commercial quote shows two prices. The certificates are created upfront based on three things: how big the system is, which of the four zone ratings your postcode falls into, and how many years are left in the scheme, which winds down to nothing in 2030.
You almost never touch this. The installer claims the certificates and takes their value straight off your invoice, so what you see is a discounted price rather than a rebate you apply for and wait on. The value shifts with the market price of certificates, which is why a quote from March and a quote from November can differ on the same system.
Two things worth knowing. The zone rating matters, and it's why the same 50kW system attracts a bigger discount in Brisbane or Perth than in Melbourne. And the 100kW ceiling is a real cliff: cross it and you move to Large-scale Generation Certificates, which pay out over the life of the system rather than upfront and involve far more administration. A 99kW system and a 110kW system are different financial products.
The scheme's rules and current zone map are published by the Clean Energy Regulator.
Payback, with the working shown
Take a 50kW system on a Brisbane warehouse. Here's the arithmetic anyone quoting you should be willing to write down.
| System size | 50 kW | Sized to the site's daytime load, not the roof area |
|---|---|---|
| Annual generation | 72,500 kWh | At roughly 1,450 kWh per kW a year in Brisbane |
| Self-consumed | 80% | 58,000 kWh used on site rather than exported |
| Grid rate avoided | $0.28 / kWh | What the business would otherwise pay |
| Saving on consumption | $16,240 | 58,000 kWh × $0.28 |
| Export earnings | $725 | 14,500 kWh exported at roughly $0.05 |
| Total annual benefit | $16,965 | Before any demand-charge reduction |
| Cost after STCs | $38,000 | Mid-point of the 50kW range |
| Payback | 2.2 years | $38,000 ÷ $16,965 |
Change one assumption and the answer moves a long way. Drop self-consumption from 80% to 40%, which is what happens on a site that runs evenings, and the annual benefit falls to around $8,850 with payback stretching past four years. That single number, how much of your generation you use rather than sell, does more to decide whether commercial solar works for you than the price of the panels.
It's also the number a quote built without your bill has to guess at. Which is the whole argument for starting with the bill.
State by state, what exists and what doesn't
Western Australia
No commercial rebate. Exports paid under the Distributed Energy Buyback Scheme, which pays little at midday and more in the evening peak. Systems here earn their keep by covering daytime load.
Detail for this stateQueensland
No standing commercial rebate. STCs are worth more here than in the southern states because of the zone rating. Feed-in rates in the south-east are set by retailers, not government.
Detail for this stateVictoria
The only state on this site to have run a business solar program in recent years, through Solar Victoria. Whether one is open when you apply changes, so it gets checked against your eligibility rather than promised upfront.
Detail for this stateSouth Australia
No commercial rebate, and the highest rooftop solar penetration in the country. Midday exports are worth very little, so the value sits almost entirely in self-consumption.
Detail for this stateState programs open and close. Confirm the current position on the relevant state government site before you budget around any of them.
Cost and rebate questions
What does commercial solar cost in Australia?
For a 30kW system, roughly $28,000 to $38,000 installed before the STC discount, and about $21,000 to $29,000 after it. A 100kW system runs to roughly $82,000 to $110,000 installed, or $62,000 to $84,000 after STCs. Roof type, switchboard capacity and network approval conditions move those figures.
How does the STC discount work for commercial solar?
Small-scale Technology Certificates apply to systems up to 100kW. They're created upfront based on the system size, your location's zone rating and the years left in the scheme, and the installer almost always claims them for you and takes the value off the invoice. You don't apply for anything and you don't wait for a payment. Systems above 100kW use Large-scale Generation Certificates instead, which pay out over time rather than upfront.
What is a typical payback period for commercial solar?
Two and a half to four years for a business that uses most of its power during daylight hours. It stretches out for a site that draws mainly at night, because the value sits in offsetting power you'd otherwise buy rather than in exporting. A warehouse running day shifts and a pub trading evenings get very different answers from the same roof.
Are there state rebates for commercial solar?
Mostly no. Victoria has run business solar programs through Solar Victoria. Western Australia, Queensland and South Australia have no standing commercial rebate, so the federal STC discount is the whole of the upfront support in those states. Check the current position on the relevant state government site before budgeting for anything else.
Does commercial solar still pay off if we can't export?
Often yes. Export earnings are a small part of the return on most commercial systems, because feed-in rates are low and midday wholesale prices in some states sit near zero. If your business consumes most of what it generates, a zero-export system can still pay back in a similar window. Ask for the numbers with export revenue set to zero and see whether they hold.
Can we claim commercial solar as a tax deduction?
A solar system is a depreciating asset for a business, so it's generally depreciated rather than deducted outright, and the applicable rules change with whatever instant asset write-off threshold is current. This one needs your accountant rather than a solar company, and anyone quoting you a tax outcome as part of a sales pitch is out of their lane.
Get these numbers for your site
One recent bill is enough to size a system and price it. It costs nothing, there's no obligation, and you'll hear back within 48 hours.