Is solar actually worth it for your business? It’s the first thing most owners ask, and a commercial solar ROI calculator is the quickest way to get a feel for the answer. Type in your power use, how much of it happens in the daytime, your system size, and what it costs to install. Out comes a rough picture of your yearly savings, how long the system takes to pay itself off, and the return you could expect. It gives you a useful starting point before requesting a commercial solar assessment.
Under the calculator, we walk through the maths one step at a time, so nothing feels like a black box. After that, you’ll find two worked examples (a 100 kW warehouse and a 30 kW workshop) and a plain-English rundown of the Australian incentives on offer, including mid-scale STCs from 1 October 2026.
One honest heads-up first. Everything here is an estimate. Your real numbers depend on your interval data, your tariffs, how the system performs, and what the install costs are, and only a site-specific assessment can provide a reliable project estimate.
Commercial Solar ROI Calculator
It takes your electricity use, system size, and install cost and turns them into estimated yearly savings, simple payback, and first-year commercial solar ROI. Think of the result as a starting point, not a promise. Demand savings, tax benefits, maintenance, and financing are left out unless you add them yourself.
Here’s what it asks for, with example values:
| Input | Example |
| Annual electricity consumption | 150,000 kWh |
| Daytime electricity usage | 75% |
| Electricity usage rate | $0.24/kWh |
| Solar export rate | $0.05/kWh |
| Solar system size | 100 kW |
| Peak sun hours (from postcode) | 4.0 |
| Performance ratio | 0.8 |
| Installed system cost | $120,000 |
| STC zone rating and deeming period | Zone 3, 5 years |
| Estimated self-consumption | 85% |
| Verified demand charge savings (optional) | $2,000 |
Daytime electricity consumption and solar self-consumption are separate inputs. The former describes your business’s electricity demand, while the latter measures how much of the generated solar electricity is used directly.
How to use it
- Grab your last 12 months of bills and put in your consumption and tariff rates.
- Add your system size, install cost, and postcode so the right STC zone and sun hours kick in.
- Pop in a self-consumption rate. If you have interval data, use your solar model’s number. If not, go conservative and treat it as a guess.
- Only add demand savings if your interval data backs them up.
- Change a few inputs and run it again. Playing with scenarios is the best way to see what really moves the numbers.
What the results mean
Annual savings is how much less you’ll pay on bills in year one. It isn’t profit. Simple payback is how many years of savings it takes to cover your net cost, and first-year ROI is year-one savings as a percentage of that cost. If your CFO or lender asks about IRR and NPV, those look at the return across the system’s whole life.
Getting your interval data
Interval data is your usage in 30-minute blocks. Line it up with modelled half-hourly solar output and you can see how much solar you’d really use, which beats annual totals by a mile. Ask your retailer or distributor, and have your National Metering Identifier (NMI) ready. Your installer can request it too, with your consent. Timing varies by network. Ausgrid, for example, wants the NMI, account holder surname, and postcode exactly as they appear on your bill, and says to allow 10 to 20 business days.
How to Work Out Your ROI in 5 Steps
Here’s the whole thing in five steps. Nothing fancy, just a bit of multiplication.
Step 1: Figure out how much power your system will make
Annual generation (kWh) = System size (kW) × Peak sun hours × 365 × Performance ratio
Peak sun hours come from the Bureau of Meteorology’s solar exposure maps (14.4 MJ/m² works out to 4 peak sun hours), and NREL’s PVWatts is a handy way to double-check. The performance ratio covers the losses you’ll always get from heat, wiring, dust, and inverters. Around 0.8 is typical, but treat it as a sensible guess rather than a promise. For our 100 kW example, that’s 100 × 4 × 365 × 0.8, or 116,800 kWh a year.
Step 2: Work out how much you’ll actually use
Self-consumption is simply how much of your solar your business uses directly. It’s the number that moves your payback the most, and interval data is the best way to pin it down. If you don’t have that data yet, pick a cautious percentage and be upfront that it’s an assumption. Whatever you don’t use gets exported.
Step 3: Turn it into dollars
Annual savings = (Self-used kWh × Usage rate) + (Exported kWh × Export rate) + Verified demand savings
Only count demand savings if your interval data backs them up. Your peak might land at 7am or 5pm, well outside strong sun. And keep in mind that this is bill savings, not profit.
Step 4: Take off the incentives
Net cost = Gross installed cost – STC benefit
The STC benefit depends on whether you’re eligible, how many certificates you get, and how much your installer passes on. Keep tax deductions separate, since they depend on your own tax position.
Step 5: Get your payback and ROI
Simple payback (years) = Net cost ÷ Year-one savings
First-year ROI (%) = Year-one savings ÷ Net cost × 100
For the warehouse below, $93,742 ÷ $26,703 comes to about 3.5 years, with a first-year ROI of about 28.5%. This simple method leaves out tariff increases, degradation, maintenance, financing, and inverter replacement, so if you’re taking this to a board, use escalated or discounted payback instead.
Two Examples: A Warehouse and a Workshop
Returns swing a lot depending on how a business uses power. So here are two Australian businesses: commercial solar for warehouses and workshops. A warehouse with steady daytime demand, and a workshop with a shorter day and lumpier equipment loads.
| Metric | Warehouse | Workshop |
| System size | 100 kW | 30 kW |
| Operating pattern | Mon to Sat, daytime | Mon to Fri, 7 am to 4 pm |
| Annual generation | 116,800 kWh | 35,040 kWh |
| Self-consumption | 85% | 65% |
| STCs (Zone 3, 2026) | 691 | 207 |
| STC value at $38 | $26,258 | $7,866 |
| Gross installed cost | $120,000 | $42,000 |
| Net cost (after STCs) | $93,742 | $34,134 |
| Demand charge savings | $2,000 | $0 |
| Annual savings | $26,703 | $6,079 |
| Simple payback | 3.5 years | 5.6 years |
| First-year ROI | 28.5% | 17.8% |
Assumptions: Zone 3, 4.0 peak sun hours, 0.8 performance ratio, 24 c/kWh avoided usage, 5 c/kWh export, and STCs at $38 (as of November 2026, so check the current price). These are illustrative estimates, not customer results or guaranteed returns.
The warehouse runs lighting, cooling, and forklift charging all day, so it uses most of what it generates. That’s 99,280 kWh × $0.24 = $23,827 saved, plus 17,520 kWh exported at $0.05 for $876, plus a $2,000 demand saving. Total: $26,703 a year.
The workshop has a tougher time. Compressors and welders create short peaks solar can’t always cover; the day is shorter, and weekend generation exports at a low rate. It saves 22,776 kWh × $0.24 = $5,466, plus 12,264 kWh exported for $613, so $6,079 a year. If it could lift self-consumption to 85%, savings would rise to about $7,411, and payback would drop to about 4.6 years. That’s a what-if, not a promise.
Commercial payback often beats residential because businesses use power while the sun is up. For your own number, check current commercial solar installation costs and ask for a site-specific quote.
6 Factors That Affect Commercial Solar ROI
- Daytime usage. A kWh you use yourself saves the full usage rate. A kWh you export earns a few cents. So loads running between 7 am and 5 pm are worth far more than morning and evening ones.
- Your tariff. Time-of-use peak and shoulder rates make daytime solar more valuable, so check yours before trusting a flat-rate estimate.
- Demand charges. Solar only helps if your peak lands in strong sunlight. Look at your interval data first.
- Connection limits. Rules differ by network. Ausgrid still runs a capacity assessment above 30 kVA, Jemena negotiates from 30 kVA up to 1 MVA, and Evoenergy has relaxed rules up to 200 kVA for most systems. Check yours early.
- System size and cost. Bigger systems cost less per watt, but only pay off if you use the output. Switchboard upgrades, structural work, three-phase upgrades, and grid connection can add costs the headline price skips. If you use a lot of power in the evening, commercial solar battery storage is worth a look as a separate investment.
- Degradation and upkeep. Panels lose a little output each year, so check the output warranty, and budget for commercial solar maintenance and maybe a mid-life inverter replacement.
Incentives and Tax Benefits in 2026
Australian businesses may be eligible for financial incentives and tax deductions when installing commercial solar systems. The available benefits depend on system capacity, installation date, related generation capacity and the business’s tax eligibility.
| System capacity | Potential incentive | Worth knowing |
| Up to 100 kW | STCs | Deeming period depends on installation year. Usually passed on by your installer as an upfront discount |
| Above 100 kW to 1 MW | STCs or REGO | For installations from 1 October 2026. Applications to the Clean Energy Regulator are expected to open mid to late November 2026 |
| Over 1 MW | Potential LGCs | Needs large-scale scheme accreditation, so ask your installer |
STCs up to 100 kW
STCs = System capacity (kW) × Zone rating × Deeming period
The deeming period drops by a year every year until the scheme ends in 2030: 5 years in 2026, then 4, 3, 2, and 1 from 2027 to 2030. That’s why timing matters. A 100 kW Zone 3 system earns about 691 STCs this year but only about 552 in 2027, which is roughly $5,300 less at $38 each.
Mid-scale: above 100 kW to 1 MW
From 1 October 2026, these systems can claim STCs too, with a fixed five-year deeming period. A 200 kW Zone 3 system would earn about 1,382 STCs, or roughly $52,500 at $38 each. The 1 MW limit counts the combined capacity of related systems at your site, so check your eligibility with the Clean Energy Regulator, including its mid-scale STC calculator, before you count on a number.
Tax benefits
Small businesses with aggregated turnover under $10 million that use simplified depreciation can immediately write off eligible assets costing under $20,000 each. The ATO describes that threshold as permanent from 1 July 2026. Most commercial systems cost more, so they usually go into the small business pool, depreciated at 15% in the first year and 30% of the opening pool balance after that. Deductions reduce your tax, not the installation invoice, so have a chat with your accountant, including about GST.
Does Financing Change the Picture?
Financing doesn’t change what your system saves. It changes who pays, when, and who gets the incentives, so read the contract closely.
| Model | Upfront cost | Who claims incentives | Effect on payback |
| Outright purchase | Full net cost | You | Standard payback formula applies |
| Solar loan | Low or none | Usually you | Interest adds to total cost, so compare repayments with monthly savings |
| Lease | Low or none | Check the contract | Use net monthly cash flow instead |
| PPA | None | Check the contract | Savings are the gap between the PPA and grid rates |
For example, if a business saves an estimated $2,000 a month but pays $1,500 a month in loan repayments, that’s about $500 of positive monthly cash flow before maintenance and other expenses.
So, Is It Worth It?
Honestly? It depends on how your business uses power. If your place is humming while the sun’s up, with lights on, machines running, fridges working, and chargers plugged in, solar can be a brilliant fit. If your days are shorter or your usage is patchier, it can still stack up. It’ll just take a little longer to pay itself off, and that’s completely normal.
The best next step is simple. Dig out your last 12 months of bills and your interval data, run the calculator, and see what comes back. Then get two or three quotes from installers who’ve looked at your site, and ask each one which incentives apply to your system. A handful of real quotes will teach you more than any rule of thumb in this guide, ours included.
And if the first result isn’t what you were hoping for, don’t write solar off. Try a different system size, review your daytime usage, and run it again. A small tweak can change the picture more than you’d expect.
Want a hand with it? Austar Solar can look at how your business uses power and design a system around that.
FAQs on Commercial Solar ROI
Is commercial solar worth it in Australia?
Often, yes, particularly if most of your power gets used in daylight hours. Sites with strong daytime demand can see payback in the low-to-mid single-digit years, while weekday-only businesses with smaller loads usually wait a bit longer. The only way to know for sure is to check it against a real quote.
How accurate is a commercial solar ROI calculator?
It’s a solid first estimate, but it’s only as good as the numbers you feed it. Bring your real interval data and actual tariff, and it gets much more reliable. Guess the inputs, and you’ll get a ballpark. For true costs and returns, you’ll want a site assessment.
What’s a good ROI for commercial solar?
There’s no magic number, because it depends on how much solar you use yourself, your tariffs, and what the system costs. In our examples, the warehouse landed on a first-year ROI of 28.5% and the workshop 17.8%. A better test is to compare your own result against your financing costs and what else you could do with the money.
Can a battery improve my ROI?
Sometimes. A battery can shift extra solar into the evening and take the edge off demand peaks, but it adds a big upfront cost. It tends to suit businesses that use a lot of power in the evening or overnight. Treat it as its own investment and model it with your interval data.
