The Assumptions
Every input behind the figure. Interval data replaces each one.
Average retail rate$0.30 per kWh
Feed‑in rate5 c per kWh
Daytime shareby business type, 30% to 70%
Production yieldtypical for the state
Roof density0.15 kW per m²
For Australian businesses · free, no signup
Solar system size calculator: the kW that fits your site
Enter your electricity spend, state and business type. You'll see the system size, the incentive value and the annual saving straight away, with the maths shown.
- Warehouse, office, retail, more
- Sized to daytime use
- Roof area as the ceiling
Your Site
Defaults are an office in New South Wales spending $5,000 a month. Change anything and the figures update.
Sets the daytime share of use.
Covers NSW, VIC, QLD, SA and WA.
The monthly total from a recent bill.
Leave empty if the roof is not a limit.
Offices use steady 9-5 power, so solar self-consumption is high.
How this size is built
- Annual use
- 200,000 kWh
- Daytime share of use
- 70%
- Recommended system size
- 110 kW
- Annual production
- 142,211 kWh
- Upfront incentives
- $29,344
- Annual savings
- $42,111/yr
- Roof area
- not entered
The maths
How To Size Commercial Solar
Panels should match the power you use in daylight, not your total bill. The calculator turns your spend into annual use, takes the daytime share for your business type and sizes the system to cover it. Roof area is only a ceiling.
Daytime Share By Business Type
The share of use the system is sized to cover.
Office70%
Warehouse, retail60%
Manufacturing55%
Cold storage30%
Other50%
How To Size A Commercial System
Match the panels to the power you use in daylight. Oversize and you export surplus for a small feed-in credit. Undersize and you keep buying grid power at midday.
What The Calculator Weighs
Your annual use, the daytime share for your business type and your roof. A rule of thumb is 1 kW of panels for every 1,300 to 1,600 kWh you use in a year, but when your load runs matters more.
Why Bigger Is Not Always Better
Past your daytime demand, extra panels mostly feed the grid at a rate well below what you pay. Sizing to self-consumption keeps payback short.
Questions
Frequently Asked Questions
What size solar system does a warehouse need?
Warehouses commonly need 30 kW to 100 kW or more, depending on floor area, equipment and daytime hours. Sites with refrigeration or heavy machinery sit at the higher end.
How do I size a solar system for my business?
Match output to your daytime use. A common rule of thumb is to size to your daytime baseload, so most generation is used on site rather than exported at a low feed-in rate.
Can a commercial solar system be too big?
Yes. Past your daytime use, extra output is exported at a low feed-in rate, which lengthens payback. The right size balances self-consumption against upfront cost.
How does business type affect solar system size?
It decides when you use energy. A retail store uses most power in trading hours that line up with solar. A cold-storage warehouse runs 24/7 and uses less of what it makes. The calculator adjusts the size by consumption profile.
Related
Related Calculators And Guides
STC Calculator for AustraliaSTCs and their upfront value by postcode.VEEC Calculator for VictoriaVEECs for commercial solar in Victoria.LGC Calculator for AustraliaLGC revenue above the STC line.NSW Battery Rebate Calculator (PDRS)PRCs and the upfront discount for NSW batteries.Cheaper Home Batteries CalculatorBattery STCs under the federal program.Commercial Solar CalculatorSize, incentives and savings from your spend.Solar Payback CalculatorYears to pay back, by state.
Guides
Quoting commercial solar?
Model the whole site.
For solar professionals: bill in, every solar and battery size on one grid, five incentive schemes priced, a branded proposal out. About 10 minutes to a credible estimate.