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Solar system size calculator

Estimate the right commercial solar system size for your business based on your electricity spend, business type, and available roof space.

Business type

State

Monthly electricity spend ($)

Available roof area (m²) — optional

Recommended system size

140–170 kW

Estimated upfront incentives

$41,771

Estimated annual savings

$60,117/yr

Based on $5,000/month electricity spend in NSW.

How this size is built

Estimated annual consumption: 200,000 kWh
Recommended system size: 155 kW
Annual production: 200,389 kWh
Estimated upfront incentives: $41,771
Estimated annual savings: $60,117/yr

Offices have consistent 9-5 consumption, so solar self-consumption is high.

New rule. This size sits above 100 kW, so the incentive value uses the SRES 1 MW expansion, which applies to systems installed from 1 October 2026: the whole system earns upfront STCs at a fixed 5-year deeming instead of LGCs, up to the first 1 MW; capacity above that still earns LGCs. What changes.

Estimate only. Assumes an average rate of $0.30/kWh, a typical production yield for your state, and 0.15 kW of panels per m² of roof. Interval data replaces every one of those assumptions.

Get a full solar estimate All solar incentives

How to size commercial solar

How to size a commercial system

The right size matches the panels to the power you actually use during daylight, not just your total bill. Oversize the system and you export cheap surplus for a small feed-in credit; undersize it and you keep buying expensive grid power through the middle of the day. The sweet spot is the system that covers most of your daytime load.

What the calculator weighs

It looks at your annual consumption, the shape of your working day, and how much unshaded roof or ground you have to work with. A rule of thumb is roughly 1 kW of panels for every 1,300 to 1,600 kWh you use in a year, but when your load runs matters more than that headline number.

Why bigger is not always better

Past the point where solar covers your daytime demand, extra panels mostly feed the grid at a feed-in tariff well below what you pay to buy power back. Sizing to self-consumption keeps the payback short and the return sound. Enter your usage above to see the kW range that fits your site.

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 loads, and daytime operating hours. Sites with refrigeration or heavy machinery sit at the higher end.

How do I size a solar system for my business?

Match system output to your daytime consumption. A common rule of thumb is to size to your daytime baseload so most generation is self-consumed rather than exported at low feed-in rates.

Can a commercial solar system be too big?

Yes. Oversizing beyond your daytime consumption exports excess energy at low feed-in rates, which lengthens payback. The right size balances self-consumption against upfront cost.

How does business type affect solar system size?

Business type determines when energy is consumed. A retail store uses most power during trading hours that align well with solar generation. A cold-storage warehouse runs 24/7 with lower self-consumption. The calculator adjusts the sizing estimate by consumption profile.