Investing in solar is one of the smartest moves a business can make—but choosing the right system size is critical. Too small, and you won’t offset enough of your electricity use. Too large, and you risk unnecessary upfront costs or wasted generation.

So, how do you figure out the right size solar system for your business?

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1. Understand Your Energy Usage

The first step is to look at your electricity bills. You want to understand:

• How much power you use (kWh) on a monthly and yearly basis

• When you use the most power—during the day, at night, or seasonally?

Look for your average daily usage, which is usually displayed on your bill in kilowatt-hours (kWh). This tells you how much energy you need to offset.

Example: If your business uses 120 kWh/day, you’ll want a solar system that can generate around that amount during daylight hours.

2. Match System Size to Your Usage

Here’s a rough guide for system sizes based on daily electricity use:

Rule of thumb: In full sun, each 1kW of solar panels produces about 4 kWh/day. So a 25kW system would generate roughly 100 kWh/day in good conditions.

3. Consider Your Roof Space

Commercial buildings usually have decent roof space, but panel placement and orientation matter.

• North-facing roofs (in Australia) get the best sunlight

• You’ll need approx. 6–7m² per kW of solar

• Shading from HVAC units, trees, or other buildings can reduce performance

If roof space is tight, you might opt for higher-efficiency panels or consider a ground-mounted or solar carport option.

4. Think About Your Business Hours

Solar systems produce electricity during daylight. So if your operations run mostly during the day (e.g. retail, offices, warehouses), you can directly consume the power generated, improving your ROI.

If your business operates at night (e.g. hospitality, cold storage), pairing solar with battery storage or choosing a smaller system with feed-in credits might be smarter.

5. Plan for Growth

Is your energy usage likely to increase in the next 5–10 years? For example, are you:

• Adding new machinery or equipment?

• Expanding your facilities?

• Planning electric vehicle (EV) charging stations?

If so, it may be worth sizing up now to “future-proof” your energy supply—especially while solar rebates are still available.

6. Factor in Your Budget and Payback Goals

Larger systems cost more upfront, but they can deliver better long-term savings. Still, every business has different financial goals.

• Want a faster payback period? Size your system to match your daytime usage closely.

• Want maximum offset? Consider a larger system with potential export back to the grid.

Your installer should model different system sizes against your bills to show the projected savings and payback timeline.

7. Get a Custom Assessment

Online calculators are helpful for ballparks, but a proper site inspection and usage analysis is the best way to determine your ideal system size. A professional commercial solar provider will:

• Review your electricity usage data

• Inspect your roof and electrical systems

• Model your ROI with accurate solar production estimates

• Advise on rebates, tax incentives, and financing options

Conclusion: Right-Size It for Long-Term Wins

There’s no one-size-fits-all answer—your ideal solar system depends on your energy habits, roof space, budget, and future plans.

Working with an experienced commercial solar installer ensures you don’t overpay or under-power your system. A well-sized solution means more savings, quicker returns, and less risk.