Solar System Size Calculator

What this tool does

Estimate photovoltaic capacity and panel count from daily energy demand. Peak sun hours are not daylight duration. Shading, seasonal production, storage and export rules require site-specific design.

How to use the Solar System Size Calculator

1. Enter or select daily energy demand (kwh).
2. Enter or select peak sun hours per day.
3. Enter or select system output factor (%).
4. Enter or select panel rating (watts).
5. Read the calculated result; change any measurement to compare alternatives.

Formula

system kW=daily kWh/(sun hours×output factor/100); panels=ceil(system kW×1000/panel watts)

daily

Daily energy demand (kWh)

sun

Peak sun hours per day

efficiency

System output factor (%)

panel

Panel rating (watts)

Peak sun hours are not daylight duration. Shading, seasonal production, storage and export rules require site-specific design.

Worked example

For solar system size calculator, the following measurements illustrate the exact method: Daily energy demand (kWh): 30; Peak sun hours per day: 5; System output factor (%): 80; Panel rating (watts): 400.

Results explained

Required system (kW)

Required system (kW) from the formula above. Peak sun hours are not daylight duration. Shading, seasonal production, storage and export rules require site-specific design.

System capacity (kW)

System capacity (kW) from the formula above. Peak sun hours are not daylight duration. Shading, seasonal production, storage and export rules require site-specific design.

Panels

Panels from the formula above. Peak sun hours are not daylight duration. Shading, seasonal production, storage and export rules require site-specific design.

Frequently asked questions