Solar Panel Calculator

Calculate how many solar panels you need based on your daily energy consumption. This calculator helps you determine the right size for your solar power system.

Your average daily electricity consumption
Average peak sun hours in your location (typically 4-6 hours)
Power rating of each solar panel (common sizes: 300W-500W)
Total system losses including inverter, wiring, dust, etc. (typically 20-25%)

Results

How to Use This Calculator

  1. Daily Energy Usage: Enter your average daily electricity consumption in kilowatt-hours (kWh). You can find this on your electricity bill or by dividing your monthly usage by 30.
  2. Peak Sun Hours: Enter the average number of peak sun hours in your location. This varies by geography and season.
  3. Panel Wattage: Enter the power rating of the solar panels you plan to use. Modern panels typically range from 300W to 500W.
  4. System Losses: Account for various system losses including inverter efficiency, wire losses, dust, and temperature effects.

Understanding the Results

  • Required System Size: The total solar power system capacity needed in kilowatts (kW).
  • Number of Panels: The estimated number of solar panels needed to meet your energy requirements.
  • Roof Area: Approximate roof space needed for the solar panel installation (assumes 2m² per panel).

Note: This calculator provides estimates based on typical conditions. Actual requirements may vary based on specific local factors such as:

  • Local climate and weather patterns
  • Roof orientation and tilt
  • Shading from nearby objects
  • Local installation regulations

For precise calculations, consult with a local solar installation professional.

What the numbers mean in practice

Peak sun hours is the figure that surprises people most. It is not daylight hours: it is the equivalent number of hours at full 1,000 W/m² irradiance. A location with fourteen hours of summer daylight may still only deliver five peak sun hours, and the same place drops to one or two in midwinter. Sizing an array on the annual average leaves a system that covers the bill in July and falls short in January.

System losses cover everything between the cell and the meter: inverter conversion, wiring resistance, soiling, mismatch between modules, and the temperature effect on the cells themselves. Twenty-three per cent sounds pessimistic until each part is listed separately, at which point it usually turns out to be about right.

The roof area figure assumes roughly two square metres per panel and no obstructions. Real roofs have vents, chimneys, edge setbacks required by fire regulations and areas shaded for part of the day, so the usable area is normally smaller than the raw measurement.

Where to go next

Once you know the array size, the follow-up questions each have their own tool. Panel angle and panel spacing settle the layout; battery bank size covers storage; wire size and circuit protection handle the electrical side; and payback period answers whether the whole thing is worth building.

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Main solar calculators

Battery calculators

Wiring and electronics

Energy and cost

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