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Solar PV Sizing Calculator

Determine your the size of your PV array

Solar Panel Array Sizing Calculator

Solar PV Array Calculator

System Size

0 W

Panels Needed

0

Designing a solar PV system

Photo by Chelsea on Unsplash

After understanding your energy requirements, and your battery requirements if you are off-grid, the next step is sizing your PV array so that you have enough power available even in the winter days.

Accurate solar array sizing is crucial for:

Avoid overspending on unnecessary panels

Maximize energy production year-round

Right-size your carbon footprint reduction

Prevent system overloads or shortages

How to Use Solar Calculator

How to Use this Calculator

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1. Daily Energy Requirement (kWh)

This is your total daily electricity consumption.

  • Find this on your electricity bill
  • Typical homes use 20-30 kWh/day
  • Include all appliances: lights, fridge, AC, etc.
Example: If your monthly usage is 900 kWh, daily = 900 ÷ 30 = 30 kWh

2. Daily Sunlight Hours

Use winter peak sunlight hours (PSH) for worst-case scenario planning:

  • Calculate using the lowest seasonal values
  • Winter typically has 60-70% of summer sunlight hours
  • Check data for your location from the NREL Solar Maps
  • Solar Radiation in kWh/m2/day is equal to the PSH. Use the lowest of all the months
  • Conservative estimates for US regions:
    • Southwest: 4-5 winter hours
    • Northeast: 2-3 winter hours
    • Midwest: 3-4 winter hours
Safety Margin: If your area gets 4 winter hours, use 3.5 in calculations

3. System Efficiency (%)

Accounts for energy losses in the system:

  • Typical range: 75-85%
  • Factors included:
    • Inverter efficiency (≈95%)
    • Temperature losses
    • Wiring losses
    • Dust/soiling
Default: Start with 80% if unsure

4. Panel Wattage (W)

Power rating of individual solar panels:

  • Common residential panels: 300-400W
  • Commercial panels: 400-600W
  • Check manufacturer specifications
Example: 400W panel produces 400 watts in ideal conditions

Understanding Results

System Size: Total wattage needed for your solar PV array. If you have an off-grid system, this is the watts needed to fully recharge your batteries on an avarage day in winter

Panels Needed: Number of panels required (rounded up) to provided the watts needed

Sample Calculation:
30 kWh ÷ (5 sun hours × 80% efficiency) = 7.5 kW → 7500W system
7500W ÷ 400W panels = 18.75 → 19 panels needed

💡 Pro Tips

  • Add 10-20% buffer for future energy needs
  • Consider seasonal variations in sunlight
  • Account for panel degradation (0.5-1% per year)
  • Consult a professional for exact system design
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⚠️ Disclaimer

The results provided by this calculator are for informational purposes only and should not be considered professional engineering advice. While we strive for accuracy:

  • This tool does not replace analysis by a qualified engineer
  • Results may vary based on real-world conditions and input assumptions
  • Final design decisions remain the responsibility of qualified personnel
  • We disclaim all liability for damages arising from use of these calculations

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