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Solar Panel Sizing Calculator

Reviewed by Engineering Team · Client-Side Execution

Determine the total photovoltaic (PV) array wattage and quantity of solar panels required based on your daily energy consumption and local peak sun hours.

⚡ Instant Browser Calculation 📐 Transparent Formula 🔒 100% Private (No data sent to server) 🆓 Free & Open Utility
Sum total of daily electricity used by appliances (1 unit on prepaid meter = 1 kWh).
Typical values: Southern Nigeria ~4.2 to 4.8 hrs; Northern Nigeria ~5.5 to 6.5 hrs.
Accounts for dust, temperature derating, inverter loss, and wire resistance (typically 20% - 30%).
Calculated Output
1,733 Watts (Wp) Equivalent to approx 4 x 450W panels or 6 x 300W panels.
FASTRuns instantly in your browser
CLEARTransparent step-by-step logic
PRIVATENo server data collection

Mathematical Sizing Formula

This estimator calculates the required DC nameplate wattage of your solar photovoltaic (PV) array by adjusting for real-world environmental and electrical losses:

Required Array Watts (Wp) = [Daily Energy Demand (kWh) / (1 - Inefficiency Loss)] × 1,000 / Peak Sun Hours

Where Inefficiency Loss represents system derating (such as 0.25 for 25% loss), scaling up total raw kilowatt-hour generation before dividing across usable solar hours.

Practical Worked Example

Consider a 3-bedroom residence in Lagos or Abuja with a daily load profile of 6.5 kWh (running a refrigerator, TV, lighting, fans, and laptop work stations):

  • Gross Generation Needed: 6.5 kWh ÷ (1 - 0.25) = 8.67 kWh
  • Wattage Required: (8.67 × 1,000) ÷ 5.0 sun hours = 1,733 Watts peak (Wp)
  • Panel Count Recommendation: Sizing with modern 450W mono-perc panels requires 1,733 / 450 = 3.85 → rounded up to 4 panels (1,800W total array).

Important Limitations & Nigerian Context

Peak sun hours fluctuate across seasons. During the height of the West African monsoon (June to August), solar insolation can drop by 20–35%, requiring adequate inverter battery storage or generator backup to bridge extended overcast days.