Solar Panel Sizing Calculator ☀️
How to Use the Solar Panel Sizing Calculator
Enter daily consumption (Wh), peak sun hours for your location, and system efficiency. Formula: Required capacity (W) = daily consumption / (sun hours × efficiency).
Peak sun hours vary by location: tropical regions ~6h, temperate ~4.5h, northern regions ~3.5h. Use the regional presets as a starting point.
System efficiency accounts for inverter losses, wiring losses, and temperature effects. A default of 80% is typical for most systems. Size up if you have high loads or limited sun.
FAQ
How many solar panels do I need for a 3,000 Wh/day system?
With 5 peak sun hours and 80% efficiency: 3,000 / (5 × 0.8) = 750W required. That's 3 × 250W panels or 2 × 400W panels. Always round up for safety margin.
What are peak sun hours and how do I find mine?
Peak sun hours represent the equivalent hours of full 1,000 W/m² sunlight per day. Tropical regions average 5–6h, temperate zones 3.5–5h, northern regions 2.5–3.5h. Use NASA's PVGIS tool for your exact location.
Why is system efficiency less than 100%?
Losses come from inverter inefficiency (5–10%), wiring resistance (2–3%), battery charging losses (5–15%), and temperature derating (5–15% in hot climates). A realistic efficiency factor is 70–85%.
Should I oversize my solar array?
Yes, by 20–30%. Oversizing compensates for cloudy days, panel degradation (0.5%/year), and seasonal variation. A larger array also charges batteries faster on good days.
What is the difference between panel wattage and actual output?
Panel wattage (STC rating) is measured under ideal lab conditions. Real-world output is typically 75–85% of rated wattage due to heat, angle, and atmospheric conditions.