Solar Panel Calculator
Estimate number of solar panels needed based on monthly electricity usage, location, and panel wattage.
About the Solar Panel Calculator
Estimate number of solar panels needed based on monthly electricity usage, location, and panel wattage.
Solar Panel Calculator estimates how many panels your home needs based on monthly electricity consumption, local sun hours, and panel wattage. It factors in the 80% real-world efficiency that most solar calculators ignore — so you get a number that actually works, not a best-case fantasy.
- Type
- Calculator
- Runs in
- Your browser — no account, no install
- Price
- Free
- Results
- Instant, with plain-English interpretation
Solar Panel Calculator
Frequently asked questions
A typical Indian home using 300 kWh/month needs 6-8 panels (3 kW system). A US home using 900 kWh/month needs 18-22 panels (8-9 kW system). This varies significantly by location, panel efficiency, and roof orientation.
Peak sun hours = hours when sunlight intensity equals 1000 W/m². Not just daylight hours. India averages 4-6 hours. US Southwest: 5-6, Northeast: 3-4. Search 'peak sun hours [your city]' for local data. This directly affects how many panels you need.
Real systems lose 15-25% to inverter conversion, wiring, dust, temperature, and shade. Most marketing uses 100% efficiency. Our 80% factor gives you a realistic number that matches actual production after installation.
A standard 400W panel is about 21 sq ft (2m × 1m). For 20 panels, you need roughly 420 sq ft of unshaded, south-facing roof. Factor in spacing between rows and edge setbacks required by local building codes.
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