Solar Panel Estimator

Calculation Method

The solar panel estimator uses these steps to determine your system requirements:

1. Annual energy need = monthly usage × 12 × (offset target / 100)
2. Required daily production = annual need ÷ 365
3. Adjusted for efficiency = daily production ÷ system efficiency
4. System size (kW) = adjusted daily production ÷ peak sun hours
5. Number of panels = system size ÷ individual panel wattage
6. Roof area check = panels needed × panel size vs. available roof area

Peak Sun Hours by Region

• 3–3.5 hours: Northern US, UK, Scandinavia, Pacific Northwest
• 4–4.5 hours: Central US, Central Europe, Japan
• 5–5.5 hours: Southern US, Mediterranean, Eastern Australia
• 6–7 hours: Desert Southwest, Middle East, Tropical regions

Tips

• Peak sun hours are not the same as daylight hours — they represent equivalent hours of full-intensity sunlight
• South-facing roofs (in the Northern Hemisphere) receive the most sunlight
• Shading from trees or nearby buildings can reduce output significantly
• Panel output degrades roughly 0.5% per year over their 25–30 year lifespan
• Many regions offer tax credits or incentives that reduce the installed cost