Solar Panel Output Calculator
Calculate daily and monthly energy output from your solar panels.
Factor in panel wattage, sunlight hours, and system efficiency.
Daily Energy Output
Solar panel output depends on three main factors: panel wattage (rated power), peak sun hours at your location, and system efficiency losses.
The formula: Daily output (kWh) = panel wattage (W) × number of panels × peak sun hours × efficiency factor / 1000
Peak sun hours by region (approximate):
- Northern Europe (UK, Germany, Scandinavia): 2.5–3.5 hrs/day
- Central Europe (France, Austria): 3.5–4.5 hrs/day
- Southern Europe (Spain, Italy, Greece): 4.5–6.0 hrs/day
- Middle East / North Africa: 5.5–7.0 hrs/day
- US Northeast: 3.5–4.5 hrs/day
- US Southwest: 5.5–7.0 hrs/day
- Australia (most areas): 4.5–6.0 hrs/day
Efficiency losses (typical):
- Temperature derating: −5% (panels lose efficiency in heat)
- Inverter losses: −5%
- Wiring and connection losses: −3%
- Soiling / shading: −3%
- Total typical loss: ~15% → efficiency factor = 0.85
Worked example: 10 × 400W panels, 4.5 peak sun hours, 0.85 efficiency: Daily output = 10 × 400 × 4.5 × 0.85 / 1000 = 15.3 kWh/day
At an average EU household consumption of 3,000–4,000 kWh/year (8–11 kWh/day), this system would cover most or all of a typical home’s needs.