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Power capture depends on the area swept by the rotor blades. Larger diameter captures exponentially more energy because swept area grows with the square of radius.
A = π × (D/2)² (m²)Available wind power is proportional to air density, swept area, and wind speed cubed. Small increases in wind speed produce large output gains.
P = 0.5 × ρ × A × v³ (Watts)No turbine captures more than 59.3% of available wind energy (Betz limit). Real turbines achieve 35–45% of available power after blade, gearbox, and generator losses.
Electrical output = P × Cp × η_generator (Cp ≤ 0.593)Updated: July 2026
A 3.5m diameter turbine at 6 m/s (13.4 mph) average wind with Cp=0.35 produces roughly 800–1,200W. Needs consistent 5+ m/s site to approach rated 3 kW at 11 m/s.
10m rotor at 7 m/s with 40% efficiency yields ~15–20 kW. At 5 m/s the same turbine produces only ~4 kW — wind speed cubed makes site selection critical.
A 2m turbine supplements solar in windy winter months. At 8 m/s produces ~400W — meaningful overnight and cloudy-day contribution when solar output drops.
Turbines reach rated power only at high wind speeds (11–13 m/s). Average site wind of 5–6 m/s typically produces 15–25% of rated capacity. Check power curve at your actual wind speed.
Buildings and trees create turbulent air that reduces output 20–40% below free-stream calculations. Turbines need hub height 30 feet above obstacles within 500 feet.
Wind turbine power depends on rotor swept area, wind speed cubed, air density, and turbine efficiency. This calculator estimates electrical output in watts from rotor diameter, hub height wind speed, and generator efficiency using the standard wind power equation.