Wind Turbine Size Selector

Calculate the optimal kW rating from wind speed and rotor swept area

Input Parameters

1 m/s 10 m/s 30 m/s
1 m² 100 m² 20,000 m²
11.28 m

Power Output Estimate

Estimated Power Output

68.75 kW

at rated wind speed

Available Wind Power

192.8 kW

Capture Efficiency

40%

Daily Energy (est.)

543 kWh

Annual Energy (est.)

198,188 kWh

📐 Recommended Turbine Class

Medium-scale (50–100 kW)

Suitable for small commercial or community wind projects

How the Calculation Works

P = 0.5 × ρ × A × v³ × Cp
P = Power output (Watts)
ρ = Air density (1.225 kg/m³ at sea level)
A = Rotor swept area (m²)
v = Wind speed (m/s)
Cp = Power coefficient (efficiency factor)
v³ = Wind speed cubed (cubic relationship)

* Daily and annual energy estimates assume a 35% capacity factor, which accounts for variable wind conditions.

Frequently Asked Questions

How is wind turbine kW rating calculated from wind speed and area?

Wind turbine power output is calculated using the formula P = 0.5 × ρ × A × v³ × Cp, where ρ is air density (1.225 kg/m³), A is the swept rotor area in square meters, v is wind speed in m/s, and Cp is the power coefficient (typically 0.35–0.45 for modern turbines). The cubic relationship with wind speed means doubling wind speed results in eight times more power.

What size wind turbine do I need for my location?

Turbine size depends on average wind speed at your site and the rotor swept area. Small residential turbines (1–10 kW) typically have rotor diameters of 1–7 meters and require average wind speeds above 4.5 m/s. Use this calculator to match your expected wind conditions and energy needs to the appropriate rotor area and rated power output.

What is the Betz limit and how does it affect turbine efficiency?

The Betz limit states that no wind turbine can capture more than 59.3% of the kinetic energy in wind (Cp max = 0.593). In practice, modern horizontal-axis wind turbines achieve a power coefficient of 0.35 to 0.45, meaning they convert 35–45% of available wind energy into electricity. This efficiency factor is already included in the calculator estimates above.