About this tool
Wind Turbine Power Calculator is a free, in-browser tool that estimates the power a wind turbine produces from its rotor diameter, the wind speed and its efficiency. It returns the swept area, the peak power at that wind speed, the average power over time and the annual energy in kWh.
The power is P = 0.5 × ρ × A × Cp × v³, where ρ is air density (1.225 kg/m³ at sea level), A = π(d/2)² is the swept area, Cp is the power coefficient (real turbines reach 0.3–0.45; the Betz limit caps any turbine at 0.593) and v is wind speed in m/s. Because power scales with the cube of wind speed, doubling the wind gives eight times the power. Average power is peak × capacity factor, and annual energy is average power × 8760 hours ÷ 1000.
Use it to compare rotor sizes and sites for a small wind project: enter the blade diameter, your average wind speed, a realistic Cp and a capacity factor (15–30% is typical for small turbines) to see peak output and yearly kWh. All math runs in your browser.
Frequently asked questions
Why does wind speed matter so much?
Power grows with the cube of wind speed, so a site with 20% more wind yields about 73% more power. Accurate average wind speed is the single most important input — a modest turbine in strong wind beats a large one in weak wind.
What is the power coefficient Cp and the Betz limit?
Cp is the fraction of the wind's kinetic energy the rotor actually captures. Physics caps it at the Betz limit of 0.593; good real turbines reach 0.35–0.45 once blade, gearbox and generator losses are counted.
What is a capacity factor?
The wind is not always blowing at the speed you enter, so a turbine never runs at peak all year. Capacity factor is the ratio of actual annual output to running at peak the whole time — roughly 15–30% for small turbines, higher for large offshore ones.
Is the peak power what I get continuously?
No. Peak power is the instantaneous output at the exact wind speed you entered. Real average output is lower because wind varies — that is what the average-power and annual-energy tiles, driven by the capacity factor, estimate. Everything is computed locally.
More tools