Wind Turbine Output

Free Wind Turbine Output calculator with clear step-by-step results.

About Wind Turbine Output

Wind power scales with the cube of speed and the square of rotor diameter, which is why site selection dominates turbine choice. The power coefficient cannot exceed the Betz limit of 0.593, and the capacity factor converts an instantaneous rating into realistic annual production.

Formulas

Power in the wind

P = 0.5 x air density x swept area x wind speed^3

Electrical output

P electrical = P wind x power coefficient x drivetrain efficiency

Worked example

With the default values below, Wind Turbine Output returns Annual energy production of 858.6. Change any input above and every figure here is recalculated in your browser.

Inputs used

Rotor diameterminimum 0.2 m: 3.5 m
Mean wind speed at hub heightaccepts 0.5–25 m/s: 6 m/s
Power coefficientaccepts 0.05–0.59: 0.35
Air densityaccepts 0.6–1.5 kg/m3: 1.225 kg/m3
Generator and inverter efficiencyaccepts 30–100 %: 88 %
Capacity factoraccepts 1–60 %: 25 %

Results

Annual energy production: 858.6 kWh
Electrical power at this wind speed: 392.0 W
Rotor swept area: 9.621 m2
Power in the wind: 1,272.9 W

Step by step

1Values used
2Power in the wind
3Electrical output
4Annual energy production= 858.6 kWh
5Electrical power at this wind speed= 392.0 W
6Rotor swept area= 9.621 m2
7Power in the wind= 1,272.9 W

Assumptions and limits

The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Small wind installations require planning permission and grid connection approval in most jurisdictions, and output on turbulent low-level sites is frequently far below manufacturer claims. Obtain a site wind assessment before investing.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Small wind installations require planning permission and grid connection approval in most jurisdictions, and output on turbulent low-level sites is frequently far below manufacturer claims. Obtain a site wind assessment before investing.

Frequently Asked Questions

Why can't a turbine extract all the wind energy?

Because the air has to keep moving to leave the rotor. Betz's law caps extraction at 59.3% of the kinetic energy, and real rotors reach 35-45%.

Is a 25% capacity factor realistic?

For a small turbine on an average inland site, yes - often lower. Good onshore wind farms reach 30-40% and modern offshore installations exceed 50%.