🌬️ Wind Turbine Output

Written and maintained by the PhDino author · Last reviewed 21 September 2026 · Checked against 2 independent reference calculations · how PhDino checks its numbers

Estimating the electrical power a small wind turbine produces at a given wind speed.

The power available in moving air scales with the cube of wind speed — double the wind speed, and the power available increases eightfold, not just doubles. That cubic relationship is why a site's average wind speed matters enormously to a wind turbine's output, far more than most people's intuition expects, and why small changes in siting (a slightly higher tower, a clearer approach) can meaningfully change performance.

No turbine captures all the power available in the wind passing through its rotor — the Betz limit is a hard physical ceiling of about 59.3%, since a turbine that extracted 100% of the wind's energy would have to stop the air completely, which would simply block more air from arriving behind it. Real small turbines typically achieve a power coefficient well below that theoretical maximum, due to additional mechanical and electrical losses.

Key formula

Power = 0.5 × air density × swept area × wind speed³ × power coefficient (Cp)
Swept area = π × (rotor diameter ÷ 2)²

Variables

Cp

power coefficient — the fraction of available wind power actually captured, bounded by the Betz limit (≈0.593)

Notes & limitations

• This estimate assumes a single constant wind speed for the whole year, which real sites never actually have — an accurate annual energy estimate needs a full wind speed distribution (a Weibull curve is the standard model) rather than one average number, since the cubic relationship means occasional high-wind periods contribute disproportionately more energy than the average speed alone suggests.
• Small wind turbines are much more site-sensitive than solar panels — turbulence from nearby buildings and trees can both reduce output and increase mechanical wear, which is why wind resource assessment (measuring actual wind at the actual proposed height) matters more here than for solar.