Wind Air Density Correction

Linearly: P = ½ρAv³Cp. Thin air at 800 m altitude on a 45°C afternoon carries ~12% less mass — and exactly that much less power at the same wind speed. Density explains most 'mysterious' summer underperformance before any hardware gets blamed.

Compute it from altitude and a representative temperature (this tool) — or better, log it hourly from site pressure/temperature sensors. Annual averages hide the seasonal swing: the same site spans ~8% density between winter mornings and summer afternoons.

Yes — OEM curves are stated at 1.225 kg/m³ (15°C, sea level). IEC 61400-12 requires density-normalizing measured data before comparison. Verifying a turbine against its curve without the correction produces false failures every summer and false praise every winter.

Marginally — humid air is slightly LESS dense (water vapor is lighter than N₂/O₂), but the effect is under 1.5% even in tropical conditions. Temperature and altitude do the heavy lifting; ignore humidity for screening, include it only in formal power-performance tests.