Onshore wind: Efficiency
The law of physics that caps every turbine at 59.3%
What this tab covers How much of the energy available is actually captured or extracted, in per cent: theoretical limits, laboratory records, typical new equipment and in-service averages, each with exactly what is being measured.A turbine can never extract more than 59.3% of the kinetic energy in the wind passing through its rotor (the Betz limit). Modern turbines reach about 40-50% between their start-up and rated wind speeds, but over a year they deliver about a third of their rated output because the wind varies.
Chart: Efficiency ranges
Theoretical limit Commercial In serviceEfficiency by measure
| Measure | Range | Type | What is measured |
|---|---|---|---|
| Betz limit | 59.3%1 | Theoretical limit | Maximum share of the wind's kinetic energy through the rotor area that any open rotor can capture |
| Power coefficient, modern large turbines | 40 to 50%1 | Commercial | Wind kinetic energy through the rotor to electricity, between cut-in and rated wind speed (about 67-84% of the Betz limit, calculated) |
| Global average capacity factor, new projects 2025 | 36%215 | In service | Electricity actually generated over a year divided by output at full rated power all year; 27% in 2010 (2024, IRENA) |
| US reference project capacity factor | 46.9%3 | Commercial | Net capacity factor of NREL's 2023 land-based reference project on a good US site |
Where the energy is lost
| Step | Loss |
|---|---|
| Air must keep flowing out behind the rotor, so it cannot be stopped completely | at least 40.7% of the kinetic energy (calculated from the Betz limit)1 |
| Blade drag, wake rotation and tip losses, plus gearbox, generator and converter losses | brings the 59.3% ceiling down to about 40-50%1 |
Two different numbers matter. The power coefficient is how much of the wind's energy the rotor turns into electricity at a given moment; physics limits it to 59.3%, and modern machines come within about 10-20 percentage points of that. The capacity factor measures how hard the turbine works over a year: wind speed varies, and above a cut-out speed the turbine stops to protect itself. The global average for new onshore projects rose from 27% in 2010 (2024, IRENA) to 36% in 2025 (IRENA), mainly because taller towers and longer blades reach steadier winds.
Sources
- Physical limits of wind energy within the atmosphere and its use as renewable energy: from the theoretical basis to practical implications (Kleidon, Meteorologische Zeitschrift 30(3)) arXiv (author manuscript of peer-reviewed paper), 2021
- Renewable Power Generation Costs in 2025 (Executive summary, Figure S1) IRENA, 2026
- Cost of Wind Energy Review: 2024 Edition (NREL/PR-5000-91775), reference projects in 2023 USD National Renewable Energy Laboratory, 2025
- Renewable Power Generation Costs in 2024: Summary (Table S1) IRENA, 2025