# Onshore wind: Efficiency

The law of physics that caps every turbine at 59.3%

Source page: https://www.materialinsights.org/energy/e_onshore_wind/efficiency/

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 service

#### Efficiency by measure

| Measure | Range | Type | What is measured |
|---|---|---|---|
| **Betz limit** | 59.3%^[1](https://arxiv.org/abs/2010.00982) | 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](https://arxiv.org/abs/2010.00982) | 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%^[2](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2026/Jul/IRENA_TEC_RPGC_in_2025_2026.pdf)^[15](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Jul/IRENA_TEC_RPGC_in_2024_Summary_2025.pdf) | 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](https://www.nrel.gov/docs/fy25osti/91775.pdf) | 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](https://arxiv.org/abs/2010.00982) |
| **Blade drag, wake rotation and tip losses, plus gearbox, generator and converter losses** | brings the 59.3% ceiling down to about 40-50%^[1](https://arxiv.org/abs/2010.00982) |

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

1. [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))](https://arxiv.org/abs/2010.00982) arXiv (author manuscript of peer-reviewed paper), 2021
2. [Renewable Power Generation Costs in 2025 (Executive summary, Figure S1)](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2026/Jul/IRENA_TEC_RPGC_in_2025_2026.pdf) IRENA, 2026
3. [Cost of Wind Energy Review: 2024 Edition (NREL/PR-5000-91775), reference projects in 2023 USD](https://www.nrel.gov/docs/fy25osti/91775.pdf) National Renewable Energy Laboratory, 2025
4. [Renewable Power Generation Costs in 2024: Summary (Table S1)](https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2025/Jul/IRENA_TEC_RPGC_in_2024_Summary_2025.pdf) IRENA, 2025

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_onshore_wind/index.md)
- [Overview](https://www.materialinsights.org/energy/e_onshore_wind/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_onshore_wind/correlation/index.md)
- [Techniques](https://www.materialinsights.org/energy/e_onshore_wind/techniques/index.md)
- [Resources and labour](https://www.materialinsights.org/energy/e_onshore_wind/resources/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_onshore_wind/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_onshore_wind/links/index.md)