# Offshore wind: Efficiency

Same physics as on land, but sea wind gives more

Source page: https://www.materialinsights.org/energy/e_offshore_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.

Offshore turbines face the same 59.3% Betz limit as onshore ones, but stronger and steadier winds at sea give them higher capacity factors: 41% on average for new projects in 2025.

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 that any open rotor can capture |
| **Design power coefficient, IEA 15 MW reference rotor** | 47 to 48.9%^[14](https://www.nrel.gov/docs/fy20osti/75698.pdf) | Commercial | 48.9% of the wind's kinetic energy to rotor shaft power at the design point; about 47% to electricity after the 96.5% efficient generator (calculated) |
| **Global average capacity factor, new projects 2025** | 41%^[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 | Annual electricity generated divided by rated output for a full year; 38% in 2010 (2024, IRENA) |
| **US reference projects, fixed-bottom and floating** | 38.2 to 49%^[3](https://www.nrel.gov/docs/fy25osti/91775.pdf) | Commercial | Net capacity factor; 49.0% fixed-bottom, 38.2% floating (NREL 2023 reference sites) |

#### Where the energy is lost

| Step | Loss |
|---|---|
| **Betz limit: air must keep moving through the rotor** | at least 40.7% of the kinetic energy (calculated)^[1](https://arxiv.org/abs/2010.00982) |
| **Aerodynamic losses at the rotor (drag, tip and wake losses)** | about 10 percentage points (calculated: 59.3% limit against 48.9% design power coefficient)^[1](https://arxiv.org/abs/2010.00982)^[14](https://www.nrel.gov/docs/fy20osti/75698.pdf) |
| **Generator losses in a direct-drive turbine** | about 3.5% of shaft power (calculated from 96.5% generator efficiency)^[14](https://www.nrel.gov/docs/fy20osti/75698.pdf) |

The physics of the rotor is identical on land and at sea. The gain offshore comes from the wind itself: with no hills, trees or buildings to slow it, wind over the sea is faster and less turbulent, and turbines can be made larger because blades and towers do not need to travel by road. Capacity factors rose from 38% in 2010 (2024, IRENA) to 41% in 2025. Some energy is lost again in long export cables and offshore substations before it reaches land.

#### 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. [Definition of the IEA 15-Megawatt Offshore Reference Wind Turbine (NREL/TP-5000-75698)](https://www.nrel.gov/docs/fy20osti/75698.pdf) National Renewable Energy Laboratory, 2020
5. [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_offshore_wind/index.md)
- [Overview](https://www.materialinsights.org/energy/e_offshore_wind/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_offshore_wind/correlation/index.md)
- [Techniques](https://www.materialinsights.org/energy/e_offshore_wind/techniques/index.md)
- [Resources and labour](https://www.materialinsights.org/energy/e_offshore_wind/resources/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_offshore_wind/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_offshore_wind/links/index.md)