Wind: Fluctuation in time
Gusts, calms and storms: living with a variable source
What this tab covers How availability changes over seconds, days, seasons, years and longer, how predictable it is, and what that means for the plants that use it.Wind is variable at every time scale, from gusts lasting seconds to multi-day calms and stormy seasons. Because power follows the cube of speed, small changes in wind produce large changes in output.
Variation by time scale
| Time scale | What happens | How large |
|---|---|---|
| Seconds to minutes | Gusts and turbulence; smoothed across a large fleet of turbines.2 | A 10% rise in wind speed raises the power in the wind by about 33%, a 10% fall cuts it by about 27% (cube law: 1.1 cubed = 1.33, 0.9 cubed = 0.73). |
| Weather systems (days) | Passing high- and low-pressure systems bring days of strong wind or near calm over whole regions; forecastable a few days ahead.2 | Because of the cube law, a spell at half the usual wind speed carries only one eighth of the usual power. |
| Seasonal | Monthly output follows seasonal wind regimes; the US fleet on average has a period of low production in late summer.9 | Visible in monthly US capacity factors (EIA). |
| Decades (technology) | Taller towers and longer blades reach steadier, faster winds.818 | Global onshore capacity factor rose from 27% in 2010 (2024, IRENA) to 36% in 2025. |
How predictable it is
Wind cannot be scheduled, but weather models forecast it well from hours to a few days ahead, which lets grid operators plan backup and storage. Beyond about a week, only seasonal averages are predictable.
Capacity factors and utilisation
| Plant or measure | Value |
|---|---|
| Onshore wind, new plants worldwide, 2025 | 36%; 27% in 2010 (2024, IRENA)818 |
| Offshore wind, new plants worldwide, 2025 | 41%; 38% in 2010 (2024, IRENA)818 |
| New offshore projects (IEA) | 40-50%6 |
A wind turbine produces something most of the time but runs near full output only in strong winds. Averaged over a year, new onshore turbines produce about 36% of their maximum possible output, and offshore turbines about 41%, because winds at sea are stronger and steadier.
The hardest problem for grids is not gusts, which average out across many turbines, but multi-day lulls when a large weather system covers a whole region. These are forecast days ahead but still need other supply, storage or imports to fill the gap. There is also a seasonal rhythm: the US fleet, for example, produces least in late summer.
Sources
- Power in the wind (power = 1/2 x density x swept area x speed cubed; air density about 1.225 kg/m3) Electrical and Mechanical Services Department, Hong Kong SAR Government (HK RE Net), 2026
- Offshore Wind Outlook 2019 International Energy Agency, 2019
- Renewable Power Generation Costs in 2025 (Executive summary, Figure S1) IRENA, 2026
- Today in Energy: monthly generator capacity factor data now available by fuel and technology US Energy Information Administration, 2014
- Renewable Power Generation Costs in 2024: Summary (Table S1) IRENA, 2025