Cut-in wind speed
The lowest wind speed, measured at hub height, at which a wind turbine starts producing net electrical power, typically 2.5 to 4 m/s for modern machines.
Below the cut-in speed the aerodynamic torque on the rotor is too small to overcome drivetrain friction, generator losses and auxiliary consumption, so the turbine idles or freewheels and may draw a little power from the grid. Once the 10-minute average wind at hub height exceeds cut-in, the controller connects the generator and the turbine begins to climb its power curve.
Typical values:
- Utility-scale onshore turbines (3–7 MW): 2.5–3.5 m/s
- Offshore turbines (8–15 MW): 3–4 m/s
- Small wind turbines (under 50 kW): 2.5–4 m/s, though real-world start-up is often higher because of rotor inertia
Cut-in matters less for energy yield than it appears. Because available power scales with the cube of wind speed, the band between 3 and 4 m/s contains very little energy: at 3.5 m/s a modern rotor produces only 1–3% of rated power. A low cut-in mainly adds operating hours, which helps grid integration and reduces time spent in idle, but rarely shifts annual production by more than 1–2%.
Controllers apply hysteresis around cut-in (for example connect at 3.0 m/s, disconnect at 2.5 m/s) to avoid repeated start-stop cycles that wear the drivetrain and contactors.
Related terms
All terms →- Power curve
The relationship between hub-height wind speed and a turbine's electrical output, used with a wind speed distribution to estimate annual energy production.
- Rated wind speed
The lowest wind speed at which a turbine reaches its nameplate (rated) power output, typically 10 to 13 m/s for modern utility-scale turbines.
- Cut-out wind speed
The wind speed at which a turbine shuts down or ramps down to protect itself from excessive loads, typically 25 m/s (10-minute mean) for utility-scale machines.
- Weibull distribution
A two-parameter probability distribution used to describe how often each wind speed occurs at a site, defined by a scale factor c and a shape factor k.
- Hub height
The height of a wind turbine's rotor centre above ground or sea level; taller hubs reach stronger, steadier winds and are a main driver of rising capacity factors.