A cup anemometer is usually used to measure wind speeds. The cup anemometer is composed of a vertical axis and three cups capturing the wind. The number of revolutions per minute is registered electronically. The anemometer is usually associated with a wind vane which can determine the wind direction. Instead of cups, some anemometers are fitted with propellers, but the cup anemometer is the most common type. Laser or ultrasonic anemometers can also be seen. They measure the wind by detecting the phase shifting of sound or coherent light reflected from the air molecules. Hot wire anemometers detect the wind speed through minute temperature differences between wires placed in the wind and in the wind shade.

The main advantage of non-mechanical anemometers is that they are less sensitive to icing. Nevertheless, cup anemometers are generally used everywhere. In areas where icing is likely, special models with electrical heating are available. But they may require a connection to the grid. 

Good quality anemometers are essential for wind resource estimation on a site. Cheap anemometers can be sufficient for meteorology (low level of accuracy is required) but they are generally insufficient for wind speed measurements for a site inspection. The measurement error can reach 5 to 10 percent, which is unacceptable for such measurements. Indeed, a 10% error in the wind speed measurement will lead to an error of 33% for the energy production estimation, which would be disastrous for the economy of the project. These cheap anemometers can also be used on top of wind turbines to determine whether the wind is strong enough to allow the start of the turbine.

A high quality anemometer must have a measurement error around 1% and be well calibrated. Their price varies around 700 and 1000 US dollars, which is negligible in comparison with the potential loss generated by a wrong measurement.

Sensors for air pressure and temperature can also be installed in order to calculated the air density, an essential parameter for the calculation of the energy production of the turbine. Additional sensors can be added according to the requirements of the site: sensors for humidity, to detect when icing is likely, rain sensors, etc…