Small wind turbines convert wind energy into electricity for off-grid and grid-connected homesteads. A wind turbine consists of blades, a [[Generators]] or alternator, a tower, and a charge controller or inverter. Wind power is most practical in locations with average wind speeds of 5 meters per second (11 miles per hour) or greater at hub height. Unlike solar, wind can produce power at night and during cloudy weather, making it a complementary energy source in many locations.
Horizontal-axis wind turbines are the most common design. The rotor faces into the wind, and the generator is mounted at the top of the tower. Small horizontal-axis turbines range from 400 watts to 20 kilowatts. They require a yaw mechanism to keep the rotor facing the wind and a furling mechanism to protect the turbine in high winds.
Vertical-axis wind turbines (VAWTs) have a vertical rotor shaft and accept wind from any direction without a yaw mechanism. They are simpler and easier to maintain than horizontal-axis turbines but are less efficient at converting wind energy. VAWTs are used in turbulent wind conditions and urban environments.
The tower is the most critical structural component. Tower height significantly affects energy production because wind speed increases with height. A tower height of 18 to 30 meters (60 to 100 feet) is typical for small turbines. Tower types include guyed lattice towers, freestanding towers, and tilt-up towers that can be raised and lowered for maintenance.
A turbine is sited at least 200 meters (600 feet) from obstacles and at a hub height at least 10 meters (30 feet) above any surrounding obstructions within 100 meters. Energy production is proportional to the cube of wind speed, so a 10 percent increase in wind speed produces a 33 percent increase in energy. A 1.5 kilowatt turbine in a 5 m/s average wind site produces approximately 2,000 to 3,000 kilowatt-hours per year.