Wind power is harnessed through turbines, set on tall towers (typically 20’ or 6m with 10‘ or 3m diameter blades for an individual household's needs) that power a generator that creates electricity.[1][2] They typically require an average of wind speed of 9 mi/hr (14 km/hr) to be worth their investment (as prescribed by the US Department of Energy), and are capable of paying for themselves within their lifetimes. Wind turbines in urban areas usually need to be mounted at least 30’ (10m) in the air to receive enough wind and to be void of nearby obstructions (such as neighboring buildings). Mounting a wind turbine may also require permission from authorities.