The methodology used to assess shadow flicker (caused when rotating wind turbine blades periodically cast shadows over neighbouring properties as they turn) is set out in the  Department of Energy and Climate Change (DECC) (2011) document as well as various pieces of national legislation. 

Generally, the impacts of shadow flicker are considered not to adversely impact properties which are greater than 10 rotor diameters from a wind turbine. However, this will depend on the location of the wind turbine in relation to the properties, as if it is on more elevated ground then there is the possibility that longer shadows could be cast.Any properties within 10 rotor diameters will need to be comprehensively assessed and modelled to identify the number of hours of shadow flicker that may occur. Some councils require properties outside the 10 rotor diameter radius to also be assessed.