The load factor of wind turbines has a strong effect on the wider electricity system. As the rated wind speed of turbines reduces, the load factor increases. This allows wind farms to generate constant power for longer periods of time, which in turn improves the match between the profiles of electricity demand and renewable generation and reduces the need for energy storage. The behaviour of the total cost of electricity is driven largely by the levelized cost of wind power, which has a minimum at a rated speed of 12 m/s. Faster rated speeds (>12 m/s) lead to higher electricity costs due to the lower load factors of the turbines. At slower rated speeds (<12 m/s) the higher capital cost of the turbines overshadows the improved load factors, leading to increased electricity costs.