Distribution Network Operators (DNOs) are tasked with getting customers reconnected as soon as possible in the event of a power cut. Generators are needed to provide emergency power if reconnection is not possible in a reasonable amount of time.
For priority customers that might mean a noisy generator on the doorstep to power a stair lift or keep medicines chilled. A large generator could be used to supply a whole property or a number of properties in other cases. The environmental impact of burning fuel in residential or other public locations are major issues alongside generator noise and the cost of re-fuelling.