Everyday domestic electricity demand can be shown as a load profile 1 which peaks

strongly between 4 and 8 pm. Since most power stations cannot be switched on-line

in an instant, energy providers have to be mindful of this peak and keep some fossil

fuelled power stations ‘running’ so that generators can be quickly powered up. The

carbon impact of this ‘spinning reserve’ can be lowered if the peak demand is

reduced. Appliances such as refrigerators, air conditioners and immersion heaters

cycle on and off for much or all of the day, can under DDC operation, be made to

adjust their cycling during periods of high grid load. Their cycling can be moderated

by a matter of seconds or minutes and, if tuned to the demands of the appliance,

does not unduly affect appliance performance.