Britain's Daily Electricity Demand
Daily peak, overnight low and the difference between them
The shaded area shows the difference between each day’s lowest and highest electricity demand.
Source: National Energy System Operator Historic Demand Data.
Why does electricity demand fall overnight?
Electricity demand follows a remarkably predictable pattern every day. During the morning and throughout the working day, millions of people are awake, businesses are open, factories are operating, offices are running, and trains, shops and public services all require large amounts of electricity. This creates the high levels of demand seen during the daytime and early evening.
As the evening progresses, businesses close, industrial activity reduces, public transport services become less frequent and most people go to bed. As a result, national electricity demand falls significantly overnight, leaving much of Britain’s electricity generation and network infrastructure underutilised for several hours.
This overnight reduction creates an opportunity. Rather than leaving this spare capacity unused, it can be used for activities that are flexible and do not need to happen during the day. Electric vehicles can charge overnight, hot water cylinders can be heated while demand is low, and heat pumps can warm homes before people wake up, reducing the amount of electricity required during the morning peak in winter.
Making better use of this overnight capacity benefits everyone. It improves utilisation of power stations, renewable generation, batteries and electricity networks that have already been built, while reducing pressure during the busiest parts of the day. This is why lower overnight electricity prices make economic sense: they encourage demand to move to the hours when the electricity system has the greatest spare capacity, making the entire network more efficient without reducing the quality of service for consumers.