The term TOU is an abbreviation for Time-of-Use metering. TOU metering is different form normal meters in terms that its measures how much electricity is consumed as well as it measures when electricity was consumed.
By application of TOU specially-developed rate tariffs that price demand and energy at different rates during specified time periods throughout the day loads can be managed effectively.
During the time when utilities want to reduce their load (technically known as peak load hours), for example time during mid-afternoon, the power charges are set higher than off-peak hours.
TOU tariffs are becoming quite popular recently. The practical implementation of TOU tariffs are easy to be implemented using microprocessor chips and digital metering equipment.
See below Time of use rates: