The electricity grid is designed to provide reliable electricity service to all homes and businesses at all times of year. To ensure that whenever you flip a switch in your home that the electricity turns on, the grid has to both produce enough electrons to match the electricity that everyone is using throughout the course of the year as well as enough to power everything that’s turned on at the same time. That second ability–making sure there’s enough power to go around at the times when it’s most needed–is peak demand.