Demand levels rise throughout the day and tend to be highest during a block of hours referred to as "on-peak," which usually occurs between 7:00 a.m. and 10:00 p.m. on weekdays. Weekly patterns: Demand levels are generally lowest between 10 p.m. and 7 a.m. and on weekends.People come home after work and turn up the airconditioning, plug in their electric cars, run their microwaves and televisions. Are you sure peak demand is always during sunlight hours?