Many electricity providers offer their customers time sensitive, or time of use, pricing plans. These plans reflect the actual cost of producing electricity at the time it is needed. They are designed to encourage customers to lower their electricity use during times when the cost of producing electricity is high. People and businesses use varying amounts of electricity throughout the day and power utilities adjust to these changing demands. When demand is low, utilities can supply electricity using less expensive sources, but when demand is high more expensive sources must be added to supply enough electricity