An electric power control method for an electric power load and an electric power storage device including assigning one of a peak shaving control or other services to at least one of time slots that are divided by a specific time unit, obtaining a consumption power of the electric power load of each of the time slots, determining power-purchase electric power according to the consumption power of each of the time slots, restricting a consumption power of the electric power load at one or more peak slots where the consumption power of the electric power load is more than or equal to a target power-purchase electric power upper limit, restricting the restricted consumption power of the electric power load and discharging the electric power storage device at one or more peak slots if the restricted consumption power of the electric power load is more than or equal to a target power-purchase electric power upper limit and the peak shaving is assigned.