A control system is a control system that controls transfer of electric power between a power grid and a secondary battery that is mounted in a vehicle and stores electric power for travel and includes a determiner configured to determine whether a state in which charging electric power or discharging electric power is equal to or less than a threshold continues for a predetermined time on the basis of a detection result of the charging electric power with which the secondary battery is charged or the discharging electric power discharged from the secondary battery, and a controller configured to cause the transfer of electric power between the power grid and the secondary battery to stop when the determiner determines that the state in which the charging electric power or the discharging electric power is equal to or less than the threshold continues for the predetermined time.