A power supply control system includes a remaining level detector 22 of a power-storing device 20; and an estimate computing unit 42 which estimates a prospective power generation of power-generating equipment 10 and a prospective load power consumption of connected loads, and thus, based thereupon and remaining level, a dischargeable time until remaining level reaches the minimum level, and computes an average power generation output of a power-generating equipment 10 and an average load power consumption connected loads 101-105, and thus power generation reaching time until the average power generation output reaches the average load power consumption; and a controller 43 which controls, if the dischargeable time is shorter than the power generation reaching time, to reduce power consumption of the connected loads 101-105.