A power supply control system, which has a power-generating equipment and a power-storing device, comprising: a power storage level detector configured to detect a remaining level of the power-storing device; a computing unit; and a controller, wherein the computing unit performs steps of: computing a prospective power generation of the power-generating equipment until a predetermined operation time and a prospective load power consumption of the connected load until the predetermined operation time; computing dischargeable time of the power-storing device until the remaining level reaches the minimum level based upon the prospective power generation, the prospective load power consumption and the remaining level detected by the remaining level detector; computing an average power generation output of the power-generating equipment and an average load power consumption of the load; and computing a power generation reaching time until the average power generation output reaches the average load power consumption, characterized in that the controller controls, in the case that the dischargeable time computed by the computing unit is shorter than the power generation reaching time and equal to or shorter than the predetermined operation time, to reduce power consumption of the connected load. a power storage level detector configured to detect a remaining level of the power-storing device; a computing unit; and a controller, wherein the computing unit performs steps of: computing a prospective power generation of the power-generating equipment until a predetermined operation time and a prospective load power consumption of the connected load until the predetermined operation time; computing dischargeable time of the power-storing device until the remaining level reaches the minimum level based upon the prospective power generation, the prospective load power consumption and the remaining level detected by the remaining level detector; computing an average power generation output of the power-generating equipment and an average load power consumption of the load; and computing a power generation reaching time until the average power generation output reaches the average load power consumption, characterized in that the controller controls, in the case that the dischargeable time computed by the computing unit is shorter than the power generation reaching time and equal to or shorter than the predetermined operation time, to reduce power consumption of the connected load. computing a prospective power generation of the power-generating equipment until a predetermined operation time and a prospective load power consumption of the connected load until the predetermined operation time; computing dischargeable time of the power-storing device until the remaining level reaches the minimum level based upon the prospective power generation, the prospective load power consumption and the remaining level detected by the remaining level detector; computing an average power generation output of the power-generating equipment and an average load power consumption of the load; and computing a power generation reaching time until the average power generation output reaches the average load power consumption, characterized in that the controller controls, in the case that the dischargeable time computed by the computing unit is shorter than the power generation reaching time and equal to or shorter than the predetermined operation time, to reduce power consumption of the connected load.