A power supply system according to the present invention includes a control device (110) which is configured such that if it is predicted that the sum of start-up power for a power generation system (101) and electric power consumed by an external electrical load (105) at start-up of the power generation system (101) and/or the sum of stopped-period power for the power generation system (101) and electric power consumed by the external electrical load (105) at stopping of power generation of the power generation system (101) exceed upper limit power, up to which an electric rate is kept to a relatively low unit price, and that the electric rate is to be changed to a relatively high unit price, then the control device (110) performs control of supplying electric power stored in an electrical storage unit (107) to at least one of the power generation system (101) and the external electrical load (105) in order to prevent the amount of electric power supplied from a power grid (104) from exceeding the upper limit power.