A power supply system includes a solar power generator, a storage, a controller, a calculator calculating a predicted amount of electricity consumed and a predicted amount of electricity generated, a calculator calculating a shortage amount that is a difference between the predicted amount of electricity consumed and the predicted amount of electricity generated, and a device setting a predicted amount of electricity stored. In a specified time in which electricity cost is lower than in other times, the controller controls such that the storage is supplied with electricity supplied to a building until an amount of electricity stored reaches the predicted amount of electricity stored. In the other times when an amount of solar power generation is larger than an amount of electricity consumed by an electric load, the controller controls such that the storage stores a surplus of the solar electricity.