To provide an economical hot-water heat source system capable of extending its life by enhancing stability of a power generating set.

A power load apparatus starting timing adjusting part 37 shifts starting timing of at least one communicable power load apparatus beginning to start so that the total value of the amount of power demand becomes less than the upper threshold value of the power demand determined in advance, based on the incorporated information of the power demand corresponding to the operating situation of the communicable power load apparatuses 17a, 17b, 17c at least connected to the power generating set 1. An intermittently operating apparatus starting timing control part 38 predicts and estimates the starting timing of one or more intermittently operating apparatus which intermittently operates for a predetermined period of time or longer, among the communicable power load apparatuses 17a, 17b, 17c, and when the total value of the amount of the power demand is likely to become less than the lower threshold value of the power demand, it acceleratingly shifts the starting timing of the intermittently operating apparatus by a set time advanced from the predicted and estimated starting time.