PROBLEM TO BE SOLVED: To provide a hot water supply system capable of easily and appropriately attaching an exhaust cover to a front surface of a front cover by means having a simple structure even if a flange or the like is not formed in an upper surface portion of an exterior case.SOLUTION: A hot water supply system A comprises a fixture 2 for attaching an exhaust cover 3 to a front cover 10 of an exterior case 1. The fixture 2 includes: a first engagement portion 21 that is engageable with an upper edge portion of the front cover 10 so that this fixture 2 is set in a state of being suspended from the upper edge portion, and upper movement of which is restricted by a top plate 13 attached to an upper side of the front cover 10; and a second engagement portion 22 that is engageable with a side edge portion of the front cover 10 so as to restrict a position of the fixture 2 in longitudinal and lateral width directions of the front cover 10.
