The invention relates to a heating system with recovery of waste water heat that includes a heat pump, a waste water holding vat (10) that includes a casing (34), defining an internal space (36) for holding the waste water, and a heat exchanger (26, 28) for recovering calories in the holding vat (10) and using them in the heat pump. The holding vat (10) includes at least one baffle (44) that extends into the holding space (36), divides the holding vat (10) into a plurality of compartments (46), and defines, with the casing (34), a waste water flow path that bypasses the baffle(s) (44) and passes into the compartments (46). The heat exchanger (26, 28) is arranged so as to recover calories in at least two compartments (46).
