(57) In a method and a device for the recovery of heat of condensation of aqueous vapours in flue gases from the boilers of a district heating plant, in which a steam-driven heat pump is used for the transmission of the heat content of the flue gases to the return water from the consumer circuit before the water is sent back to the boilers, a heat pump is used which has two steps. The first step is operated at a lower temperature than the second step. Discharge steam from the first step is utilized for the operation of the second step. The first step comprises a compressor heat pump driven by a steam expansion engine. The second step comprises a steam jet compressor. There is obtained a comparatively low temperature at the giving-off of the heat of condensation recovered, which is a condition for achieving a high effect factor necessary for obtaining reasonable installation costs.