Abstract: An apparatus for heat recovery by using a heat-pump system comprising an evaporator (14) configured as an air, water and/or earth collector and an internal combustion engine (2) as drive means, the exhaust gases from the internal combustion engine (2) being subjected to post-combustion in a separate post-combustion unit (3). The waste heat from the internal combustion engine (2) and the heat liberated upon post-combustion of the exhaust gases therefrom is supplied to a heat energy carrying medium, especially water of a heating system or the like, which has already been preheaed by the heat-pump system (5, 6). To this end the internal combustion engine (2) and the post-combustion unit (3) have heat exchangers (4, 15) cooperating therewith, respectively. Furthermore, measures are provided (exhaust gas coolers 7, 8, 9) for cooling the exhaust gases escaping to the atmosphere.