The present invention relates to a heating assembly (10) of an aerosol-generating device for heating aerosol-forming substrate. The heating assembly comprises a chemical heating device (200) configured to generate primary heat by an exothermic chemical reaction and to supply the primary heat to an aerosol-forming substrate for heating the substrate. The heating assembly further comprises an electrical heating device (100) configured to electrically generate and supply secondary heat to the aerosol-forming substrate for heating the substrate. The invention further relates to an aerosol-generating device including such a heating assembly. A method for generating an aerosol by heating aerosol-forming substrate comprises at least one of a sequential or a parallel performance of the following steps: generating primary heat by an exothermic chemical reaction and supplying the primary heat to the aerosol-forming substrate for heating the substrate; and electrically generating secondary heat and supplying the secondary heat to the aerosol-forming substrate for further heating the substrate.