The invention relates to a melting unit and method in which: a melting chamber is heated by means of combustion, the combustion fumes are used to heat the air used as a heat-transfer gas, the heated air is used to pre-heat the combustion oxygen and/or the gaseous fuel, the tempered air resulting from the pre-heating is compressed, the compressed tempered air is heated by means of heat exchange with the combustion fumes, and the mechanical and/or electrical energy is generated by expansion of the heated compressed air.