A microwave heating device includes at least two radiating portions that are adapted to radiate microwaves to the heating chamber and can be operated according to a plurality of operational configurations that differ in frequency and/or in phase shift(s) between the radiated microwaves. Data of energy efficiency, as a function of operational configurations, can be obtained for a product in the heating chamber. For example, energy efficiency data are obtained through a learning procedure. The obtained data can be processed to select one or more operational configurations ranking high in energy efficiency and a heating procedure for the product inside the heating chamber can be executed by operating the at least two radiating portions according to the selected one or more operational configurations.