The invention relates to a product for heating comprising at least one heating unit (2), which comprises a base material layer with an emission reducing structure on top of said an energy converting structure, combined together to form a selective absorber layer on at least one of the sides of the base material layer, at least one insulation layer (4, 5, 6, 7) of transparent flexible material located on the heating unit (2), which heating unit and the at least one insulation layer on the heating unit (2) of the product (1) are attached to each other air-tightly on the sides such that between at least some of the layers at least one closed air pocket (10, 11) is formed, characterized in that the content to be heated by the product is located below to the base material of the heating unit of the product (1), that temperature of the content of the product (1) will be 90° C.-160° C., as result of the placing the product (1) exposed to radiation of selected wavelengths, and that the energy converting structure in the selective absorber layer has an absorption factor (aS) of a minimum of 0.9 and the emission reducing structure has an emission factor (E) of a maximum of 0.1 and that ratio between the absorption factor (aS) and the emission factor (E) is equal or higher than 9 and that when the selective absorber is exposed to wavelengths ranging from 350 nm to 4000 nm, the energy converting structure converts the wavelengths to thermal energy ranging from 4000 nm to 40.000 nm and the emission of thermal energy is reduced by the emission reducing structure and the contained energy is being used for heating the content of the product (1).