An energy cable comprising at least one cable core comprising an electric conductor, a crosslinked electrically insulating system comprising an inner semiconducting layer, an insulating layer and an outer semiconducting layer and zeolite particles placed between the electric conductor and the inner semiconducting layer of the insulating system. The zeolite particles are able to efficiently extract and irreversibly absorb the by-products deriving from the cross-linking reaction, so as to avoid space charge accumulation in the insulating material during cable lifespan. This allows to eliminate the high temperature, long lasting degassing process of the energy cable cores having a crosslinked insulating layer, or at least to reduce temperature and/or duration of the same, so as to increase productivity and reduce manufacturing costs.