[en] This study attempts to give a summarised vision of the concept of eternality in energy production, the social and economic usefulness of its evaluation and consideration as support to the political decision-marking in environmental regulation matters, technologies selection of new plants, priorities establishment on energy plans, etc. More relevant environmental externalisation are described, as are the effects on the health, ecosystems, materials and climate, as well as some of the socioeconomic externalisation such as the employment, increase of the GDP and the reduction and depletion of energy resources. Different methodologies used during the last years have been reviewed as well as the principals resulted obtained in the most relevant studies accomplished internationally on this topic. Special mention has deserved the European study National Implementation of the Extern E Methodology in the EU^. Results obtained are represented in Table 2 of this study. Also they are exposed, in a summarised way, the results obtained in the evaluation of environmental externalisation of the Spanish electrical system in function of the fuel cycle. In this last case the obtained results are more approximated since have been obtained by extrapolation from the obtained for ten representative plants geographically distributed trough the Peninsula. Finally it has been analysed the influence that the internalization of the external costs of conventional energies can have in the competitiveness and in te market of renewable energy, those which originate less environmental effects and therefore produce much smaller external costs. The mechanisms of internalization and the consideration on the convenience or not of their incorporation in the price of energy have been also discussed. (Author) 30 refs