[en] This article presents the different notions of cost concerning electricity production. Costs are in fact complex economic data that are designed in the view of the type of decision they will help to settle. Electricity production industry is facing new challenges with the opening of national markets and the stiffening of competition, so decisions about the economic policy of major electricity producers have to be taken carefully and managers require real and valid costs to do so. (A.C.)

[en] The Revue de l'Energie is presenting the most influential French interventions at the 17. Congress of the World Energy Council held in September 1998 in Houston, (USA). These represent only part of French participation in the congress since a total of 16 individuals from France took part in the various sessions. Their presentations cover very varied topics and are one of the things that testify to the interest that our energy industries have in the works and operations of the WEC. Some other figures also bear witness to this interest: 184 French congress members, which is one of the largest delegations after that of the United States, the host country of the congress; 11 technical presentation, covering a wide range of subjects: from the nuclear reactor of the future to the use of bagasse (cane trash) for the production of electricity, from the underground storage of natural gas to the production of extra-heavy crude petroleum. The technical exhibition associated to the Congress was a great success and there again the French presence was able to make its mark: five exhibitors were gathered in the France of 600 m², the most sizeable non-American national area.But French participation in the work of the WEC is not limited to congresses. The French Energy Council [Conseil francais de l'Energie] is careful to ensure its presence both in the formal proceedings of the WEC and within the studies undertaken under its three-year programme. This active French presence is also essential in order to defend the official English-French bilingualism of the World Energy Council. In spite of the good will of the organizers and the support of the general secretary's office in London, the Houston Congress showed how difficult it was to maintain the use of the French language on English-speaking territory. This is a difficult task, one that has to be undertaken anew each time, but one that France and other French-speaking nations have decided to pursue to the end. (authors)