[en] Whereas the French energy policy foresees a share of 50 per cent for nuclear energy in the total electric power production, the shutting down of 14 reactors by 2035, and thus the development of additional renewable and mostly intermittent energies (mainly wind energy), with an evolution of the transport grid, this article reports a study of the cost impact of this policy. It compares investment needs between the scenario proposed by the government and a scenario comprising a lifetime extension of the nuclear fleet up to 60 years or more as it has been proposed in the USA by the NRC (American equivalent of the ASN). Thus, it assesses the cost of the necessary investment in renewable energies, the cost of these new renewable capacities, the cost of network investments, the cost of a reserve force (to deal with intermittency). It states that the lifetime extension of nuclear plants is a good solution, briefly assesses the cost of this lifetime extension, states some remarks about wastes, dismantling, compensations due to EDF, and lifetime extension for the fleet. The comparison then turns in favour of the nuclear option