In recent years, annual electricity consumption in France amounted to around 470 TWh, 90% being decarbonised; at the same time, oil and natural gas consumption has been around 900 TWh and 450 TWh respectively. At present, electricity accounts for only a quarter of energy consumption. Energy savings alone will not be enough to move away from oil and natural gas: as equally anticipated for Germany and Great Britain, French reliance on electricity will have to increase significantly to replace oil and gas consumption. Various recent projections underestimate this growth. However, erroneous assumptions would affect the security of our energy supply and the daily life of the French people; the impacts on the cost of electricity and energy in general, and on the competitiveness of our economy would be considerable. In this position paper, the National Academy of Technologies of France (NATF) proposes a reasonable assessment of electricity demand in 2050. It points out that the European electricity system will be more vulnerable in coming years. It proposes some principles for the choice of economic data to be used in optimisation models. On the basis of these elements, it highlights some key points for managing change in the electricity system.