ABSTRACT
To reduce needs in energy, the “efficiency” lever wins unanimous support since it means consuming less for an equal service thanks to technology. The best example is certainly home insulation. One should keep in mind that there are physical limits to efficiency. Energy efficiency can also consist in trying to reuse stored energy. Significant advances in energy efficiency have been achieved following the 1974 and 1979 oil crises. As a consequence, the average consumption of vehicles has measurably dropped in 40 years thanks to more efficient engines. However, today the consumption of vehicles hardly decreases any more. Every year, in Australia, a World Solar Challenge is organized, which a race between cars is running on solar energy. Energy sobriety, which consists in giving priority to the most useful uses of energy, “restraining the most extravagant and eliminating harmful ones”, supposes a definition of the uses that are useful or harmful.
