BESS are one of the most efficient technologies in the electricity production chain. Indeed, they make it possible to avoid waste and make full use of the potential of renewable sources and the distribution grid. They have also experienced remarkable technological development. Over the past decade, the prices of the batteries they use have fallen by almost 90%, while their energy density, that is, the amount of energy stored relative to mass, has increased by more than 50%. They are also highly safe systems.