In light of the emergence of non-conventional sources of energy, new technologies as well as geopolitical fluctuations, energy price forecasts have been revised with all what it means in terms of significant impact on the price level. In addition, the need to address global warming and to review energy production patterns in order to promote the use of renewable energies has been addressed. In this context, as stressed by Jean-Marie Chevalier, it is very hard to determine the trends in energy price evolution or to predict the transformation in energy production systems. Chevalier demonstrates many factors (and actors) involved in the evolution of energy prices and systems and highlights the key elements that will play either a leading or a restraining role in this evolution in both the medium and long terms.