This book contains plenty of data, tables and figures, required for beginning to analyse data, which could not be done without first establishing what data are. After presenting the main sources of data, this chapter will briefly present the models required to define the potential energy future. It will explore the required indicators to both evaluate future tendencies of energy consumption and to take action today. A significant part of the chapter is then dedicated to past, present and future, global and European energy consumption. This will be formulated for primary energies, final energies and in particular related to electricity consumption.