The energy demand of ICT (Information and Communica-tions Technology) may be considered as an important topic of the 21st century. Today, at a country level, for example in France, there is a lack of credible estimates concerning ICT energy demand and concerning its evolution in particular in terms of network equipments. Our PhD work may be a con-tribution to the know-how on this topic. In this paper, we give first an overview of our study's framework. In a second time, we focus our investigations on a quantitative analysis and its results. In a third time we give a description of the energy model of the networks which is designed by FTR&D.