The French national MEGEVH project deals with energy management of hybrid electric vehicles (HEV). The objective is to provide general methodologies to model HEV and optimize their energy flows. The project is subdivided in modeling and optimization sub-projects. Graphical modeling has been chosen to highlight energetic properties of the studied vehicles. Two actual vehicles are taking as reference for the developments. Theoretical methods will be first developed independently of the kind of HEV. Then these methods will be tested on the reference vehicles. The MEGEHV objectives and organization are firstly detailed. In a second section, Energetic Macroscopic Representation of a parallel HEV is described as an example of use of graphical modeling for energy management.