The paper develops a methodology to design a practical Multi-sources and Multi- consumers energy management systems (EMS), applicable in particular to transport systems. A global EMS optimization problem is formulated underlining generics criterion and constraints. Remarking that a modularity property is essential to add easily (i.e. without redesigning the whole problem) new energy consumers (or sources), a new EMS structure is presented, splitting the problem into two independent sub-problems. In compensation of sub-optimality, the computing burden is lighten and robustness to energy shortage enhanced. The framework is introduced through the EMS design of an hybrid vehicle transporting conditioned merchandises.