This paper gives a detailed description of the ETEM-SG model, which pro- vides a simulation of the long term development of a multi-energy regional energy system in a smart city environment. The originality of the modeling comes from a representation of the power distribution constraints associated with intermittent and volatile renewable energy sources connected at the transmission network like, e.g. wind farms, or the distribution networks like, e.g. roof top PV panels). The model takes into account the options to optimize the power system provided by grid friendly flexible loads and distributed energy resources, including variable speed drive powered CHP micro-generators, heat pumps, and electric vehicles. One deals with uncertainties in some parameters, by implementing robust optimization techniques. A case study, based on the modeling of the energy system of the “Arc L ́emanique” region shows on simulation results, the importance of introducing a representation of power distribution constraints and options in a regional energy model.