Energy systems, on which our modern society rely, are in constant transformation. Technological evolution, climate change or the finitude of fossil fuels are some reasons to rethink the centralized, carbon-based energy networks. This way, the design of future energy systems have to take into account multiple concerns, such as local resilience, in addition to technical and economic ones. This paper presents a decision-support tool for the conception of energy systems focusing on the electric vector. The tool was designed using an energy system model implemented in an optimisation algorithm. It takes into account several constraints simultaneously – equilibrium between production and consumption as well as resources availability – and assess the influence of technical parameters on the global performances of the system. An energy system is considered as a combination of production, storage and transport technologies with their operating strategies. The tool’s modularity allows to choose the models adapted to a quick optimisation of energy systems or to an analysis of technical parameters. The second part of the paper presents the optimisation of a local energy system. Search space is composed of production and storage technologies’ number and their operating strategies. Main goals are to find trade-offs between different economic and technical objective-functions – such as levelized cost of energy or local autonomy. Therefore, a genetic algorithm method was used to perform a multi-objective optimisation based on the model. The impact of the operating strategy adopted is underlined.