The development of hybrid systems is a competitive solution to achieve energy decarbonization. The use of complementary sources such as solar and wind energy allows high system reliability. The time lag between energy demand and generation can be reduced by using storage systems. A multi-objective optimization method for sizing hybrid power generation systems for districts has been proposed in order to identify efficient, cost-effective and least environmental impact solutions, depending on the context in which the system is located. The analysis allows to identify the most appropriate power ratings of each component. The goal is to improve the reliability of these systems to achieve energy autonomy in the future, autonomy is intended to minimize as much as possible the exchanges with the network. The method can be easily applied to a grid-connected (GC) or stand-alone (SA) PV-W system, with or without battery storage, in any climatic context and load condition. Dynamic and parametric simulations and optimizations have been performed. The energy reliability method (ERC) allows to choose the most appropriate combination of indicators to be constrained or optimized according to the specific application.