The maximum exploitation of local renewable energy sources is a key feature of DG (Distributed Generation) systems: to this aim, HPSs (Hybrid Power Systems), integrating renewable and non-renewable power sources with local energy storage may represent an effective solution, although they may require an optimum utilization of the different sub-systems, for example if including FCs (Fuel Cells). This work introduces a new definition of system efficiency, which is linked to a class index defined according to the local renewable energy availability. The system efficiency is also demonstrated as a function of two performance parameters describing the effectiveness, respectively, of renewable and fossil energy conversion. The new set of parameters is used to study an experimental DG hybrid system including photovoltaic panels and FCs, representing a detached house. A test facility has been used to validate numerical models. A full year period was then simulated, to single out that the new set of parameters could help evaluate the HPS environmental performance and the effective renewable energy exploitation; the class index also helps evaluating the real system efficiency and environmental performance, which strongly depends on the local renewable energy available. An optimal management strategy is also found respect to the FCs utilization. (C) 2014 Elsevier Ltd. All rights reserved.