This work investigates the techno-economic assessment of a 5 kW micro-cogeneration system based on membrane reactor and PEM fuel cell flexible towards different natural gas qualities. The flexibility of the system is evaluated for four typical natural gas compositions from different European countries featuring an average condition and three extreme cases. The optimal system design conditions are determined together with performance variation as function of NG composition and load. The sweep gas and vacuum pump are explored as options to reduce the membrane surface area, outlining the efficiency advantages of the former (41.21% vs. 39.24%). Simulations at partial load show that the electric efficiency increases until 60-70% of the load in both cases, then quickly drops. Micro-CHP performance are used as input to determine the specific system target cost (sic/kW) based on a yearly energy and economic analysis. The first reveals that the primary energy savings is always positive outlining the environmental benefit of FERRET system application respect to the reference separated production. The target cost considering its application to two dwellings is around 2000 sic/kW. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.