This work presents a simulative energy efficiency analysis performed on fuel processor PEMFC systems, considering methane as fuel and steam reforming or autothermal reforming as processes to produce hydrogen. Computation of energy efficiency takes into account the power required by the auxiliary units, coupling of the fuel processor with the fuel cell as well as heat recovery and integration. Two system configurations were simulated and compared: an innovative configuration, based on an integrated membrane reactor directly coupled with the fuel cell, and a conventional configuration, based on a classic reforming reactor followed by a conventional CO clean-up section, constituted by water gas shift and preferential CO oxidation reactors. Reforming temperature, plant pressure, steam to methane and oxygen to methane inlet ratios were considered as process parameters. The effect of the addition of steam as sweep gas is also presented and discussed. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.