The volumetric entropy generation rate distributions and exergy losses of premixed methane/air with hydrogen addition in a micro-planar combustor were numerically investigated. Detailed reaction mechanism for methane/hydrogen/air was considered. The analysis identified reactions contributing most of the entropy generated in combustion. The entropy generation rates due to the effects of chemical reaction, thermal conduction and mass diffusion are calculated based on the gas properties. A detailed parametric study of the influence of flow velocity and hydrogen mass fraction on the volumetric entropy generation rate is performed. With the increase of H-2 addition to methane fuel, the entropy generation rates induced by thermal conduction and mass diffusion decrease, however, the chemical reaction induced entropy generation rate is less sensitive to H-2 addition. The total entropy generation rate rises with the inlet velocity. The availability reduction by wall heat losses increases with increasing H-2 addition and inlet velocity. The exergy efficiency remains nearly constant with H-2 addition. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.