Hydrogen production from a multifunctional microdevice consisting of thermally coupled catalytic plate combustion and reforming microreactors is simulated for methane and methanol reforming as representatives of a high and a low temperature process, respectively. Both reforming processes are feasible at microscales with high conversions over a wide combustible and reforming stream inlet velocity range, and can be tuned to provide variable power output. Interestingly, in low temperature reforming, the fraction of heat release that is wasted, as "excess enthalpy" in the products, is not significantly lower than in high temperature reforming at the breakthrough limit. Along the breakthrough line, more than 30% higher power efficiency to hydrogen is predicted for the methanol system due to the high CO2:CO ratio. Finally, matching the reaction zones in the two channels via proper choice of catalyst loadings and channel gap sizes can alleviate hot spots and axial temperature gradients promoted by low conductivity materials. (C) 2009 Elsevier Ltd. All rights reserved.