This work presents a thermodynamic analysis of on-board hydrogen generation from ethanol steam reforming for use in vehicles equipped with internal combustion engines. Ethanol is considered a liquid hydrogen carrier, with advantages related to availability, ambient-condition storage and Brazil s existing biofuel distribution infrastructure. The model was implemented in MATLAB using Gibbs free energy minimization to estimate the equilibrium composition of the reformate gas for different temperatures and steam/ethanol ratios. Hydrogen relative yield, by-product formation, the reformer thermal balance and the equivalent electrical energy associated with the produced H2 were also evaluated. For the base case (T = 900 K and S/E = 6.0) the routine estimated 4.913 mol H2 per mol of ethanol fed, corresponding to a relative yield of 81.88 percent. The highest H2 production within the simulated domain occurred near 900 K and S/E = 10, although this condition requires larger preheating thermal demand. From the reformate composition and calculated energy balances, the useful energy converted by each end device was estimated: the PEMFC showed an equivalent electrical efficiency of ≈ 28.2 percent, the internal combustion engine converted roughly 42.3 percent of the useful energetic content into mechanical work, and the SOFC reached the highest conversion efficiency at about 72.6 percent. It is concluded that ethanol steam reforming integrated with exhaust heat recovery is a promising alternative to increase the overall efficiency of vehicles with internal combustion engines and to reduce reliance on compressed hydrogen stored on board; the final choice of conversion technology (PEMFC, SOFC or engine) is decisive for the reformer s optimal operating point.