Solid polymer electrolyte (SPE) water electrolysis is analyzed by a simple model based on Butler-Volmer kinetics for electrodes and transport resistance in the polymer electrolyte. An equivalent electrical circuit analogy is provided for the sequential kinetic and transport resistances. The model provides a relation between applied terminal voltage of the electrolysis cell and current density in terms of Nernst potential, exchange current densities, and conductivity of polymer electrolyte. The overpotentials and resistances at the anode, cathode, and overpotential due to ohmic resistances are individually analyzed and are in good agreement with experimental results. The reduction kinetics at the cathode is relatively fast while the anodic overpotential is mainly responsible for the voltage drop. (C) 2004 Elsevier B.V. All rights reserved.