A composite Nafion-Sulfated Zirconia (SZrO2) membrane was prepared and investigated in a solid polymer electrolyte (SPE) water electrolyzer at different temperatures. The performance was compared to a commercial Nafion 115 membrane of similar thickness. The cell equipped with Nafion - SZrO2 showed better performance at intermediate temperatures. The current densities were 2.7 and 2.2 A.cm(2) at a terminal voltage of 1.8 V for the composite Nafion - SZrO2 and Nafion 115, respectively, at 100 degrees C and atmospheric pressure. The superior performance of the composite electrolyte was due to the strong acidity and water affinity of sulfated zirconia nanoparticles used as filler. Operation at intermediate temperatures in a solid polymer electrolyte water electrolyzer appears useful for a better thermal management of the heat released at high current densities.