An electric and thermal model of the hybrid system consisting of a photovoltaic-driven alkaline water electrolyzer system is established for hydrogen production. Based on the theory of the thermodynamics and electrochemistry, expression for efficiency of the system is derived. The matching problem between the photovoltaic array and water electrolyzer system is discussed. The efficiency for hydrogen production is optimized by using the method of numerical calculation. Influences of important parameters such as the solar irradiance, the operating temperature of the electrolyzer, efficiencies of the compressor and the regenerator, and band-gap energy of the photovoltaic cell on the efficiency for hydrogen production are analyzed in detail. It is found that the efficiency will achieve its maximum, when the electrolyzer system is operated at the point near the maximum power of the photovoltaic cell. Results obtained here will be helpful for the optimization design and performance improvement of practical photovoltaic driven alkaline water electrolyzer systems. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.