The relationship between the electric current fluctuation and the efficiency of Alkaline Water Electrolysis (AWE) was analyzed and the results are presented in this paper. Square, triangle, sine and sawtooth current waveforms with various frequency and amplitude settings were applied to a lab scale electrolyser with current densities up to 5000 A/m(2). A novel, fully automatic measurement and data acquisition system was designed in order to generate thousands of experiments in a short period of time. The results show that non steady DC current applied to the cell cause efficiency loss compared to the steady DC condition at same current density. Furthermore, the efficiency loss can be influenced by 3 parameters of the fluctuating electric current: ripple factor, frequency and mean current density. The detailed results give new insight for the investigation of water electrolysis efficiency. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.