Polymer electrolyte membrane (PEM) water electrolysis generates 'green' hydrogen when conducted with electricity from renewable-but fluctuating-sources like wind or solar photovoltaic. Unfortunately, the long-term stability of the electrolyzer performance is still not fully understood under these input power profiles. In this study, we contrast the degradation behavior of our PEM water electrolysis single cells that occurs under operation with constant and intermittent power and derive preferable operating states. For this purpose, five different current density profiles are used, of which two were constant and three dynamic. Cells operated at 1 A cm(-2) show no degradation. However, degradation was observed for the remaining four profiles, all of which underwent periods of high current density (2 A cm(-2)). Hereby, constant operation at 2 A cm(-2) led to the highest degradation rate (194 mu V h(-1)). Degradation can be greatly reduced when the cells are operated with an intermittent profile. Current density switching has a positive effect on durability, as it causes reversible parts of degradation to recover and results in a substantially reduced degradation per mole of hydrogen produced. Two general degradation phenomena were identified, a decreased anode exchange current density and an increased contact resistance at the titanium porous transport layer (Ti-PTL). (C) 2016 Elsevier B.V. All rights reserved.