This study focuses on the multiphysics modelling of a classical alkaline water electrolyzer (AWE). An Euler–Euler two-fluid model is solved in addition to current conservation equations to tackle the problem. The objective is to investigate the effect of gas generation on the V–I characteristics of the system. The model is validated by comparing the model predicted V–I characteristics with available experimental data at different temperatures in a classical AWE. The study reveals that presence of gas increases over potential and reduces the current density. A special case with corrugated electrode is tested using validated model, and results are compared. Results indicate that these modification on electrode surface reduces the electrolyzer performance and current density which ultimately reduces hydrogen production rate. Hence it is essential that the electrodes are free of surface defects.