In this paper, a graphical model of Proton Exchange Membrane (PEM) electrolyser is presented. The modelling is performed with respect to a generic approach then it is tuned regarding the electrolyser considered for the experimental validation. The graphical modelling based on Energetic Macroscopic Representation (EMR) has advantages such as readability, modularity, structural and functional characteristics. The EMR modelling presented here allows the modelling of multi-physics components and highlights the interactions of the electrochemical, thermodynamical, thermal and fluidic phenomena that occur simultaneously in an electrolyser. Generally, in electrolyser models, the temperature is considered as a parameter with different constant values and its influence on other variables of the model is observed. In this paper, the dynamic evolution of the temperature in the stack and the supply water tank is described. The static behaviour of the electrical variables is also studied. To validate the model, a small-scale laboratory electrolyser is used as an experimental tool. The electrical parameters are identified using Matlab/Simulink curves fitting tools. Then, the whole model is simulated. The simulation results fit very well the experimental data. Furthermore, the parameters values of this model are compared to those of the literature and their relevance is pointed out. Using Energetic Macroscopic Representation, the proposed model describes accurately the experimental electrolyser; moreover It can be easily adapted to other electrolysers. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.