In this study the performance of a commercial air-breathing 100 W Polymer Electrolyte Membrane Fuel Cell (PEMFC) is experimentally investigated through a series of experimental measurements of some of the characteristic outputs of the PEMFC stack such as Voltage and Current by altering the value of the electrical load. The PEMFC used in this project is a commercial product which is called ‘H-100FC’. Additionally, the PEMFC is modelled by using a widely used commercially available generic mathematical model of the Transient System Simulation program (TRNSYS) and the simulation results were compared with the experimental data to investigate the convergence between them and to validate the model in order of establishing confidence in the model when used with rather small FC stacks. A series of interventions for the improvement of the performance of the commercial PEMFC stack is proposed. The Polarization and the Stack Power graphical representations are plotted for the range of the current values of the specific PEMFC. The conclusions coming out of this study show that the model results are in good agreement with the experimental data. Also, stack temperature is proved to be very important for the overall performance and the energy efficiency of the PEMFC stack.