Overall, the ionic conductivity of the membrane showed the greatest effect on the performance of the PEMFC. Increasing relative humidity was more favorable than increasing operating temperature with regard to optimizing the system efficiency. In the future work, for the estimation of the system efficiency, it will be necessary to include other BOP components such as pumping power, system control, and stack cooling. In addition, the heat generated in the electrochemical reaction can be utilized for the preheating and humidification. The results obtained from the CFD can be used in a process simulation program such as Aspen Plus. This process simulation can allow predicting not only the power output and system efficiency of the PEMFC, but also the performance and efficiency of the combined heat and power system.