Abstract In this paper, a performance analysis on the basis of a simulation model and experimental data of a 1kW High Temperature PEM (HTPEM) cogeneration system is presented. The system is composed of a steam reforming unit that can be operated with natural gas. The balance of plant is modeled using a commercial industrial process simulation software, Aspen Plus®. Components such as burner and chemical reactors are simulated using existing modules available in the software library. The fuel cell performance is predicted by means of a zero dimensional semi-empirical model implemented in Fortran and then integrated in the Aspen Plus process simulation. The fuel cell model is validated using experimental data available in the literature and from tests carried out by the authors. The aim of the work is to perform an energy analysis that allows investigating system partial load operations and to assess the difference with Low Temperature PEM (LTPEM) fuel cell based systems. Results show that HTPEM systems could achieve electrical efficiencies similar to LTPEM systems but with a simpler balance of plant.