Significant research efforts have been invested in the automotive industry on hybrid-electrified powertrains in order to reduce the passenger cars’ dependence on oil. Powertrains electrification resulted in a wide range of hybrid vehicle architectures. Fuel consumption of these powertrains strongly relies on the energy converter performance, as well as on the energy management strategy deployed on-board. This paper investigates the potential of energy consumption savings of a serial hybrid electric vehicle (SHEV) using an hydrogen PEM fuel cell (PEMFC) as energy converter instead of the conventional internal combustion engine (ICE). A PEMFC model was developed and thermodynamic system efficiency was simulated. A SHEV model is developed and powertrain components are sized considering vehicle performance criteria. Energy consumption simulations are performed on WLTP cycle using dynamic programing as global optimal energy management strategy. Results show improved efficiency with PEMFC as auxiliary power unit (APU) compared to ICE. Moreover, PEMFC offers other intrinsic advantages such low noise and vibration, suitable vehicle integration as well as a zero CO2 tank to wheel emissions. The production of clean hydrogen is also discussed in this paper. Consequently, the studied PEM-APU presents a potential for implementation on SHEVs.