This research investigates the optimal sizing of the Energy Storage System (ESS) for Plug-in Fuel Cell Electric Vehicles (PFCEVs), taking into account technical, economic, and environmental challenges. The primary goal is to minimize both life cycle costs (LCC) and operational costs while simultaneously reducing CO2 emissions and preserving the durability of the power system. The PFCEV’s ESS comprises three core components: a battery, a proton-exchange membrane fuel cell (FC) system, and a supercapacitor (SC). Performance evaluation involves strict constraints on the vehicle’s operational parameters, and simulations are conducted following the Urban Dynamometer Driving Schedule (UDDS). A notable contribution of this research is the implementation of a double-loop optimization technique using quadratic programming (QP) and a genetic algorithm (GA) to identify a feasible solution space that respects the specified constraints. In summary, the findings yield valuable insights and recommendations for the optimal sizing of PFCEV ESS. The comparative analysis conducted between different PFCEVs, Fuel Cell Vehicles (FCVs), and Battery Electric Vehicles (BEVs), reveals that PFCEVs demonstrate distinct advantages. Finally, a sensitivity analysis concerning various hydrogen types shows a need for cost reduction in producing green hydrogen to improve its economic feasibility and operational efficiency.