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