This study investigates the incorporation of renewable energy sources into microgrids, with a focus on battery electric vehicles (BEVs) and/or fuel cell electric vehicles (FCVEs) serving as sustainable transportation and energy storage solutions. FCEVs are here considered to be equipped with unitized reversible fuel cells, where a single stack can both provide and absorb power, acting as a fuel cell when power is required and electrolyzer when power must be absorbed, enhancing their versatility within the microgrid framework. Therefore, the present paper examines an islanded microgrid setup integrating BEVs and FCEVs and explores the potential of vehicle-to-grid (V2G) technology for frequency regulation. Through simulations conducted in MATLAB/Simulink, varying scenarios are explored by adjusting the number of BEVs/FCEVs connected to the system. Findings suggest that this solution can significantly enhance frequency regulation thanks to the rapid response these systems can provide to renewable energy fluctuations. However, the optimal integration of BEVs/FCEVs must be carefully determined to maximize system benefits.