In the last decade, Hybrid Electric Vehicles have spread worldwide in passenger cars applications, for their capability to decrease fuel consumption and emissions. However, in the Medium and Heavy Duty market this technology is not as common, while it could represent a valid solution to increase the overall efficiency of these vehicles. Since Heavy Duty vehicles’ lifespan is typically above one million kilometers, and their fuel consumption is much greater than passenger cars’ vehicles, mainly because of their considerable mass and their higher aerodynamic coefficient, it is clear how even a slight increase in efficiency could represent a substantial economic advantage throughout the life cycle of the vehicle.