The concerns regarding the future of our planet are incessantly increasing, among which the environmental issue related to the impact of automotive engineering has been discussed more than ever lately. Studies show that the particulate materials and exhaust gases emitted by vehicles put them among the major polluters. Although several attempts have been made and backed by major private enterprises and government departments throughout the world on the development of hybrid electric vehicles, none has ever made it to series production. Hybrid electric vehicles are a very promising solution since they combine the qualities of both the internal combustion engine and the electric motor. Therefore, with a considerable decrease in fuel consumption and its consequent lower emission rate, the hybrid powertrain grants the vehicle a good performance as well as an acceptable driving autonomy. This paper aims at making a comparison on one of the longitudinal performance parameters, the acceleration time, for conventional and hybrid electric vehicles. The Holmes's Method is going to be used as a tool for the proposed simulation. The method consists of a graphical analysis on the available torque generated, which predicts the increment of time required for an increment in the engine rotation speed. This paper concludes that hybrid vehicles enjoy an advantage over the conventional ones regarding the acceleration time due to extra power generated by the addition of an electric branch to the powertrain.