Recent years have seen the flourishing of the so called green wave and environment-related topics have been discussed in many ways for various reasons. The use of Hybrid Electric Vehicles (HEVs) is a valid way to achieve tank-to-wheel (TTW) CO2 emissions reduction. The choice of the design parameters, such as engine displacement or power of the electric machine, remains of fundamental importance. To this end, various algorithms have been deployed to effectively calculate the TTW CO2 emissions of a specific HEV layout. One of this is Dynamic Programming (DP). However, it cannot always be used as it requires high computational power and time.