Energy management of vehicles is an important issue to meet the targets of CO2-emission regulations of vehicles. The variety of recently introduced vehicle concepts including HEVs and EVs imply a remarkable optimisation potential. Therefore a simulation method was developed which allows the consideration of multiple vehicle topologies with respect to driving performance, vehicle dynamics and energy management. Different user-related and legal-based driving cycles for both passenger cars and commercial trucks were analysed to verify energy flows and CO2 emissions. The energy saving potential of waste heat recovery using thermoelectric generators is presented as an example application.