The automotive industry has been driven to develop more sustainable transportation solutions, in lieu of recent legislations regarding emissions reduction. The need comes from the fact that road transport is a major contributor to greenhouse gas and other emissions. Hybrid electric vehicles proved to have significant potential to increase fuel consumption efficiency and reduce tailpipe emissions. This comes at the expense of complex Powertrain architectures, control strategies and software development, for the purpose of developing control units of the vehicle. The aim of this thesis is to implement and evaluate the performance of on-line implementable energy management system for hybrid electric vehicles.