Despite the recent commercial success of HEVs, their market share is still insufficient to produce a significant impact on energy consumption on a global basis. Moreover, it is unlikely that, in next few years, the scenario will drastically change, since relevant investments on production plants would be needed and the market does not seem to provide the expected growth for such technologies. Therefore, the possibility of upgrading conventional vehicles to hybrid electric vehicles is gaining interest. Among the diverse options for hybridization, researchers are focusing on electrification of rear wheels in front-driven vehicles, by adopting in-wheel motors and adding a lithium-ion battery. Thus, the vehicle is transformed in a Through-The-Road parallel hybrid electric vehicle.This paper presents an energy-based model, developed in Matlab/Simulink environment, of a conventional vehicle hybridized by means of such conversion kit. The model has a modular approach, where different powertrain configurations are considered, specifically with different battery sizes, different in-wheel motors power, with/without plug-in capabilities. An additional level of complexity comes from the opportunity to integrate flexible PV panels into the hybridization kit.In order to assess the benefits of the proposed kit with respect to the conventional vehicle, the analysis was performed over a variety of realistic driving cycles to reflect common driving habits. Results show that driver habits (in terms of driving style and distance driven), and the availability of charging infrastructure play an important role in fuel economy of the vehicle, thus making one configuration more convenient than others.