Recently even for medium or heavy duty commercial vehicles (MD/HD CVs), hybrid electric vehicles (HEVs) or electric vehicles (EVs) have been launching in the world. In the current status, parallel type of HEV shows the most practicality in market. In that case, the optimal engine adaptation and the highly efficient brake energy recovery are the keys for efficient HEV. The EV application for MD/HD CVs is also the possible solution in the near future if some issues are cleared. Therefore it is hard to decide the most possible case for future CVs only from the existing point of view. The conceptual new name of “XEV” will be suitable to express those possible cases generically. The improvement of energy storage system (ESS) will have been the most prioritized issue for “XEV” for a while.