Holistic energy management of plug-in hybrid electric vehicles (PHEVs) in smart grid environment constitutes an enormous control challenge. This paper responds to this challenge by investigating the interactions among three important control tasks, i.e., charging, on-road power management, and battery degradation mitigation, in PHEVs. Three notable original contributions distinguish our work from existing endeavors. First, a new convex programming (CP)-based cost-optimal control framework is constructed to minimize the daily operational expense of a PHEV, which seamlessly integrates costs of the three tasks. Second, a straightforward but useful sensitivity assessment of the optimization outcome is executed with respect to price changes of battery and energy carriers. The potential impact of vehicle-to-grid (V2G) power flow on the PHEV economy is eventually analyzed through a multitude of comparative studies. •Integrated cost-optimal control scheme is devised to maximize PHEVs economy.•Charging, power management, and battery aging are optimally coordinated.•PHEVs evolve toward EV with future gasoline and battery prices.•Vehicle-to-grid (V2G ) implication to PHEVs economy is studied.•Convex programming powerfully optimizes plug-in hybrid drivelines.