A fundamental study on operational strategy for a vehicle-to-grid (V2G) enabled plug-in electric vehicle (PEV) is proposed. Firstly, a cost function for the house electricity bill is constructed reflecting the reward of surplus electricity from a photovoltaic generation under feed-in-tariff and multi-step electricity pricing. In addition, a revenue function for frequency regulation is considered as well to enhance the profitability of the PEV owner. The basic structure of V2G frequency regulation is borrowed from the authors' previous work, but is revised to consider active discharging of the battery in a continuous manner. The two objective functions are then unified to yield the total electricity bill of the house. Finally, the proposed method is verified through simulations and the results are analyzed from practical point of view.