For fuel economy of power system, Plug-in Hybrid Electric Vehicle (PHEV) should be charged late at night to level a load curve. This paper proposes an electricity pricing algorithm for load leveling, using variation method. Variation method is a mathematical technique that can bring a value of integral functional to the extreme value. We formulate a cost minimization problem of PHEV owners, regarding the integral functional as an electric bill. By solving the problem, we get the electricity price curve that can realize the ideal bottom charge while PHEV owners minimize their electric bill. We analyze the difference in results between the proposal and the target case, where PHEVs are ideally charged to raise bottom demand. The ratio of the reduction of the proposal case to the target case resulted in 99.8%. It is verified that the proposed algorithm is effective in bottom-up of daily load curve.