In this paper, we consider smart charging systems for plug-in electric vehicles. We formulate an optimization problem of smart charging scheduling in which the charging schedule is optimized so that it supplies sufficient electricity for the next trip and also minimizes the charging cost under given time-of-use (TOU) rate structures while it follows demand response (DR) events requested by a utility, and we also present an algorithm to solve the optimization problem. To validate the effectiveness of our smart charging system, we first developed and implemented a smart charging system using SEP 2.0 and SAE J2836/2847/J2931 and conducted demonstration experiments in which a total of 10 customers of Duke Energy regularly used our developed system for approximately one year with simulated TOU rate structures and DR events. We also present the results of the experiments for our developed smart charging system to show the cost benefits for users without forcing their patience and the impact on peak demand shift by the user-friendly system.