This paper proposes a novel charging method for plug-in hybrid electric vehicles (PHEVs) in a smart grid. It is based on a distributed and autonomous framework where users or PHEVs can adapt their charging rates according to their preferences. In particular, we borrow the concept of congestion pricing in Internet traffic control and show that pricing information is very useful to regulate user demand and hence balance network load. User preference is modeled as a willingness to pay parameter which will impact the price and charging rate. Simulation results are presented to demonstrate the dynamic behavior of the algorithm and impact of different parameters on system performance.