In recent years, the usage of various alternative energies is considered from a viewpoint of CO2 emission reduction. Toyota Motor Corporation considers that Plug-in Hybrid Electric Vehicles (PHEVs) is the best practical solution, and has launched Prius Plug-in Hybrid in January 2012. Prior to this, in December 2009, Toyota sold 650 PHEVs through lease programs for validation testing in Europe, the U.S. and Japan. As a result, not only the fuel reduction effect in case of real market usage was confirmed, but also the relationship between frequency of charging and fuel reduction effect. This paper discusses the analysis of the validation test results.