Plug-in hybrid electric vehicles (PHEVs) are a transportation technology on the cusp of introduction that has the potential to couple the transportation and electricity energy systems. A multiparadigm model of the electricity and transportation systems of Alexandria, Virginia has been developed in order to examine the effects of PHEV introduction. This model combines detailed subsector models of the transportation, household electricity demand, and electricity supply sectors. The effects of PHEV adoption on the electricity supply sector have been explored through an examination of the changes in both total electricity usage and peak electricity demand that could be expected. Additionally, the differences in emissions of carbon dioxide, nitrous oxides, and sulfur dioxide between conventional vehicles and PHEVs charged under varying electricity supply mixtures has been quantified. The results indicate that the charging pattern of the vehicles used can significantly alter the effects on the system as a whole.