Many alternative fuel vehicle technologies, including plug-in hybrid electric vehicles (PHEVs), are currently being developed. Among the key reasons for their development is the increasing demand for fuel, which has resulted in increased fuel costs and brought attention to resource limitations. Fuel is also directly related to emissions and there is a conscious effort to minimize the environmental impact of vehicles. When evaluating the operational success of these technologies, it is important to consider the energy cycle of the vehicle. Source-to-wheel (STW) efficiency and emissions analysis is proposed in this paper to provide a value for comparing current and proposed vehicle technologies. The STW cycle includes the raw material production stage, transportation and storage stages of energy sources, energy transportation/storage/distribution stage, and finally the vehicle operations stage. The STW calculation is divided into two sections for ease of analysis. They are the cycle from the source of the energy to the vehicle and the cycle from when the energy is delivered to the vehicle to the work done at the wheels. They are referred to as the source-to-vehicle (STV) and vehicle-to-wheel (VTW) cycles, respectively. The impact of the vehicle manufacturing stage on this analysis will be addressed and the different approaches to integrating PHEVs into the current fleet of vehicles will also be discussed.