This paper presents investigations into various aspects of how plug-in hybrid electric vehicles (PHEVs) could impact the electric power system. The investigation is focused on impacts on the power system infrastructure and impacts on the primary fuel utilizations due to PHEV charging. The investigation is presented in terms of examples of typical systems. Methodologies are presented for computing loss of life of distribution transformers, which sets the basis for needed expansion or upgrades of systems with PHEV penetration. In addition, a methodology is presented for evaluating the impact on primary fuel source utilization considering all the operating constraints of an electric power system. Examples of fuel utilization impact are presented for various levels of PHEV penetration. In general, PHEVs cause a shift of fuel utilization from petroleum to less expensive fuels utilized by electric power utilities.