The rate at which plug-in electric vehicles (PEV) enter the U.S. vehicle stock depends on many factors, including battery cost and reliability, the price of gasoline, and government incentive programs. Plausible scenarios of PEV population in the year 2030 range from a conservative 3.3 million to an aggressive 100 million, as shown in the figure below. Most of these scenarios are specifically for plug-in hybrid electric vehicles (PHEVs), i.e., plug-ins having internal combustion engines. Until recently, most projections assumed that PHEVs would be the dominant plug-in technology for many years to come. With an all-electric vehicle (EV) arriving in the U.S. later this year and renewed optimism for this technology, some manufacturers see EVs taking over before 2030.