All-electric vehicle (EV) and plug-in hybrid vehicle (PHEV) sales in the United States have generally increased since their introduction in 2010, and the sales of both vehicle types remained fairly close until 2018. Since May 2018, EV sales have exceeded the sales of PHEVs every month, sometimes by wide margins. In December 2018, EV sales reached 36,961—about three times higher than PHEV sales for that month, and more than 7,000 higher than conventional hybrid electric vehicles (HEV), which have been on the market for about two decades.
Source: Argonne National Laboratory, Light-Duty Electric Drive Vehicles Monthly Sales Update Program, August 2019.