. . . Gasoline displacement from plug-in vehicles is about 42% more than it was in 2017 and about twice as much as it was in 2016.
The gasoline displacement from EV versus PHEV was split almost evenly in 2012 and 2013 but EV accounted for two-thirds of the gasoline displacement by 2018.
Direct link to Report abstract and download site: https://www.osti.gov/biblio/1506474-assessment-light-duty-plug-electric-vehicles-united-states
I recommend reading Engineer-Poet's comment at GCC.