while DC fast-charging garners all the headlines and much of the funding, the overwhelming majority of EV charging is AC charging, usually at home—80 percent of it, in fact. People who own and live in a single family home are overrepresented among EV owners, and data from the National Renewable Energy Laboratory from a few years ago found that 42 percent of homeowners park near an electrical outlet capable of level 2 (240 V) AC charging.

"90 percent of all houses can add a 240 V outlet near where cars could be parked," said Abuelsamid. "Parking behavior, namely whether homeowners use a private garage for parking or storage, will likely become a key factor in EV adoption. Today, garage-use intent is potentially a greater factor for in-house charging ability than the house’s capacity to add 240 V outlets."

Just because 90 percent of houses could add a 240 V outlet near where they park, it doesn't mean that 90 percent of homes have a 240 V outlet near where they park. According to that same NREL study, almost 34 million of those homes will require extensive electrical work to upgrade their wiring and panels to cope with the added demands of a level 2 charger (at least 30 A), and that can cost thousands and thousands of dollars.

Twenty-three percent of Americans live in multifamily dwellings, including apartments, condos, and townhomes. Here, the barriers to charging where you park are much greater. Individual drivers will rarely be able to decide for themselves to add a charger—the management company, landlord, co-op board, or whoever else is in charge of the development has to grant permission.