Price parity between electric and combustion vehicles has launched electric-vehicle sales into the stratosphere in the few markets that have reached that elusive milestone. The logic is simple: Electric cars may be cleaner, cheaper to refuel and punchier from a stop than gas vehicles, but none of that carries much weight for a buyer who can't afford one in the first place.

Show consumers that EVs cost the same or less up front, though, and mass adoption can really take off.

Oddly enough, that critical turning point happened this summer in the U.S. during a time of massive uncertainty for the country’s clean-car industry. But don’t expect the trend to last.