NEMA 14-50 outlet or hardwired charger?

A NEMA 14-50 is a 240-volt, 50-amp receptacle. Under the 80 percent rule a charger plugged into one may draw at most 40 amps, about 9.6 kW, or roughly 28.2 miles an hour.

A hardwired charger is wired straight to its circuit with no plug. On a 60-amp circuit it can draw 48 amps, 11.52 kW, about 33.8 miles an hour, if the car's onboard charger can take it.

Range figures assume a car that uses 30 kWh per 100 miles and loses 12 percent of the energy between the wall and the battery. Your car's figure is on its fueleconomy.gov label; the calculator takes yours.

Reasons to choose the plug

• You might take the charger with you when you move.
• You want to swap chargers later without an electrician.
• You already have a 14-50 for an RV or a range.

Reasons to hardwire

• You want more than 40 amps and your car can use it.
• No receptacle to wear out. A receptacle that is plugged and unplugged, or that carries a heavy load for hours every night, is the weak point of a plug-in install; use an industrial-grade receptacle if you go that way.
• Outdoors, a hardwired unit avoids an exposed plug.
• Ground-fault rules. Recent editions of the National Electrical Code require ground-fault protection on receptacles that serve EV charging, and some chargers have their own. Ask your electrician which edition your town enforces and how they handle it; a hardwired install often keeps this simpler.

Either way the circuit is the same 240-volt circuit sized by the breaker rule.