How Long Does It Take to Charge an EV? One Formula and Three Ceilings

Charging time is one division: battery kilowatt-hours divided by charging kilowatts, then about ten percent longer for the loss in converting AC to DC. A 75 kWh battery on a 9.6 kW home charger fills in roughly 8.7 hours. Everything else is which number goes in the denominator.

Most answers to this question give a range so wide it is useless — “four to forty hours” — because they average over three different kinds of charging. Splitting them apart makes the arithmetic simple again.

The formula, and where the ten percent goes

Power in kilowatts is volts times amps, divided by a thousand. Forty amps at 240 V is 9.6 kW. Twelve amps at 120 V is 1.44 kW. That is the number your charger delivers.

Not all of it reaches the battery. The car’s onboard charger converts AC to DC and loses some of it as heat, and the battery loses a little more. Around ninety percent arriving at the pack is a reasonable working figure for Level 2 charging, so the honest formula is:

hours = battery kWh ÷ (charging kW × 0.9)

Empty to full, by power level

Battery	1.44 kW (120 V, 12 A)	3.84 kW (240 V, 16 A)	7.68 kW (240 V, 32 A)	9.60 kW (240 V, 40 A)
50 kWh	38.6 h	14.5 h	7.2 h	5.8 h
60 kWh	46.3 h	17.4 h	8.7 h	6.9 h
75 kWh	57.9 h	21.7 h	10.9 h	8.7 h
90 kWh	69.4 h	26.0 h	13.0 h	10.4 h
100 kWh	77.2 h	28.9 h	14.5 h	11.6 h

Twenty to eighty percent, which is what people actually do

Nobody runs an EV to zero and then fills it. The everyday cycle is a partial top-up, and 60 percent of the pack is a realistic slice.

Battery	1.44 kW	3.84 kW	7.68 kW	9.60 kW
50 kWh	23.1 h	8.7 h	4.3 h	3.5 h
60 kWh	27.8 h	10.4 h	5.2 h	4.2 h
75 kWh	34.7 h	13.0 h	6.5 h	5.2 h
90 kWh	41.7 h	15.6 h	7.8 h	6.2 h
100 kWh	46.3 h	17.4 h	8.7 h	6.9 h

At 9.6 kW every pack size in that table finishes inside a single night. At 1.44 kW none of them does, which is the whole case for a 240 V circuit.

Range added per hour, which is the number that matters overnight

Hours-to-full is the wrong frame for a car that sleeps at home. The right one is how much range appears while it is plugged in.

Charger draw	Range added per hour	8 hours plugged in	12 hours plugged in
1.44 kW	3 to 5 miles	26 to 40 miles	40 to 60 miles
3.84 kW	9 to 13 miles	71 to 108 miles	106 to 161 miles
7.68 kW	18 to 27 miles	141 to 215 miles	212 to 323 miles
9.60 kW	22 to 34 miles	177 to 269 miles	265 to 403 miles

These figures use 2.3 to 3.5 miles per kilowatt-hour, and there is a reason to trust that band rather than take it on faith: it is the band that reproduces INFGO’s own published figures of 9 to 13 miles per hour at 3.84 kW and 3 to 5 at 1.44 kW, both of which appear in the table above. Because those published figures are measured per hour of charging at the plug, the band already absorbs the conversion loss. Do not apply the ten percent twice.

The practical reading of that table: at 9.6 kW an eight-hour night covers more than a week of average American driving. Most households do not need a faster charger. They need a 240 V circuit.

The three ceilings

Charging speed is the lowest of three limits, and the one people forget is the third.

The circuit. A continuous load is rated at 125 percent of the draw, so a 50 A breaker supports 40 A and 9.6 kW; a 30 A breaker supports 24 A and 5.76 kW. This is not a rule of thumb: the 125 percent rule applied to 40 A gives the 50 A breaker and 8 AWG cable INFGO specifies for its own 40 A charger. Which 50 A outlet to install is a separate question, answered in NEMA 14-50 vs 6-50.

The charger. Its maximum, and on an adjustable unit whatever setting you left it on. INFGO’s 40 A models step through 8, 12, 16, 20, 24, 32 and 40 A, which exists so a charger can match a smaller circuit rather than trip it.

The car’s onboard charger. This is the ceiling that surprises people. Every EV converts AC to DC on board, and that converter has its own rating.

The car’s AC limit	Amps at 240 V	Range added per hour	What a 9.6 kW charger gives it
3.6 kW	15 A	8 to 13 miles	3.6 kW
6.6 kW	27.5 A	15 to 23 miles	6.6 kW
7.7 kW	32 A	18 to 27 miles	7.7 kW
9.6 kW	40 A	22 to 34 miles	9.6 kW
11.5 kW	48 A	26 to 40 miles	9.6 kW

A car capped at 7.7 kW charges at 7.7 kW from a 9.6 kW charger, an 11 kW charger and a 19 kW charger alike. Before paying for more amps, check the car’s stated maximum AC charging rate. It is the cheapest specification to look up and the one most often skipped.

DC fast charging is a different mechanism

Level 1 and Level 2 send AC to the car and let the car convert it. DC fast charging bypasses the onboard charger entirely and feeds the battery directly, which is why it is measured in tens of minutes rather than hours.

Battery	10 to 80 percent	At 50 kW	At 150 kW	At 250 kW
60 kWh	42 kWh	50 min	17 min	10 min
75 kWh	52 kWh	63 min	21 min	13 min
100 kWh	70 kWh	84 min	28 min	17 min

Treat those as floors, not forecasts. DC power tapers as the battery fills — steeply above about 80 percent, which is why the 10-to-80 window is the one everyone quotes — and the station, the cable and the car each impose their own limit. A NACS-to-CCS adapter opens Tesla V3 and V4 Superchargers to a CCS1 car — why V1 and V2 stay closed is a protocol story, not a connector one — and there the station’s peak and the car’s acceptance rate decide between them which of those columns you get.

Putting it together

For a household with a car that sleeps at home, the sequence is: find the car’s AC limit, find the biggest circuit you can reasonably run, and buy a charger that covers both. That usually lands on 40 A and a 50 A circuit, which is INFGO’s 40 A Level 2 charger in J1772 or the NACS version for a Tesla.

If a 240 V circuit is genuinely out of reach, a portable Level 1 and 2 charger covers both cases: 1.44 kW from an ordinary outlet, 3.84 kW when you find a 240 V one. Three to five miles an hour is not a charge, but over a weekend it is a hundred miles, and it fits in the boot.

Have any new circuit installed by a licensed electrician to your local code. The arithmetic on this page sizes the equipment; it does not size the wire.