Yahoo Autos How Long Does it Take to Charge an Electric Car?
It is a common assumption that it takes more time for an EV to charge than for a conventional vehicle to refuel at a pump. This isn’t an unreasonable assumption. After all, electric cars can take between 30 minutes and a week to charge, depending on a variety of factors. How could anyone fit so much charge time into their everyday life?
But many new EV adopters will spend less time waiting for their vehicle to charge than they are used to spending at the pump, though the time might be concentrated into fewer, longer visits per year. Unlike gas pumps, chargers allow owners to set up a session and walk away. For an average U.S. driver, charging overnight at even the slowest charger will provide more than enough juice to get through the next day.
As illustrated here, this all can be easily calculated based on the length of daily travel, vehicle efficiency, and charger operation. The obvious stuff.
Level 1 Charging
Level 1 charging is plugging a car directly into a standard 120V wall outlet. All EVs come with the required cables, so assuming one has electrical service (according to the World Bank, that’s 100 percent of the United States population), there’s no additional upfront cost. The maximum power obtainable from an outlet is the voltage multiplied by the maximum electrical current, measured in amps, that won’t trip the circuit breaker: P(power) = I(current) * V(voltage).
In the U.S., the most common amperage allowed on a 120V circuit is 15 amps, which translates to 1800 watts or 1.8 kW of power. To leave a bit of extra safety margin, companies generally cap consumer devices around 1500 watts (1.5 kW), which is a typical rating for any significant heating devices like space heaters, kettles, and hair dryers.
The math for how long a car takes to charge is simple at low rates like this. It’s the energy capacity of the EV’s battery in kWh divided by the power the charger delivers in kW. Assuming a capacity of 75 kWh, the time to charge from completely empty to totally full can be calculated as follows:
75 kWh / 1.5 kW = 50 hours = ~2 days
Two days is too long, but given the limited miles most people drive daily, access to overnight charging allows average drivers to keep their vehicles sufficiently charged using a Level 1 charger. “Most people” obviously aren’t all people. And Level 1 charging is best used by EV owners with consistent and predictable driving patterns within the parameters of the vehicle’s range and performance.
For example, assume a 40-mile round-trip daily commute, leaving the house at 8 a.m. and arriving home around 7 p.m. With a reasonably efficient car like a Tesla Model 3 or Lucid Air, expect to consume energy at a rate of around 250 Wh/mile. Plugging in after arriving back home would require about seven hours to charge fully.
Bottom line on L1 charging: A Level 1 charger can provide up to roughly twice the energy required to cover the average commute in the U.S. But it won’t be possible for everyone to rely on such a slow charger.
Level 2 Charging
Level 2 charging is similar to Level 1, but instead of connecting to a 120V circuit, the EV connects to a 208-240V circuit that supports a higher current and delivers more power. Beyond that, how much power an EV can use varies. All EVs have an onboard charger, where the required conversion from AC to DC happens for L1 and L2 charging, and the maximum power that this charger can deliver to the battery ranges by car.
The Amperage of 240V Circuits
Homes are generally wired to support at least a few 240V devices, like clothes dryers, ovens, cooktops, and water heaters, which require more than 1.5 kW. Again, because P(power) = I(current) * V(voltage), how much power can be drawn from an outlet on one 240V circuit depends on how many amps of current that circuit is configured to support. Typically, these circuits are between 20 and 100 amps. Meanwhile, a wall-mounted L2 charger—which is really a glorified extension cord— is typically rated between 16 and 80 amps, including a safety margin. This means the range of power that could be delivered from your outlet to your EV is between 3.8 and 19.2 kW.
The Onboard Charger
That’s not the end of the analysis for determining charging speed because once the power level gets that high, there is a second choke-point besides the circuit breaker and charging cord, and it’s inside the car. With both L1 and L2 charging, what enables plugging into a regular outlet is the conversion from AC to DC that happens inside the car. As mentioned above, every EV has an onboard charger with a maximum amount of power it can deliver to the battery.
Generally, the larger the battery on the car, the larger the onboard charger will be. A Tesla Model 3 and Hyundai Ioniq 5 have an 11-kW onboard charger, while the GMC Hummer EV and Ford’s F150 Lightning have 19.2-kW units. With smaller EVs, there is no additional benefit to installing a 80-amp charger versus a 48-amp in a home, as the car will be limited by its onboard charger.
So, calculating how long it takes to charge fully using L2 charging is different from L1, depending on the onboard charger. First, calculate the power delivered by the circuit, which is 240V multiplied by the circuit’s amp rating minus a 20% safety margin (ie 30A becomes 24A).
240V * 24A = 5.8kW
The power delivered to the car is whatever is smaller between the circuit power and the power of the car’s onboard charger. Then, divide the battery capacity by the power delivered to the car. For an Ioniq 5 with a 77kWh battery and a 11kW onboard charger, the math for various charging options is as follows:
77 kWh / 5.8 kW (24A) = 13 hours
77 kWh / 7.7 kW (32A) = 10 hours
77 kWh / 9.6 kW (40A) = 8 hours
77 kWh / 11 kW (48A or 80A) = 7 hours
On the flip side, more powerful chargers may be necessary to charge a larger, more heavily used vehicle overnight fully. The Ford F150 Lightning has a 131-kWh battery and a 19.2-kW onboard charger that doesn’t max out on a 48A-amp charger, so the full charge times for it are as follows:
131 kWh / 5.8 kW (24A) = 23 hours
131 kWh / 7.7 kW (32A) = 17 hours
131 kWh / 9.6 kW (40A) = 14 hours
131 kWh / 11 kW (48A) = 12 hours
131 kWh / 19.2 kW (80A) = 6.8 hours
Finally, some new examples of extremely large EVs really push the limits of what L2 charging infrastructure can handle in a reasonable amount of time. The Cadillac Escalade IQ has a 200-kWh battery, the GMC Hummer EV boasts 212 kWh, and the upcoming Dodge Ram REV holds up to a staggering 229-kWh battery. Let’s do the same math for the Dodge.
