The charging time of an electric car depends on a number of factors, including the size of the car’s battery, the speed of the charging station, the maximum capacity of the car’s onboard charger, how much charge the battery has when plugging in, and the ambient temperature. We discuss these factors in detail in the following analysis.
How does battery size affect charging?
All else being equal, a larger battery will take longer to charge than a smaller battery, which is not surprising. EV battery sizes today range from about 30 kWh to more than 200 kWh. Note that these are gross figures; the net usable capacity is always somewhat less because it’s not good for the battery to be completely charged or discharged. To illustrate the impact of battery size on charging time, consider two EVs, one with a usable battery capacity of 40 kWh and the other with a usable capacity of 80 kWh. If you’re charging at a Level 2 charger (more on which below) running at 15 kW, that means your battery will recharge at a rate of 15 kW per hour. We’re oversimplifying a bit, but if you do the math, the smaller battery will recharge from empty to full in less than three hours, while the larger one will need more than five hours.
What are the different charging station speeds?
This is the EV equivalent of gas-pump speed, and there are effectively three speeds to be aware of, in order from slow to fast: Level 1, Level 2, and DC fast charging or Level 3. We’ll explain each one in turn.
Level 1 charging
If you’re using the standard outlet in your home, it is rated at 120 volts, which is known in the world of EV charging as Level 1. It’s the most convenient level, of course, since just about everyone has an outlet somewhere, but it can take seemingly forever. For example, a 2023 Chevrolet Bolt EV using a standard 120-volt outlet will charge at a rate of 4 miles of range per hour, meaning it would take about 65 hours to get to a full charge from empty. On the extreme end, a 2023 GMC Hummer EV, which has a huge battery, could take up to 200 hours for a full charge using the same outlet.
Level 1 charging is best suited for plug-in hybrids such as the Toyota Prius Prime, which would be fully charged in about five and a half hours. You could theoretically get by on Level 1 charging with a smaller EV like the Nissan Leaf or the Mini Cooper Electric provided you don’t drive much and can plug in every night.
Level 2 charging
Level 2 charging uses a 240-volt outlet and represents the fastest way to charge at home, as anything greater can only be found in industrial or commercial settings. While there are multiple 240-volt outlet types, only a couple are suitable for EV charging (either a NEMA 6-50 or a NEMA 14-50). You’ll likely need an electrician to verify if you have the proper outlet in your home and to check if your home can accommodate the extra draw in power. The same Chevy Bolt we referenced earlier would take approximately seven hours to charge to full on a Level 2 charger. The Prius Prime, which has a much smaller battery, would charge in about two hours. The Hummer EV, though, would still need about 20 hours to go from zero to a full charge.
DC fast charging (Level 3)
DC fast chargers are usually found in office parks, shopping centers or dedicated charging stations. A DC fast-charging station’s charge rate is not measured in volts but rather in kilowatts (kW). It is called DC (“direct current”) because in this method of charging, the power goes directly to the battery rather than flowing through the vehicle’s onboard charger (more on that below). Level 3 stations generally range from 25 kW on the lower end to 350 kW on the high end.
DC fast chargers can add range at a rate of about 180 to 240 miles per hour, according to the U.S. Department of Transportation. Chevrolet says that the Bolt EV can add up to 100 miles in 30 minutes on a DC fast charger. The Hummer EV, which is capable of higher charging speeds, can add roughly the same range in just 10 minutes despite its massive battery — so when you unleash the Hummer via DC charging, it’s a fast-charge champion. Just be ready for a relatively hefty bill.
Indeed, Level 3 charge stations are the most expensive and a full charge can sometimes approach the price of a tank of gas, even if you’re not driving a Hummer EV. This is due in significant part to their high installation and maintenance costs. We also should note that extended use of DC fast chargers is hard on the battery due to the higher temperatures generated, which can shorten its lifespan. It is therefore not a wise idea to use fast chargers as your primary source of charging. These stations are best used for road trips or when you need to top off for an extended day of driving.
Tesla Superchargers
Wait, aren’t there only three levels of charging speed? Yes, but Tesla’s proprietary Supercharger network merits a separate entry. Superchargers are classified as DC fast chargers, supporting a peak charge rate of up to 250 kW per vehicle. According to Tesla’s site, which assumes that the vehicles are operating at peak efficiency and the max charge rate, the Tesla Model Y can recover up to 162 miles in 15 minutes, the Tesla Model 3 and the Tesla Model X can charge up to 175 miles in 15 minutes, and the Tesla Model S is the leader with a rate of up to 200 miles in 15 minutes. In light of the White House’s announcement that the Supercharger network will be opening up to other brands, it will be interesting to see what kind of charging performance non-Tesla models can achieve at Supercharger stations.
What determines the maximum vehicle charging speed?
The charging speed limit with Level 1 and Level 2 chargers is dictated by the vehicle’s onboard charger. It’s confusing — most people think there’s only one charger and it’s the thing on the other end of the plug, but the onboard charger is actually inside the vehicle. An electric car’s onboard charger receives AC power through the charge port and converts it into DC power that the EV battery can use and store. The onboard charger is rated in kilowatts, with a bigger number offering a faster charge. The current Chevy Bolt, for example, uses an 11-kW onboard charger. Compare that to the slower 6.6-kW charger on the Nissan Leaf and you get a sense of how much of a difference this can make in EV charging time. The Porsche Taycan, one of the fastest-charging EVs, can be ordered with a 19.2-kW onboard charger.
As noted, DC fast charging bypasses the onboard charger and delivers electricity straight to the battery. This allows an electric car to receive more electrical current and charge at a faster speed. In the DC (Level 3) scenario, the charge speed is governed by the vehicle’s battery management system. This system tries to charge as fast as possible without overheating or otherwise taxing the battery. Each EV has its own maximum charging speed, which is important to know when selecting a charging station. The 2023 Chevrolet Bolt, for example, has a maximum charge rate of 55 kW, while the 2023 Mustang Mach-E has a maximum charge rate of 150 kW and most Teslas can achieve a maximum rate of 250 kW. So if you owned a Bolt EV and parked at a 150-kW charging station, the higher speed of that station would do you no good because your car is limited to 55 kW. As a courtesy, it is good to know these speeds so that other cars that need that extra speed can use it.
What are the other big factors in EV charge times?
We covered the major players above, but there are additional considerations that make EV charging even more complex. Here are two significant examples.
Temperature and weather conditions
Batteries like to be in the Goldilocks zone, not too hot and not too cold. This applies both when charging and when driving in extreme temperatures. Colder temperatures will not only lead to longer charging times, they’ll also cut down on your range. Hot temperatures, meanwhile, can lead to greater wear on the battery since the chemical reactions are happening at higher temperatures than normal. This can potentially shorten the battery’s lifespan. The higher the temperature, the more stress it places on the battery and the way its energy flows.
Using the climate control system also tends to reduce range. Using the heater has the greatest effect on range since an electric car doesn’t have an engine to generate heat like a gas car. A study by AAA concluded that on a 20-degree Farenheit day with the heater on, the driving range decreases by 41%. On a 95-degree day with the air conditioner on, AAA found that the range decreases by about 17%.
The current state of charge of the battery
Think of charging an electric car as trying to fill a glass with water from a pitcher. You’ll start out fast at first, but as the glass starts to get full, you need to slow down the stream to avoid overflowing and spilling the water. The same logic applies to charging an electric car. This means that if you arrive at a charge station with a nearly depleted battery, it will charge at a faster rate than if you showed up with the battery three-quarters full. The sweet spot for most batteries, cars or smartphones is from 20% to 80%. If you keep your electric car between those ranges, the battery will have a greater lifespan.
Since the charge needs to slow down as the battery is nearly full, going from 80% to 100% will take significantly longer. The same goes for fast chargers, as the vehicle will slow down the rate of charging the closer it gets to 100%. In some cases, it can take nearly as long (if not longer) to go from 80% to 100% as it does from 20% to 80%.
Most manufacturers recommend charging to 80% capacity for daily driving and only going to 100% when you need to take a longer road trip. This will not only take care of the battery but also reduce the time spent charging.
Edmunds says
All the factors that influence electric car charge speeds might seem overwhelming, but think of it this way — many of these factors, including the weather, how full the tank is, and what pump you’re using, also affect gas-powered cars. Understanding how long it takes to charge an electric car is just a matter of reframing and learning a few more concepts.