Charging an electric car's battery is a lot different than pumping gas. How long it takes to charge depends on a number of factors, including battery size and type, but it definitely takes longer than filling a gas car's tank.
How Long It Takes to Charge an EV
Electric cars are becoming gaining popularity, but many people still want to know how long it actually takes to charge one in the real world before they actually switch over from gas. It's a fair question and one that requires a different perspective on refueling than the one we're used to from years of driving gasoline vehicles.
The main factors that influence EV charging time are:
- The maximum charge rate of your power source
- The maximum charge rate of your EV
- Battery size
- Battery status at the time of charge
- Weather
We'll go through each of them in turn.
Maximum Charge Rate
Two maximum charge rates are important when plugging an EV in for a power-up: that of your power source, and that of the vehicle itself. For the fastest possible charging, these two have to be in sync. If a charging station has a high max rate, that won't matter if the EV's max charge rate is lower, because an EV defaults to its own max rate.
An EV with a max charge rate of 7 kilowatts (kW), for example, won't charge any faster than that on an 11kW charging station --- it'll still default to 7kW. Conversely, if you plug a vehicle with an 11kW limit into a 7kW charging station, you'll only get a 7kW charge.
Depending on which level of charging station you use, an EV battery can take anywhere from days to half an hour to charge. That's because different levels of charging deliver power to the battery at different rates.
Level 1 charging, for example, is a 120-volt wall plug. It's the same kind of outlet you'd plug a kitchen appliance into. That's more accessible than home-based level 2 charging systems, but only delivers a trickle of power --- Car and Driver compares charging an EV on a level 1 output to filling a multi-gallon barrel with a squirt gun. You'll get there eventually, but it takes a long time. Charging an EV battery from almost depleted to full on a level 1 output takes days.
Level 2 chargers are 240 volts and can top up an electric car's battery in a matter of hours. The wall outlets for more heavy-duty appliances, like an electric dryer, can deliver this much power. You can also have a dedicated level 2 charging station installed, but that can get expensive. An overnight charge of around eight hours is usually enough time to regain most of an EV's power on a level 2 connection.
Level 3 rapid charging stations, also called DC fast charging or DCFC stations, are the quickest to juice up an EV. The fastest ones will get you to around 80% capacity in about half an hour, and even the slower DCFC stations will charge up in about an hour. Regular DCFC stations deliver between 43-50kW of power, Tesla's Supercharger stations can pump out up to 150kW, and the fastest rapid charging stations as of this writing can put out a whopping 350kW. Keep in mind that not all EVs can use the very fastest DCFC stations --- they may not have the proper plug or the necessary max charge rate to take advantage of them.
Battery Status and Size
How much power an electric car's battery has when plugged in to charge also affects charge time. A battery at 45% charge will take less time to top off than one at 20%, the same as any other rechargeable electronic device. It's a good idea to keep an EV's battery between 20-80% of capacity to prolong its life and peak operating condition. To keep the battery in that range and cut down charge time, many EV drivers plug in throughout the day while they're at work, getting lunch, or anywhere else they'll be for a while that has access to a charging station. This keeps the battery "topped up," and is known as top-up charging.
A battery's level of charge is sometimes referred to as "battery status" or "state of charge (SoC)." If the SoC of your battery is below 20% or above 80%, most EVs are programmed to slow down the rate of charge to protect the battery. So even if you're connected to a DCFC station, you're not getting the maximum speed if your battery is outside that optimal charge range.
The size of an electric car's battery pack, measured in kilowatt-hours (kWh) is important to consider. The battery size affects how much power it can hold, which determines the car's range. A car with a nearly depleted 100kWh battery pack, for example, would take about ten hours to charge at a 10kW charging station. A 50kWh battery would take half that time using the same power source because its capacity is smaller. Put another way, it's much easier to fill a cup with water than it is to fill a pool using the same garden hose.
Weather
Extreme weather will affect charging time and charge capacity for electric cars. Extreme cold, in particular, can cause the liquid element in a lithium-ion battery to become viscous and slow the chemical reactions necessary to produce electricity. That also makes it take longer to get a full charge. Many EVs come with a battery heating and cooling system to help mitigate the effects of inclement weather on charging time, and it's recommended that people use these systems to precondition the battery before connecting to a charging station.
No Flat Metric Yet
As of this writing, there's no one-size-fits-all metric used to measure the charge time of electric vehicles. The number of variables involved, from battery capacity to a vehicle's max charge rate, means the answer won't be the same for every EV.
Improvements in battery tech in the coming years will also change how fast and how often electric car batteries should be charged. Some manufacturers provide charging time estimates, but most of the time it will come down to doing the math based on your vehicle's max charge capacity, battery capacity, and the charging stations available in your area.