DC fast charging, explained

Image source: Electrek

Most drivers have had at least one experience in which they asked themselves, “Am I going to run out of gas?” Range anxiety, or the fear a car will run out of fuel before it reaches its destination, is not unique to electric cars. It is, however, a common reason as to why drivers stick with gasoline-powered cars when electric cars are cheaper to ownbetter for the environment, and more fun to drive.

Based on the experience of EV drivers, the adjustment to charging is easier than expected and feelings of range anxiety dissipate quickly. Instead of making a detour to the gas station, drivers learn to plug in at their homes, workplaces, or parking lots. Level I and Level II charging is fast enough to meet the demands of these everyday trips. 

But still, sometimes people need to drive hundreds of miles in a day. As more people adopt EVs, DC fast charging provides an element of convenience and security that can help displace the purchase of gasoline-powered cars. But how exactly does it work, how fast is it, and how much better can we expect it to be?

How fast is fast charging?

Unlike Level I and Level II charging stations, DC fast chargers are only available for public use. You can’t install one in your home because of the extremely high voltage and power needed to reach fast charging speeds.

Photo credit: Green Car Reports

Charging speed is typically expressed in terms of power (measured in kilowatts) and varies depending on the car and the station you’re plugged into. For example, the Chevrolet Bolt can charge at a peak of 50 kW, while competitors like the Hyundai Kona EV or Kia Niro EV can charge at a maximum of 77 kW. You can convert these specs into charging times using the chart below.

Station outputCharging rate
25 kW50 miles in 30 minutes
50 kW90 miles in 30 minutes
100 kW120 miles in 30 minutes
150 kW150 miles in 30 minutes
Although different car models have different maximum charging rates, the actual charging rate depends on the power of the station you plug into.

Many of the DC fast charging stations available now charge at rates of 24 to 50 kW, but these speeds are becoming obsolete as electric car models are introduced with faster charging capabilities. In an effort to keep infrastructure ahead of vehicle technology, companies like Electrify America and EVGo are building networks of stations to charge at rates of 150 kW or more, even though few vehicles can charge at these rates currently.

It’s a formula that Tesla has mastered early with its proprietary network of Superchargers, which are known for widespread station abundance and power. Tesla Superchargers deliver at least 120 kW, and most Tesla cars can take advantage of them because the company makes improvements to its cars through periodic software updates. The third iteration of Superchargers can output power at a rate of 250 kW, which is enough to add 75 miles of range in 5 minutes of charging or over 200 miles of range in 30 minutes.

Orange stations are fast chargers, green stations are public Level I or Level II chargers. If you’re considering buying or leasing an EV, check out the closest charger to you on PlugShare

What’s the future of DC fast charging?

Will EVs ever reach the refueling speed of gasoline? Probably. But getting 300 miles of range in 5 minutes of charging is not necessary to make electric cars practical for the majority of people. If a driver has easy-to-access options for Level I or Level II charging at home, work, or the grocery store, convenience can quell range anxiety without having to invest in as many expensive DC fast chargers.

The fact is, a 300 mile trip in a single day happens infrequently for most people. With a little extra planning and a 30-minute stop to stretch your legs and grab a coffee, DC fast charging can already enable those trips. But as more drivers go electric, we’ll need more stations.

In the short term, the installation of new DC fast charging stations should be prioritized along interstate and highly-trafficked routes to accommodate long-distance driving. Data collected from drivers can help install DC fast chargers strategically to improve access to on-the-go charging and get the most out of investment dollars in cities and rural areas. Long road trips make up a small portion of our driving miles, and most EV drivers will continue to find charging at home most convenient. 

Charging at home is the most popular charging option among EV owners. DC fast charging is a necessity for long distance trips, which make up a small fraction of driving miles. Many EV drivers have never used a single fast charging station.

In the long term, it’s possible that 200+ kW charging does become the norm, and cars may not need huge battery packs to support 400+ miles of range. The vision for Lucid, a new electric car manufacturer started by a former Tesla employee, relies on small, 30 kWh batteries, ultra-high efficiency, and widespread, 350 kW fast charging stations.

As quickly as the industry is growing, it’s unclear how long such a breakthrough would take or how expensive it would be to develop the necessary infrastructure to make this vision possible. It costs between $10,000 and $40,000 to install a single 50 kW DC fast charging port and as much as $100,000 for a 250 kW charger. They’re not going to appear on every street corner overnight.

At its simplest, DC fast charging is the best way to compete with the 5-minute refueling time of a gas-powered car. Long distance travel is a convenience that many drivers can’t sacrifice, and while there’s still plenty of room for improvement for fast charging networks, it’s doable to go electric now. Learn more at drivegreen.nationalgridus.com/learn/charging.

Electric Car Charging 101

Electric cars are a new technology, so making the transition from gas to electric can be intimidating at first. But if you can charge a smart phone, the adjustment to an electric car is easier than you might think.

Here’s a crash course to help you learn the basics of electric vehicle (EV) charging.

What kind of charging is available?

There are three levels of charging for electric cars today: Level I, Level II, and DC fast charging.

  • Level I charging requires a standard 120-volt outlet. All electric vehicles come equipped with a cord that you can plug into a common outlet. It’s exactly like charging a smartphone or laptop.
  • Level II charging requires a 240-volt outlet and a charging unit. You can purchase a Level II charging unit and install it in your home with the help of a licensed electrician, but stations are also available at public garages, grocery stores, gyms, or other public lots.
  • DC fast charging is the fastest charging available for passenger cars. You cannot install a DC fast charging unit in your home, but they are available for public use for charging on the go, mostly along highways.
Most EV drivers charge at home as a matter of convenience. However, public charging at grocery stores, shopping malls, and public parking lots makes it easier for drivers to charge on-the-go or when they need a little extra juice.

How Long Will It Take To Charge?

Charging is totally different from refilling gasoline. Most gas-powered cars are refueled when they are nearly empty, perhaps once a week. On the other hand, EVs are charged like smart phones; you plug in regularly, before you get close to 0%.

EV charging takes advantage of all the time cars spend parked, which is estimated to be 95% of the time. Even though it takes longer than pumping gas, charging is not time spent actively attending to the car – it’s time spent sleeping, eating, or working while the car is parked, so don’t be scared away by seemingly long charging times. In fact, since it takes less time to plug in at home or at work than to drive to a station and pump gas, EVs can save time that you would otherwise spend driving to and from the gas station.

The chart below shows the time it takes to go from empty to full charge of some popular EV models.

CarRangeLevel I Charging TimeLevel II Charging Time
Chevy Bolt238 miles43 hours8.5 hours
Hyundai Kona258 miles45.5 hours9 hours
Tesla Model 3, Standard240 miles36 hours6.5 hours
Kia Niro EV239 miles60 hours10 hours
Nissan LEAF151 miles28.5 hours6 hours
Nissan LEAF Plus226 miles60 hours11 hours
Toyota Prius Prime25 miles6.5 hours2.5 hours
Honda Clarity Plug-in47 miles12 hours2.5 hours
Don’t be scared away by seemingly long charge times! EV drivers often plug in to recharge the miles they’ve driven in a single day. Source: ClipperCreek

There’s a lot of variability in the charging times listed above, which makes it hard to compare different cars on an apples-to-apples basis. In general, the further a car can travel on a single charge, the bigger its battery is, and the more time it takes to charge back to 100%. To get a clearer comparison, we should be looking at charging rate, or miles of range gained per hour of charging.

The chart below shows average charging rates for the same group of EVs, though ambient temperature and the battery’s state of charge will cause small fluctuations in the actual rate. (Batteries charge faster between 20% and 80% capacity than when they’re nearly full or nearly empty.)

CarAcceptance rateLevel I Charging RateLevel II Charging Rate
Chevy Bolt7.2 kW4 miles/hour24 miles/hour
Hyundai Kona7.2 kW4 miles/hour24 miles/hour
Tesla Model 3, Standard7.7 kW4 miles/hour25 miles/hour
Kia Niro EV7.2 kW4 miles/hour24 miles/hour
Nissan LEAF6.6 kW4 miles/hour22 miles/hour
Nissan LEAF Plus6.6 kW4 miles/hour22 miles/hour
Toyota Prius Prime3.3 kW4 miles/hour11 miles/hour
Honda Clarity Plug-in3.3 kW4 miles/hour11 miles/hour
Source: ClipperCreek

The chart shows EVs all charge at the same rate when plugged into a regular outlet, no matter the battery size. When it comes to Level II charging, the two plug-in hybrids (the Toyota Prius Prime and the Honda Clarity) charge at a slower rate than battery-electrics. Otherwise, there is little difference in charging rate among the cars of the same class. Why is that?

What Happens When You Plug In

When most people say “charger,” they mean the cable that connects the power source to the device being charged, but that’s not quite accurate. An EV’s onboard charger is located inside the car and converts AC power from the wall outlet to DC power that can be stored in the battery. The speed at which an electric car can charge is limited either by the acceptance rate of the onboard charger or the power coming from the wall outlet – whichever is lower. Take a look at the diagram below to see how energy flows to the battery during charging.

onboard charger ev diagram
Electric Vehicle Supply Equipment (EVSE) is just a fancy term for charging station. For Level I and Level II charging, the onboard charger determines the fastest rate that a car can charge. In the diagram, it’s clear that all energy has to go through the onboard charger before it can be stored in the battery. Source

Level I charging delivers about 4 miles of electric range per hour of charging for all electric cars because the maximum power that a common outlet can deliver is 1.4 kW. All new EV models have acceptance rates that exceed 1.4 kW, but since the power that comes from the outlet is limited to 1.4 kW, the charging rate of the car is too.

There is more variability in Level II charging speeds because different EVs have different acceptance rates. The EVs with similar charging rates, such as the Chevy Bolt, Kia Niro, and Hyundai Kona, all have a 7.2 kW onboard charger and charge at a rate of about 24 miles per hour. The Tesla Model 3 has a 7.7 kW charger, so it adds an additional mile of driving range per hour of charging on Level II.

However, having an onboard charger with a higher acceptance rate adds weight and cost to the car. That’s why plug-in hybrids tend to have lower acceptance rates than battery-electric vehicles – around 3.3 kW compared to 7.2 kW.

Charging at home

The majority of EV drivers choose to charge at home because it’s convenient and easy. For some, a simple household outlet to gain 4 miles of range per hour of charging is enough. For others, installing a Level II charging station at home can recharge an EV battery from 0% to 100% overnight, making electric cars more convenient.

installing EVSE
Installing a charging station in your home costs around $1,200 on average, including the electrician’s time and the charging unit. 

There are EV charging stations that can deliver more or less power from the same 240-volt outlet because they draw more or less current; charging stations can deliver 12 to 80 amps, so charging rates for Level II chargers can vary between 3.8 kW and 15.4 kW.

When shopping for an at-home Level II charging station, its power output should roughly match the EV’s acceptance rate. More powerful stations are more expensive. Here are a few factors to consider when comparison shopping for your EVSE.

  • Current 32 amp chargers will suffice for most EVs. Check your car’s specs before buying a charging station. Shelling out more money for a high-current station won’t necessarily make your car charge faster. 
  • Cord length – The cord should easily reach your plug port from the station. Going with a longer cord offers you a little more flexibility; 25 feet is recommended for most people, but measure to make sure that’s enough. You cannot use an extension cord to give yourself extra length!
  • Smart features – If you’d like to monitor your charging, schedule charging sessions for off-peak times from your phone, or know exactly how much energy you’re using, you can opt for a smart charger with Wi-Fi connectivity.

To view different models and comparison shop, check out this buyer’s guide for home chargers.

Charging on the go

There is an increasing number of public charging stations available. Because they’re usually discretely located in parking lots, you may not have noticed them, but they can give you a little extra juice when you’re driving around town. Use mapping tools like PlugShare or ChargePoint to locate these stations when convenient.

Level I and II charging can deliver a full battery in the 6-8 hour window that most people are sleeping or working. This is fast enough to meet most daily driving needs. If you’re concerned about an empty battery on long road trips or emergencies, there is a solution: DC fast charging.

charging ahead webinar header
Although cars like the Chevy Bolt can only charge at a max rate of 24 miles of range per hour using Level II charging, DC fast charging can add 90 miles in 30 minutes of charging.

DC fast charging stations are available for public use and can deliver 50 kW of power the Chevy Bolt or as much as 150 kW for the new Nissan LEAF Plus – much faster than Level I or Level II. Depending on the vehicle and charging station, electric cars can recharge as much as 80% of a car’s total range in less than an hour. For more information, stay tuned for an upcoming blog on DC fast charging or read more at drivegreen.nationalgridus.com.

What is Drive Green with National Grid?

If you’re looking to reduce your gasoline costs, drive a smooth and quiet car, or do something for the environment, you’ve come to the right place.

Although electric cars are increasingly recognized as the superior technology compared to the gas-powered cars they’re replacing, the automotive industry has been slow to embrace the change. According to nationwide study conducted by the Sierra Club, nearly three-quarters of auto dealerships don’t even have a single electric car on their sales lot.

Furthermore, many salespeople do not understand electric cars, so they encourage shoppers to go with gas-guzzlers instead. As a result, car buyers who are curious about electric cars are likely to miss out on these vehicles with high efficiency, low fuel costs, and low maintenance costs. That’s bad for the climate and bad for consumers, too.

Drive Green with National Grid is a program that makes it easier for upstate New Yorkers to choose an electric car over a gasoline-powered car. When you walk into a dealership to test drive, you should feel confident that you’re talking to a knowledgeable salesperson who will give you accurate information about available purchase incentives, charging, and what it’s like to drive an electric vehicle (EV). So we’ve created a network of trustworthy and knowledgeable dealerships across upstate New York to make sure your purchase or lease process goes smoothly. And that network will grow with time!

EV specialist and
When you’re car shopping, working with a knowledgeable and enthusiastic sales person makes all the difference.

With our car comparison tool, you can easily explore different electric vehicle models to find the right choice for your lifestyle and driving needs. When you’re ready to test drive, you will be connected to an EV specialist at a local dealership with electric cars in stock. You can also use our website to learn about charging, find federal and state purchase incentives, and estimate how much money you’ll save when you drive on electricity instead of gasoline.

If you’re curious about the technology but aren’t quite ready to commit to visiting a dealership yet, we’ve got you covered! We also host events all over upstate New York to celebrate the benefits of switching to electric. Most drivers are concerned about charging availability or driving range of electric vehicles before they commit to one, so at these events, you can hear from real EV-drivers about why they love their electric cars and how their concerns faded away with experience.

Drive Green with National Grid is a collaborative program of Green Energy Consumers Alliance (a non-profit organization) and National Grid. Together, our goal is to educate drivers about the benefits of switching to electric vehicles in order to decrease greenhouse gas emissions and help drivers save on their transportation-related costs. Still skeptical about range, charging, or cost? You might be surprised to find out that you can make the switch to an electric car with little or no change to your lifestyle. Subscribe to this blog to learn more.