Can Electric Vehicle Owners Rely on DC Fast Charging?

There are two types of public charging. Level 2 is a 240-volt charger that’s similar to the one EV owners typically install in their homes. A Level 2 charger usually charges an EV at a rate of 20 to 35 miles of range per hour. These are also known as destination chargers because they are appropriate for when you’ve arrived at your destination and plan to spend several hours there working, visiting, shopping, or dining. But a Level 2 charger is not appropriate for charging on the go when you’re on a long interstate trip.

The speed of DC fast charging is determined by the car’s maximum acceptance rate in terms of power in kilowatts (kW). That spec is up to the manufacturer to choose based on the vehicle’s electric architecture and battery management priorities. Current EVs span in their maximum charging rate from 50 kW for a Chevrolet Bolt to 300 kW for the Lucid Air. 

• We conducted the experiment in two sessions, in two different Electrify America locations in Connecticut, a month apart on Aug. 30, 2022, and Sept. 28, 2022. 
• Prior to each session, we prepped the cars so they would arrive at the DC fast-charging location with exactly 30 percent battery level.
• For the Model Y we used the Tesla Supercharger network at two different locations; while Teslas can also be charged at Electrify America by using an adapter, in the real world, Tesla owners by and large use the Superchargers, rather than the chargers from another provider. 
• We stayed plugged in until each car reached 80 percent SOC and recorded the time it took.
• Throughout each session, we monitored the charging rate in kilowatts against the battery’s state of charge and noted whether it matched the manufacturer’s claims.

As illustrated by the infographics, the Ioniq 5 and Model Y gained the most charge per minute. Hyundai claims 235 kW maximum acceptance rate, and we observed 236 kw in the first session. But with the Tesla, the company claims 250 kW; the best we observed was 230 kW. Those charging speeds are a major advantage on a road trip because it shortens your pit stops and it lets you get back on the road sooner. 

The Mach-E’s claimed max acceptance rate is 115 kW (we observed 114 kW in the first session, and less in the second one). Even though it doesn’t charge as fast as the Ioniq 5, it gained more miles of range when going from 30 to 80 percent state of charge because of its larger battery (88 kWh vs. 77.4 for the Ioniq 5). 

Our early version of the VW ID.4 is supposedly capable of accepting a maximum of 125 kW power. Since we bought our ID.4, VW has upped that spec to 170 kW for 2023 models. There is no over-the-air update. We observed a peak charging rate of only 91 kW in one session and even less during the second session. 

The results show that there is variation in how rapidly cars charge and how close real-world charging rates align with the manufacturers’ claims. And speeds can vary by location. 

Currently, there are only about 6,000 DC fast chargers in the U.S. They span between 50 kW and 350 kW of power. In our experience, the most prominent and easiest to use belong to the Electrify America network. Most venues, including those with EVgo and Applegreen charging stations, have four to eight stalls. The majority of the Electrify America’s chargers have an output of 150 kW, but often two stalls have more powerful 350 kW chargers. Activating a charger can be done through an app linked to an account that has a credit card on file and reloads payment automatically, like an E-ZPass account. Alternatively, one can pay by swiping a credit card at the charger. 

Electrify America’s rate is 43 cents per kWh for guest and Pass members. For $4 per month, you can become a Pass+ member and pay a discounted rate of 31 cents per kWh. Tesla raises its pricing more frequently and doesn’t have a uniform national rate. It charges more in California for instance, where gas prices are also higher.

Tesla was a pioneer in the DC fast-charging arena. It set up a proprietary network in easy-access rest areas right off interstate highways. And the chargers work seamlessly. Simply pull up to the charger and plug in. Charging starts immediately without the need to fumble with an app or a credit card. You have to have a credit card on file with Tesla, and you get billed afterward with an email notification. In this regard, Tesla nailed it. These locations are typically in busy, well-lit areas with accessible public restrooms around the clock. Currently, there are approximately 2,000 Tesla supercharging stations in the U.S.

Other networks, Electrify America included, are often located in less desirable locations, like a strip mall, in some cases next to a Walmart and mediocre food choices. These locations require getting off the highway and often seem stranded and off the beaten track. For restrooms, one has to rely on nearby business establishments, during open hours. 

In the vast majority of DC fast-charging places, regardless of network, and unlike a typical gas station, there is still a lot to be desired in terms of services. For example, there is no overhead canopy to shield customers from the sun or rain, no handy squeegee to clean the windshield, and no nearby trash or recycling bins to dispose of wrappers and empty bottles people collect during a long trip. 

During our sessions, we saw a microcosm of the DC fast-charging scene that should be taken as a cautionary tale of things to come. We encountered frustrated EV drivers who had difficulty activating the chargers. We saw Bolt and Niro EVs plugged into a 350 kW charger, which has no benefit for them because of the vehicles’ limited acceptance rate, taking up a spot from another EV that could benefit from the higher power. We witnessed arguments between drivers who thought they were next in line. We observed an EV plugged in for a long time, already at 93 percent SOC, monopolizing a charging spot with no driver/owner in sight to unplug and clear the spot for the next vehicle in line. As EVs become more popular, we see these issues as looming problems that need to be rectified. 

Striking a conversation with fellow EV drivers reveals their modus operandi as it relates to long trips and fast charging. A couple driving a Hyundai Kona EV from Boston to Atlanta told us that they don’t mind the tradeoff of long and frequent stops to charge. They noted that they are retired and were in no hurry and would rather benefit from driving electric, but still wished the car would charge faster. 

A couple driving a Tesla Model X from New England to Florida raved about the Tesla’s navigation system that charts out a route and determines at which Supercharger location to stop. It even preconditions the battery for optimal charging right before approaching the charger. This couple didn’t mind the charging stops because they had a dog to walk anyway. 

Other EV drivers told us they came to get a charge on their lunch break because they had the opportunity to do so, because their home charger was broken, or because it was cheaper for them to fast-charge at a public place than charge at home. Or, because they never installed a home charger. (Find out how to choose the best home wall charger for your electric vehicle.)

There is a bipartisan infrastructure law that allocates $7.5 billion to develop public EV charging infrastructure that will add 500,000 public charging stations that will include both Level 2 and DC fast types. That may not be enough if the issues we witnessed become worse as EVs gain more popularity and as some states mandate EV sales starting in 2035. 

For its part, Electrify America announced it will roll out a new generation of charging stations with clearer markings for 350kW units. The company is also planning on adding awnings for shade and shelter from rain, as well as security cameras.