A new study reveals a massive difference between paid and free DC fast charging of electric vehicles in the United States, both in terms of energy dispensed and time spent charging.
According to a report from the Department of Energy’s Vehicle Technologies Office, EV drivers stay almost twice as long at "free" DC fast chargers than at the paid ones. That conclusion is based on more than 2.3 million sessions at non-Tesla DC charging stations between June 2020 and June 2023.
As it turns out, the average driver spends 78 minutes per session and gains 40.7 kilowatt-hours of energy at the free DC fast chargers. When they use the paid DC fast chargers, they spend just 42 minutes on average, while receiving a mere 22 kWh of energy.
So-called "free" DC fast charging is often thrown in as a perk with many EVs from Hyundai, Volkswagen, General Motors, Mercedes-Benz and other car companies. (I say "free" in quotes because the actual cost is often baked into the car itself.) In theory, this encourages people to buy EVs because they know they'll get free charging on their road trips.
In reality, it has presented several problems, including people only using DC fast chargers to "fuel up" as if they were a gas station; long lines to use those chargers; and long-term damage to batteries, since EVs generally should not be exclusively fast-charged. Our own Tom Moloughney has even called for this practice to end.
The most logical conclusion from this study is that EV drivers will take the opportunity to charge as much as possible at the free DC fast chargers, even if it will take them more than an hour, and probably 100%. It's crucial to remember that charging speeds usually decrease as EVs fill up, which inflates charging time quite noticeably.
In the case of the paid DC fast charging, the average time of 42 minutes—not far from typical up-to-80% charging times for modern EVs—indicates that drivers probably are using the charger more optimally. If the charging is paid, there is no point in charging more than needed to reach another charging point, thus wasting time on charging at a reduced power, or to reach home, where they can presumably get cheaper charging from an in-garage Level 2 charger.
These free charging programs may also significantly impact the availability of DC charging infrastructure in city areas, because the local EV community most likely will use the chargers more than they would if the service would be paid—especially if home charging is not an option.
The data set does not include the Tesla Supercharging network, but Tesla has officially revealed that the average session time (globally we believe) is around 27.5 minutes. Energy at the Superchargers is paid as standard, with some exceptions and promotions, and when combined with a relatively high power output (often 250 kilowatts) probably explains why the time is lower than average on the paid non-Tesla fast chargers. However, we believe that the average energy dispensed per session might be higher at Tesla Superchargers (it was less than 36 kWh as reported in August 2019.)
In any case, if you get a free DC fast charging deal with your EV, please make sure to use it responsibly, fill up only as you need, don't do it all the time and don't treat it like a gas station.
DC fast charging statistics, June 30, 2020, to June 30, 2023:
Data source: Energetics, EVWATTS Dashboard
* "The statistics in this study are from a self-selected set of EV owners nationwide. They do not include charging sessions from Tesla’s Supercharger network."