In the USA, the upcoming Thanksgiving weekend will see a post-covid new surge of long distance travel on Wednesday and Sunday afternoons. This may create an issue for the new millions of electric cars taking long trips. While the world has had over a century to build up gasoline networks, EV charging for long trips is a relatively new phenomenon, and many facilities to handle such a peak have not been built.
There are probably around 600,000 new Teslas alone since 2019. On the other hand, Tesla has also more than doubled the number of Supercharger stations globally since then. Non-Tesla EVs, though much smaller in volume than Tesla, have also been growing quickly, and non-Tesla stations, sometimes known as DC-Fast or just CCS stations, have also been growing at an even faster rate.
There were 792 supercharger stations 3 years ago and over 1,900 today with a total of over 21,000 stalls. Figures from June suggest there are now well over 5,000 CCS stalls for non-Tesla cars (Most Teslas can use these with an adapter.) CCS stations have far fewer stalls than Tesla ones, on average.
Thanksgiving 2019 in the California central valley saw the confluence of multiple bad factors resulting in massive multi-hour lines at some chargers in the central valley. A storm which bunched up traffic and the Thanksgiving surge created more demand than Tesla’s system could handle. At the same time, most other stations, while heavily used, were not overwhelmed. Indeed, rural charging stations used for road trips tend to be less used most of the time than urban stations, even though EV drivers who charge at home almost never use urban stations, and only use rural ones when they take long trips.
The operators of the charging networks have been beefing them up. Thanks to massive grants in the Inflation Reduction Act they will be adding a lot more of them, though people wonder what happens as the world switches to EVs — California and some other states have already passed laws requiring new cars to be EVs by 2035, and several automakers, such as GM, have announced plans to go all-electric. Most driving, around a person’s home city, should be powered by charging at night and in the morning, at homes and commuter parking lots, but long-distance driving needs rural fast-chargers, and Thanksgiving will probably be the peak demand point.
Softening a peak
There is always a challenge in provisioning resources around a peak. You can provision to handle the peak with ease, but that’s expensive and you are way oversupplied the rest of the year. It’s more common to provision to be a little overloaded at the peak and handle the extra demand with other techniques.
One trick Tesla has done in 2021 and this year is to offer free charging at their superchargers in the off-hours during the Thanksgiving weekend in 4 states, including California and Texas. But offering free charging, they hope to encourage people who don’t charge at home to charge up in the early morning, which will reduce load during those peak afternoons and evenings. This is a “demand side management” technique that has been used by electric utilities for decades.
This is one thing gasoline does better. The speed of filling a gas tank means that it’s easy to handle a surge in demand. Lines at gas stations do happen — sometimes horrible ones when there is a shortage — and they happen at Costco all the time due to low prices. But it’s harder for EVs to get through it.
Many people will take trips within the range of their cars — 250 to 300 miles for Teslas. Knowing the big day is coming, they should charge in advance and make the whole trip Wednesday without needing to charge. When they get to their destination, they can charge-up again mid-weekend — perhaps even with just a regular household plug or at a less loaded fast charger — and be ready for the return. They may even get the charging free from Tesla if that’s convenient.
A much smaller number are driving that far — more than 4-5 freeway hours. For them, a good plan is to charge up full, and try to recharge at a station when they get down to below 10%. Cars charge fastest when they are low. This will probably be a rural location. Some networks, like Tesla’s, let drivers see how many stalls are free at all the stations, or if there is a wait.
The useful result is that because Thanksgiving travel is almost entirely planned well in advance, while day to day travel is more random. Just as all air travelers and the airlines know the rush is coming, so do drivers.
Tesla’s design with much larger stations handles surges better. Even if the station is full, new stalls open up frequently to minimize risk of wait. Stations with 2-4 stalls can have a serious risk of wait since each car will spend around half an hour. With more stations, these networks do make it possible to leave and get to another station, but they don’t make it easy to figure out which stations might have the shortest waits.
To manage peaks, charging networks might do well to support “virtual” lines where people can get in line digitally as long as they know they can show up when it’s their turn. Butcher shops have had people take a number for centuries, but EV charging stations haven’t seen enough trouble to implement this yet, though it’s one way to handle a peak demand surge.
Some charging networks also need to resolve problems they have had with station reliability. Because EV charging is not a business the way gas stations are, outages have been notorious even not at the peaks. Ideally the networks have made a special effort to bring everything up to operational levels for the Thanksgiving rush.
EV drivers do have to deal with the fact that range can be lowered when their battery is cold — though again, if one plans, the battery will be heated in advance and fast charging and driving keep the battery warm. If they do get stuck in traffic, they have the advantage that they don’t have to run a motor to keep warm. Newer EVs use heat pumps for heating which are highly efficient and can keep a car warm for days on the battery if it should come to that.
While the data above suggest there are more chargers out there per car than in 2019, and thus problems should not be greater than before, some sources suggest the number of cars per charger has increased. If so, we might see some trouble spots. Stay tuned for the after-Thanksgiving reports.