Why Public EV Chargers Almost Never Work as Fast as Promised

For EV drivers traversing the great state of Wyoming, the Smith’s grocery store in Rock Springs is an oasis. It’s just off I-80, there’s a Petco across the street, and it has six plugs promising to charge at 350 kilowatts. At that rate, a Tesla Model 3 could go from empty to full in the time it takes to hit the bathroom and grab a Snickers.

But when I limped up to the station last month — in a Rivian R1S crammed with one dog and two kids — that 350 kW may as well have been a mirage. Rivian’s SUV charges at 220 ...