How did Tesla make some of its cars travel further during Hurricane Irma?

The electric-car giant gave customers a lifeline by remotely boosting their vehicles' battery capacity. But this act of kindness also highlighted that it had been selling identical cars at different prices

Tesla drivers who fled Hurricane Irma last weekend received an unexpected lesson in modern consumer economics along the way. As they sat on choked highways, some of the electric-car giant's more keenly priced models suddenly gained an extra 30 or so miles in range thanks to a silent free upgrade.

The move, confirmed by Tesla, followed the request of one Florida driver for a limit on his car's battery to be lifted. Tesla's cheaper models, introduced last year, have the same 75KwH battery as its more costly cars, but software limits it to 80% of range. Owners can otherwise buy an upgrade for several thousands of dollars. And because Teslas software updates are online, the company can make the changes with the flick of a virtual switch.