BYD's outpacing of Tesla has only just begun

One electric-vehicle challenge Elon Musk saw coming in his rear-view mirror has just edged past him. On Wednesday, BYD clocked quarterly sales that handily beat Tesla. The next worry is that his Chinese rival will keep pulling further ahead.

BYD's top line was neck and neck with Tesla's in last year's fourth quarter. But it powered ahead in the latest results, with a record 201 billion yuan ($28 billion) in revenue in the three months to the end of September, some $3 billion more than its U.S. rival's.