Tesla vehicles at the company's store in Warminster, Pennsylvania. Joe Lamberti/Bloomberg/Getty Images

Tesla is set to report its best quarterly earnings so far this year. What lies ahead is the problem.

Analysts forecast that the company on Wednesday will report adjusted earnings of about $1.9 billion, driven by record sales of nearly 500,000 cars during the quarter. But that falls short of the $2.5 billion Tesla earned a year ago, a sign of the headwinds the company faces.

The company’s third quarter sales surged as Americans rushed to buy electric cars before a $7,500 federal tax credit expired on October 1. But American electric vehicle sales are widely expected to plunge in the fourth quarter because people who would have normally bought later in the year purchased early to

See Full Page