By Grace Yoon

Shares of Rivian fell as the electric vehicle maker said it planned to sell 75 million shares of common stock to help pay back a loan from the U.S. Energy Department.

The stock was down 12% to $17.73 in recent trading and has fallen 9.2% since the start of the year.

As part of the public offering, Rivian will grant underwriters the option to purchase 11.25 million additional shares within 30 days.

Rivian also reported on Monday it expects factors like a lower average selling price of its cars to hurt its second-quarter revenue. The company said it anticipates revenue for the quarter, which ended June 30, to be between $1.55 billion and $1.65 billion.

Write to Grace Yoon at grace.yoon@wsj.com