Elon Musk said on Tuesday he plans to remain chief executive of electric-car maker Tesla Motors Inc. for at least another four to five years, and then reassess whether he would continue in the post, reported The Wall Street Journal.

Mr. Musk, speaking to shareholders at the Palo Alto, Calif., company's annual meeting, said he is committed to staying through the start of high-volume production of Tesla's coming third-generation car, which the company would like to start producing at the end of 2016.

"It is quite difficult to be CEO at two companies," Mr. Musk said, when asked by a shareholder how long he would stay. Mr. Musk also is CEO of Space Exploration Technologies Corp. and the chairman of solar-panel supplier and installer SolarCity Corp. "I will stay four or five years, then it's TBD after that."

Shares in the auto maker were up 24 cents at $204.94 in 4 p.m. trading on Tuesday on the Nasdaq Stock Market.

Dozens of shareholders turned out for the meeting, held at the Computer History Museum in Mountain View, Calif. One shareholder asked for a job as vice chairman, another said he made enough money to buy a Model S by day-trading the stock. The luxury electric vehicles start at about $71,000.

Mr. Musk also said Tesla may start construction on as many as three separate sites for its giant battery factory, after saying earlier that work would begin on two sites. Site work is supposed to start on the first of several sites for the so-called gigafactory this month.

To meet construction deadlines, Tesla plans to start construction at several different locations, despite having not chosen a final spot. Mr. Musk said the final location likely would come at the end of the year. Tesla is scouting sites in California, Nevada, Arizona, New Mexico and Texas.

He also said he was "quite optimistic" that Tesla could achieve a greater than 30% cost reduction compared with today for battery packs through the construction of the gigafactory, and that partner Panasonic Corp. now was in agreement.

"Panasonic at first wasn't sure these cost reductions could be achieved, but I think they are now," he said. Panasonic recently said it hasn't yet decided how much it will invest in the giant battery factory, which would be the world's largest.

When asked about why other auto makers hadn't followed Tesla with longer-range electric cars, he said he was surprised. He also hinted that he was planning a "controversial" announcement dealing with some of Tesla's technology patents.

Looking to the future, Mr. Musk said the company might look at building a truck because of the potential to displace fossil fuel. It is an idea he has mentioned before.

Mr. Musk also related a story about the naming of the company's coming third generation car. Tesla had trademarked the name Model E in part because along with its coming Model X sport utility, the company's models' names could form the word sex. Tesla also considered trademarking "Model Y," he said, which would allow for vehicles using the letters s, e, x and y.

"But Ford called up and threatened to sue us," Mr. Musk said. "It was like, oh my God, Ford is killing sex!"