Shares of Tesla Motors shot up after the close of trading Wednesday when the company forecast that its sales would soar 55 percent this year. A Tesla car is parked near the Washington state Capitol in Olympia, Wash. (Rachel La Corte/AP)

Shares of Tesla Motors, which has combined a dose of optimism with high-quality electric luxury cars, shot up after the close of trading Wednesday when the company said that it sold and delivered 6,892 Model S cars in the fourth quarter of 2013 and forecast that sales would soar 55 percent this year.

Tesla also said that it would accelerate design and engineering work on its Model X sport-utility vehicle, which it expects to start delivering to customers in the spring of 2015. Tesla chief executive Elon Musk said advance orders were already coming in.

“It’s like if you’re going fishing and the fish are jumping in the boat,” Musk said. “We’re not trying to sell the model at all, but demand is high and we’re seeing the accumulation of Model X deposits.”

Tesla’s stock, which jumped nearly 12 percent after hours, has now soared fivefold in the past year. The stock market valuation of the company is now roughly half that of General Motors, which had about 75 times as much revenue and billions of dollars in profit.

Tesla said that it narrowed losses in the fourth quarter to $16.3 million on $615.2 million in revenues. That revenue included $15 million — or $2,176 per car — from the sale of federal regulatory credits intended to promote the sale of electric vehicles.

For the full year, Tesla lost $74 million on revenue of $2 billion, an improvement from 2012, when it lost $396.2 million on $413.3 million in revenue. Revenue from lease sales is not included.

Tesla delivered 22,477 vehicles in 2013 and expects to sell more than 35,000 this year. The price of the Model S begins at around $71,000 and rises substantially with options.

Musk has sought to boost sales with free recharging stations, leases and guarantees of resale value. In late January, Tesla publicized a company team that braved snowstorms and completed a coast-to-coast trip in just over 76 hours using only the company’s charging network.

Musk said that while sales dropped after a Model S caught on fire in an accident, consumers concluded that the risk was greater in a conventional gasoline-powered combustion engine, and sales resumed at their earlier pace.

Tesla said that it slightly surpassed its target for gross margins, by “reducing vehicle cost, primarily through component cost reductions as well as increased manufacturing and supply chain efficiency.” Its closely watched gross margin — profit before research and development, sales and administrative costs — exceeded 25 percent.

While Tesla still relied in part on federal credits, it did not receive any revenue from the sale of “zero-emission vehicle credits” under a California state program to promote electric vehicles, previously a much larger source of revenue. Other automakers that needed to purchase the state ZEV credits in earlier quarters have now introduced more of their own low-emission vehicles.

The company said it generated $40 million in free cash flow, boosting its cash on hand to $846 million, boosting investors’ confidence that the company can continue to expand and ride through obstacles.

Production of its Model S cars will climb from 600 a week to 1,000 a week by the end of the year, the company forecast, with most of the increased sales coming in Europe and Asia. Musk said that “it is unlikely that we’ll be able to satisfy demand in China.”

The company’s lithium-ion battery supply shortage “will continue to constrain our [vehicle] production in the first half of the year.” But Musk said Tesla would reveal plans for its “Tesla Gigafactory” next week. The company’s earnings release said that the new plant would “allow us to achieve a major reduction in the cost of our battery packs and accelerate the pace of battery innovation.”

In any electric vehicle, the battery makes up a huge part of manufacturing costs.

Musk said that its current battery partner, Panasonic, would be one of — but not the only — partner in the new plant. He said the plant would be “heavily powered by renewables.”

Tesla’s shares closed Wednesday at $193.64, down 5 percent. After the close of regular trading, and the earnings announcement, Tesla’s shares jumped to $216.41, up 11.8 percent.