Tesla's Elon Musk has poked fun at short sellers as his electric-car maker's stock surged to a record, vaulting its market value past century-old rival Ford.

"Stormy weather in Shortville..." the chief executive officer tweeted on Monday US time, as Tesla shares climbed as much as 5.8 per cent. The maker of Model S sedans and Model X crossovers saw its capitalisation surge to about $US48.2 billion ($63.4 billion), $US3.1 billion more than Ford, the No. 2 car maker in the US after General Motors.

Tesla has long been a popular target by short sellers such as Jim Chanos, who famously bet early on energy company Enron's failure - and was proved right. Short interest in Tesla has risen to 29 per cent of its free float from a 52-week low of 20 per cent in mid-October, according to Markit data.

Tesla's move past Ford came one day after Musk's company reported worldwide shipments of 25,000 cars and SUVs in the first quarter, exceeding analysts' estimates. While Ford delivered about nine times as many vehicles in just the US last month, its sales missed projections and the shares fell.

"I don't know if people want electric cars, but people want Tesla," said Ben Kallo, an analyst at Robert W Baird & Co. "I'm not an Elon Musk worshipper, but people that would normally buy a Porsche are buying Teslas right now."

Ford, which reported net income over the past five years totaling $US26 billion, towers over Tesla on most metrics. Tesla lost $US2.3 billion during the same five-year span. Revenue was $US151.8 billion last year for Ford, compared with Tesla's $US7 billion.

Tesla sold about 40,697 vehicles in the US last year, according to registration data compiled by IHS Markit. Ford delivers that many F-Series trucks about every three weeks.

'Star power'

But Tesla has long been valued like a technology stock, in part because of what Kallo called Musk's "star power". Also the CEO of rocket manufacturer SpaceX, which has grand plans to colonise Mars, Musk has demonstrated his pull on Wall Street. He's raised about $US8 billion from equity and debt offerings since 2010, according to data compiled by Bloomberg.

Kallo is convinced Tesla has the ability to achieve its ambitious goals.

"They're a better car manufacturer, they attract better talent and they have more things going on beyond their four walls than we know about," he said. "Worn-out industries where people don't make money is the opportunity for companies like Tesla."

The Palo Alto, California-based company has yet to prove it can manufacture in high volumes. Tesla's brand ranked No. 30 in the US in terms of sales last year, according to researcher Autodata.

But investors are looking far ahead to the Model 3, a sedan that will retail for about $US35,000, compared with $US68,000 for the least-expensive Tesla available now. Musk has predicted that with Model 3 in the lineup, the company's annual production will ramp up to 500,000 by next year.

Tencent stake

Among the believers is Chinese Internet giant Tencent Holdings, which bought a 5 per cent stake in Tesla last month, giving Musk a key adviser as he tries to crack the world's largest car market.

"The only thing that matters for the stock this year is Model 3," said Joseph Fath, a fund manager at T Rowe Price, Tesla's fourth-largest shareholder.

As Tesla tries to crack the mass market, the company will start to look more like a conventional car maker and will have a tougher time justifying its value, said Maryann Keller, an auto industry consultant in Stamford, Connecticut.

As sales grow and Musk pushes beyond luxury buyers, he'll have to add factories, retailers and staff to service cars. Plus, Keller said, there hasn't been much demand so far for mass-market electric cars.

Day of reckoning

"This is still the auto industry," she said. "It's highly competitive and he will have to add plants and people just like GM and Ford do. There will be a day of reckoning at some point."

Dozens of other companies around the world have battery-powered cars on the market, and more are in development. Investors "act as if Tesla has some sort of patented product that cannot be replicated", said Dave Sullivan, an analyst at researcher AutoPacific.

"By the end of this decade, there's going to be some significant choice for consumers looking for an electric vehicle," he said, calling Tesla's valuation outpacing Ford's "mind boggling".

Ford, which is planning to spend $US4.5 billion expanding its fleet of electrified vehicles by 2020, is getting an intimate look at what it's up against. A year ago, the company paid $US199,950 - $US55,000 more than the sticker price - to buy one of Tesla's first Model X SUVs for internal testing.

Bloomberg