Elon Musk added US$1.4 billion to his fortune Tuesday with a single tweet.

Shares in Tesla Inc. climbed 11 per cent to US$379.57 at 4 p.m. in New York, taking Musk’s fortune to US$25.8 billion after he said he’s considering taking the electric-carmaker private at US$420 a share.

His missive came minutes after the Financial Times reported that Saudi Arabia’s Public Investment Fund had built an undisclosed stake of 3 per cent to 5 per cent this year, citing people with direct knowledge of the matter it didn’t identify.

Musk’s tweet said he’s secured funding without providing details. A price of US$420 a share would value the company at US$82 billion including debt. Even as the world’s 31st-richest person and Tesla’s largest shareholder, Musk would be reliant on outside funding for any buyout since his fortune is highly illiquid. The chief executive officer said in an email to employees that shareholders would have the final say if he decides to follow through on going private.

About half of his US$26 billion net worth is held through his stake in Space Exploration Technologies Corp., which the billionaire has vowed to keep private until it starts making regular missions to Mars, which is years from now. His US$13 billion Tesla stake would presumably be rolled into the private enterprise. Musk, 47, has already pledged some of his shares of Tesla’s common stock to secure bank borrowings, according to a June 2018 filing.

A buyout at US$420 per share probably won’t let Musk reap any benefit from the US$2.6 billion stock option grant he received this year. At that price, the value of the shares alone comes to US$72 billion, falling short of the initial performance hurdle of US$100 billion. That means the securities would be forfeited.