Tesla's road less traveled

To date, electric cars have been a niche market - a result of their relatively high prices and limited driving range. They account for about one percent of total vehicle sales in the US and two percent worldwide. In the US, half of all e-cars are sold in California, which has long required carmakers to sell a proportion of zero-emission vehicles in the state.

Costs are increasing in the US for e-drivers. Some 17 states currently charge fees for electric vehicles. This is also intended to help the electricity sector to contribute to transport infrastructure. California, for example, has called for a fee of $100 from 2020.

Since launching its first automobile in 2008, Tesla - which now has 30,000 employees - has become a leader in making eco-friendly cars, a 'disruptive' Californian company that could go on to dominate a new industry. And Musk has already gone further than in the car industry predicted since the launch, six years ago, of the Model S.

Some are wary as Tesla hasn't updated the number of Model 3's on back order for more than a year. Charley Grant, who covers Tesla for The Wall Street Journal's "Heard on the Street" column says demand for Teslas could be softening as competitors roll out electric models, like Chevrolet's Bolt. The Model 3 backlog is about 400,000.

As China builds its own battery plants, maintaining cost advantage may be difficult. Beijing wants at least 8 percent of a sales in China to be zero-emission vehicles from next year. Tesla's Model 3 has already been beaten to market in the US by GM's Chevrolet Bolt, while VW will spend $10 billion on transforming into an e-car company by 2019. Ford and BMW are doing the same.