A late change in the transmission vendor "was a big thing for us to do in the program, very painful, and one of the things that has driven us into a little later this year release of the car", Eberhard said.
The Silicon Valley-based Tesla has pre-sold 570 cars to the likes of California Governor Arnold Schwarzenegger, for his wife Maria Shriver, and actor George Clooney. The company will make a thousand of the 2008 model year cars.
The Roadster, which has a base price of $127,500, can go hit 100 km/h four seconds and has a range of more than 320 kilometres on a single charge on a household plug.
Eberhard and co-founder Marc Tarpenning launched Tesla in 2003 with the idea of making a high-performance electric vehicle and then branching out to more affordable cars later on.
Since then, Tesla has secured $105 million in funding, with PayPal founder and space industrialist Elon Musk leading the way and venture capital firms joining in recent funding rounds.
With delivery of the car approaching, Eberhard said: "We have a lot more interest in investing in this company recently."
Eberhard said that if they just limited production to the Roadster, Tesla would be making a profit in 2008.
"But Tesla's intention has always been to grow to be a full-fledged car company as quickly as we can do that," he said.
"We are taking everything we earn from the Roadster and everything we have raised from outside sources to build the next model car."
The next car will be the White Star, a five-passenger sedan at around half the sportscar's price point, to be manufactured in New Mexico.
"We are in the very early stages of it," said Eberhard, noting that he "would not place any bets" on a target of a 2010 model year.
That same year, General Motors Corp
