Shai Agassi, the California-based software superstar who wanted to run SAP but left the company in March when he didn’t get the top job, has come back into the spotlight as the CEO of an electric car start-up. The new company is funded by $200m of venture capital and investment bank money. This makes it one of the best-funded start-ups in history. Agassi does not intend to make electric cars. Wisely, he is leaving this to the auto industry. He is focusing on the batteries. He’ll lease them to anybody with an appropriate car and he’ll develop large networks of ‘filling stations’ where the driver can quickly take out a discharged battery and swap it for a fully charged version on long journeys. By 2010, he wants a hundred thousands electric cars on the roads of California and elsewhere.

The obstacles are huge. Although lithium-iron-phosphate battery technology is improving rapidly, and will continue to do so for decades, full-size car batteries now cost at least €7,000. Getting mainstream manufacturers to build large volumes of electric cars that will take his batteries is another formidable challenge. Third, he has to persuade retailers to install the equipment to swap batteries automatically.

But our weary European scepticism needs to be rested for a moment. The long-run economics favour this idea. My sums suggest that at current UK petrol prices it costs at least six times more to drive a mile on petrol than it does on electricity. Battery prices will fall and performance will improve. At some point it is going to be so much cheaper to power a car with electrons rather than octane that even the slothful auto industry will switch. When the market has tipped it won’t be long before passenger cars are all electric. Agassi may be too early, and his business model may require too much capital, but electric cars are coming soon.