Renault's strategy of leasing batteries to customers who buy their electric cars is the best way forward because it keeps the purchase price down and gives peace of mind, said Thierry Koskas, Renault's electric vehicle programme boss.

Koskas said: "The purchase price of EVs with batteries would be too high. By leasing them at around £70 a month we can get the retail price of EVs down to the same level as the equivalent petrol or diesel cars with government incentives.

"It also means that when new battery technology comes along, owners will be able to upgrade their batteries."

The other advantage of a lease scheme is that it allows Renault to take control of the ‘second life' of the battery. One of example of this would be using the batteries to store solar-generated electricity at homes.

Koskas said that he expects government incentives to continue in some form across Europe for a few years. "Five years would be long enough for us to build big enough volumes - between 100,000 and 200,000 vehicles - to allow us to take advantage of economies of scale and start to reduce the price of EVs."

Both Fluence and Zoe, launched into the UK in early 2012, will have ‘quick drop' battery packs that are changed at purpose-built stations, he said.

Project Better Place is currently setting these up in Israel and Denmark.

"One of the advantages of quick drop is that it will allow battery use to be mitigated. A high-mileage taxi, for example, could have its battery swapped with one from a low-mileage family car that is the same as leasing companies do with cars. We are convinced by this model."

Battery swaps work much like a car wash with a service bay cut out from underneath. The customers drive their Renault electric vehicle into the bay and a robotic arm unclips the spent battery and replaces it with a fully charged one. Renault UK said it was possible, but unlikley the battery swap would be a technique used in the UK.