Both Jane O'Leary and Raymond Brock are among many readers of The Independent's Motoring section who are interested in the G-Wiz. This is an electric car that runs on batteries and they want to know everything about it.

Apparently, this is David Cameron's favourite car. Well, it was the other week when he was photographed driving it around an airfield. So here goes.

Essentially, the Reva G-Wiz is being sold online by a company called GoinGreen, which says that the G-Wiz is the cheapest car to own, with no road tax, no London congestion charge, free parking in central London, 600mpg equivalent and group one insurance.

It reckons that the congestion-charge savings alone pay for the monthly finance payment, if you buy on credit. That brings us to cost. The retail price is £8,299, but, for a limited period, you can purchase a G-Wiz for the special price of £7,799, saving £500.

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The bottom line is that this is claimed to be the greenest and cleanest car available, being emission- free and carbon-neutral. The company even "carbon balances" the manufacture, shipping and first two years' driving of the car. It is made in India, although it is the brainchild of a US entrepreneur who realised that one of the main obstacles to making a viable electric car was the cost of manufacture, hence the choice of location for the factory.

Trouble is, the G-Wiz is a spectacularly ugly vehicle not very practical or comfortable. Although it has two reasonable front seats, the rear ones are really only suitable for very small children. It holds its own in stop-start traffic in town, but it won't go much faster than 40mph, which limits its range and effectiveness. There is also a still stranger and more expensive electric three-wheeler called the Twike, which you steer via a joystick and can also pedal, should the need arise. However, these cars represent hair-shirt motoring for yoghurt-knitters. I believe there are better options if you want a proper car that is cheap to run and environmentally friendly.

A CAR FOR THE HEAD

A Smart. Like the G-Wiz, it is stubby, but at least looks as though someone has bothered to actually design it. It is also a safe car, with airbags, a safety cell, ABS brakes and stability control. You can also get grown-up features such as air conditioning and heated seats, never mind leather trim.

The Smart never feels out of its depth on the open road. The emissions aren't too bad, either. The Toyota Prius, which is the Holy Grail for greenness, registers 104g/km for CO2, whereas the Smart is 113g/km. The Prius, though, costs almost £18,000 and the ForTwo starts at less than £7,000, so at least you save your money, never mind the planet.

However, this newspaper, in the "Your planet and how you can save it" series, judged a Smart car converted to run on LPG (liquid petroleum gas) as the most environmentally friendly, beating the Toyota Prius and G-Wiz. Its emissions are around 90g/km.

Not only that, the LPG Smart is exempt from the congestion charge, being eligible for a 100 per cent discount on London's congestion charge....