The Chevrolet Volt and Vauxhall Ampera both go on sale in the coming weeks. With a revolutionary new power system, incredible claims for mileage and carbon dioxide emissions, high-quality design and build and a soothing balm to the heart of range anxiety, both cars could be the answer to how we bridge petrol and diesel cars to all-electric cars - for a price that's knocking on the door of £30,000. The Volt uses a revolutionary technology that uses batteries to drive the wheels - you can charge these batteries using a socket you can plug into your electric sockets at home. Nothing new about that. But you can also use a small petrol engine to charge the batteries to drive the wheels when that charge runs out. And that's what makes the Chevrolet Volt a potential game-changer - along with its near-identical sibling the Vauxhall Ampera. In reality nothing changes - there's still a notional range to how far this car can go; when you run out of electricity and petrol you stop. But the perception that this car won't suddenly stop 70 miles from home - and you have a good old-fashioned back-up once this new-fangled technology runs out of puff - is an important one. The cost? Well, with a government plug-in car grant worth five grand, the Volt costs £29,995 on the road. A lot of money? Yep, but step inside the Volt and you're rewarded with executive levels of interior quality, good space, eye-catching layout and gadgetry that represents another big step on the way to making cars fully-functional computers. All the omens are good - but does the Volt actually work? Buying the Volt Chevrolt says it is gunning for private sales with the Volt and will virtually ignore fleet and business sales. Chevy has almost 100 outlets that will sell the Volt but special requirements for maintenance mean the Volt can only be serviced at 26 centres nationwide, which could provide a pain. The Volt costs £34,995 to buy outright but currently attracts a £5K government discount that brings it down to under £30K. Whether that grant remains in place indefinitely remains to be seen, but it could crucially bring it within range of private buyers who might otherwise be considering an executive saloon such as the Jaguar XF - or even motorists downsizing from SUVs. The Volt's styling is bold, different and rather eye-catching, I think, so GM's new toy ticks that particular box. The very low quoted CO2 figure of under 30g/km means the Volt is exempt from road tax and the London Congestion Charge too, which should ensure that Boris Johnson is setting up a photo opportunity as you read this. The Volt is powered by an electric motor that's driven by the charge in battery or cells - or by a small petrol engine. Chevrolet says that the Volt can manage 300 miles on a full charge and tank of fuel. Charging using a domestic 240V supply takes six hours. As far as fuel economy goes, Chevy quotes a figure of 270mpg from the European homologation centres that calculate such things. While it is possible to drive the VOlt in electri-only mode for much of the time, theoretically all of the time, I find this figure baffling and meaningless in equal measure; expect the Volt to achieve similar fuel economy to the Toyota Prius in real life, somewhere between 60-80mpg when driven carefully and until both batteries and fuel tank are empty. Voltec powertrain Essentially driving the Volt doesn't feel any different from driving any automatic - you turn the engine on using a Power button of the kind that is commonplace in cars these days, select the D for drive and push the gas. What is different is the noise - you probably won't detect much more than a whirr from the electric motor. In fact you probably won't notice any engine noise at all - at higher speeds wind and road noise will drown out the hushed motor. The petrol engine will supplement power from the battery from time to time - driving the motor directly along with power from the battery pack, if you're accelerating hard or up steep inclines for example. As well as the D-for-Drive position on the automatic gearbox there's an L setting too. You can select this to ramp up regenerative braking - the Formula One-like KERS system that recharges the batteries when the brakes are applied - which will mean a significant drag on the car's speed when you take your foot off the gas. In this mode you will feel significant drag on forward motion as the car recovers energy. It takes a while to adapt to but you should be able to drive the Volt without braking at all after a while when using this mode - and feel virtuous for doing so. The Volt will tell you how you're doing in terms of saving or expending power by means of a floating ball on the dashboard. Balance the ball in the middle of a vertical line and you know you're doing well - it brings a computer game aspect to driving the car. Volt interior The dashboard is a wonder of new instruments - with such a revolutionary powertrain there's much more data on the Volt's performance, range, acceleration and two fuel sources than a simple petrol or diesel car. It's a little overwhelming at first - and the Volt must have one of the most cluttered dashboards in the automotive world. But it's a very smart and pleasantly tactile one. The Volt I had on test drive was decked out in a stunning two-tone trim; materials feel very nice and the overriding impression is of high quality. Space in the boot is limited to 300 litres but can extend to 1,000 with rear seats folded down - though they don't fold flat. Driving the Volt Driving the Volt is a singularly serene experience. It's very comfortable and compliant, hushed at any speed and incredibly relaxing to drive. There's a Continuously Variable Transmission (CVT) to channel power to the wheels so there is no gear changing required. The CVT generally does a good job of balancing the revs. The driver need only worry about driving modes. On the other hand, if day-to-day driving conditions demand it, the Volt has plenty of grunt - 400NM of torque (around 300lb-ft in old money) are available if you need to overtake or suddenly accelerate. Of course driving the Volt hard rather defeats the purpose, the available available charge can fall noticeably from just a few seconds of hard acceleration, but it makes the Volt flexible and a viable alternative to a petrol or diesel engine rather than the hair shirt potential buyers might expect. The Volt has four driving model - Normal, Sport, Mountain and Hold - for a variety of driving situations. The latter enables the driver to preserve the full energy stored in the battery pack while driving on petrol power. As for range, well, I managed to get 42 miles out of the Volt's electric charge. Chevy says that around 50 miles is do-able so that seems impressive in real-world conditions and a mix of roads. I tried to detect the point where the Volt switched to petrol-generated electricity from the battery cells but couldn't. It was automatic, noiseless, seamless - the driver remains totally oblivious to all the complicated work the car is doing Chevrolet Volt - verdict Seamless strikes me as a good word for the Volt. It does everything asked of it without fuss and - fundamentally - without compromise. Driving the car is like driving any automatic car; there's very good space for four adults; it is not prohibitively expensive and there's sufficient interior quality and gadgetry as standard to coax executive drivers out of their saloons in search of low running costs. The Volt is not perfect. Boot space is limited and buyers may look askance at a list price that sets it alongside the entry-level Jaguar XF, BMW 5 Series and Mercedes E-Class. Just what the real-world fuel economy amounts to is something of a moot point - it's certainly nowhere near the quoted figures of 270mpg and 27g/km if driven until its petrol and electricity is exhausted. Having exhausted the electric power and half of the petrol tank my Volt registered 66mpg combined, but that figure had steadily fallen as the petrol disappeared. I suspect that by the time the petrol was used up that figure would have declined further by another 10-15mpg - but if you use electricity to charge the Volt and largely rely on just electricity to take care of your daily commute, school run aor shop then you can expect very low fuel bills. Whether that works for you will depend on whether you fit into the majority of commuters who travel less than 50 miles a day. If you do you could be quids in with a Volt - relying on the petrol engine as a back-up only will make the most economic sense. Despite the concerns this is a genuine alt-fuel car that sceptics can warm to. Its range may be limited to around 300 miles, but the back-up of the petrol tank should be enough to calm the range anxiety that EV-only cars seem to inspire. Cars like the Volt do require something of a step-change in thinking before they make complete sense. To make it pay you back you must drive it conservatively, be clever about where and when to charge, plan how you intend to use the car and think ahead to ensure the best return on that investment. Get in the car and turn on the ignition and it's clear the Volt is a car of the future - in more ways than one. Its styling is bold and interior suave, its technology futuristic, its powertrain frugal and incredibly clever - buyers may be convinced by any of those three reasons to invest in the Volt. The Volt is radical, yet it is not. It does not require the investment of faith and forethought that pure electric cars do - but it is a significant leap forward over standard petrol or diesel cars. The genius of the Chevrolet Volt is that it is both electric car and petrol car. You could drive it forever as a pure electric car - unlike hybrids such as the Prius - yet you can also drive it the length of the country should you wish in a way that would be realistically impossible in the all-electric Nissan Leaf. It is the best of both worlds and, as such, it is a marvel. For drivers in the Extended Range Alley - facing regular but relatively short commutes but requiring longer ranges periodically, fearing electric car ranges, seeking low running costs, desiring something different - it makes absolute sense. This is, in many ways, a very impressive car. Chevrolet Volt MILESTONES Price: £34,995 Powertrain: 150hp electric motor with 86hp 1.4-litre petrol engine through CVT Performance: Torque: 295lb-ft with both power sources; 0-60mph in nine seconds, maximum speed 99mph Range: 50 miles on electric charge; 300 miles total Quoted MPG: 270; CO2: 27g/km; VED road tax £0; BIK Company car tax five per cent