It’s not often that a major car company risks its future by trying to change the world and challenge its customers to come with them.

Mercedes-Benz half tried it with the Smart range and the A-Class, but still only put a toe in the water. Audi half did it with the A2 then backed away, while Toyota half did it with the Prius. All of them burnt fuel somewhere in the mix so that they didn't shock anybody too much.

But a wholesale change and a big risk is what a nervous BMW is taking with its all-electric i3, due on sale in Ireland late this year at a price somewhere near the bottom end of the 5-Series range.

And it hasn’t just made an electric car in the i3, it’s invented an entirely new way to build a car and BMW has given the battery an eight-year, 100,000km warranty, which indicates the sort of annual mileage it’s expecting from its new electric baby.

Every BMW or Mini shares at least half of its parts with at least one other family member. Not the i3. The only significant thing it shares is its steering, which comes off the next Mini, and its multi-media system. BMW developed a mega-strong aluminium frame to house the i3's 230kg battery pack beneath the floor, in the deepest, most secure part of the car, nestled inside all the wheels. Only brands like Lamborghini and McLaren use carbon-fibre chassis and the material has stayed in the supercar realm because it's so expensive – it's slow and difficult to produce in significant numbers.

BMW wants to build about 30,000 i3s a year and all of them will have a carbon-fibre, five-door body that is essentially a second chassis dropped on top of the aluminium frame. That’s not low volume, but it does make the i3 about 30 per cent lighter, at 1195kg, than it would be with a conventional design.

But while this twin-chassis, breakthrough-engineering philosophy won't hurt BMWs technical image, it doesn't help the price. BMW will be asking between €35,000 and €40,000, which is significant. There are bigger cars with greater range and very low fuel consumption in the BMW lineup, without having to head to other brands. And that's saying nothing about when you go to change over your i3 into a used car market that doesn't have any baseline for it.

Conventional interior
If they started from scratch with the chassis and body engineering, they tried hard to keep the interior conventional. The i3 has a high driving position and, with no transmission tunnel, it has a flat floor that helps improve the impression of space.

That moves you to the front seats, where you find they sit taller than the current B-Class Mercedes-Benz but feel extremely comfortable and are very lightweight. Electric operation has been overlooked for weight reasons but that’s not a hardship.

BMW kept a cover over the interior design when we drove the car this week, but there is a high-mounted, multi-media screen topping the centre of the dashboard and a digital speedometer that also shows whether the batteries are being charged or discharged.

There are large storage areas in the dashboard, including an open one on the top, beneath the multi-media screen and a deep, capacious glovebox. That’s just as well, because the cargo area is tinier than Mini-tiny.

It has a lot of headroom and spectacularly good vision that is like an SUV, but airier.

The rear seat is a different matter. Yes, it’s an easy place to sit and it has plenty of headroom, excellent forward visibility and very comfortable seats – and it’s wide enough for three – but it’s not without its issues.

The biggest of them is the rear-hinged doors. They create a very easy way to lean in to drop bags or tend to children but they’re a little awkward to get in and out of with any dignity. The bottom edge of the door frame tilts up a little earlier than it might (presumably to accommodate the rear wheel) and you have to step up and twist around it.

But the biggest problem in the i3’s packaging is its boot space. BMW isn’t releasing figures on the actual capacity of it yet but after you’ve put one large sports bag inside, the rest of your luggage had better be of the small space-filling type.

Most of the instruments are exactly where you’d expect them to be, with an “On” button as well. The i3 introduces a control unit on the right of the steering column that twists forward for drive, back for reverse and half a click for neutral.

And then you just push the accelerator pedal and move off as fast or as gently as you’d like. It’s a remarkable feeling, sailing off in the i3. It’s a little like going from ferry boats and then scooting along in a sailboat. The absence of noise is remarkable. It’s at least 10dBA quieter than a similar sized petrol engined BMW at 60km/h and probably even more on a full-throttle burst.

And it's a lot faster than you might think. BMW says it can hit 100km/h in 7.2 seconds, and that's precisely how quick it feels, but it's even stronger on a rolling start.

Lithium-ion battery
The Lithium-Ion battery pack as 22kW/hrs of juice in it and discharges at 360 volts into a 125kW electric motor. But the thing is the torque. At 250Nm, it's more torque than the Mini Cooper S offers, but you don't have to wait for it to hit a peak in the rev range because it's there any time you touch the pedal.

So it leaps to 60km/h in 3.8 seconds, it does the overtaking burst from 80-120km/h in 5.4 seconds and BMW has effectively limited it to 150km/h. By then, the engine is spinning at nearly 11,000rpm, with the single, step-down gear delivering the drive to the wheels.

And it has other tricks – the Comfort overall setting delivers the fastest speed and the most comfortable environment, the EcoPro setting turns down the air conditioner and softens the throttle pedal, and the EcoPro+ mode that does both of those things more enthusiastically.

The result is that it will do between 130km and 160km on a full charge in the Comfort mode, somewhere towards 200km in the EcoPro mode and a claimed 300km in the EcoPro+ mode. On the official EU numbers, the range is claimed at 190km/h.

Within six months, though, BMW will fit a range-extending hybrid into the i3, nestling a two-cylinder, 25kW scooter engine alongside the electric motor. The petrol engine doesn’t drive the wheels but adds energy via cranking the same i3 generator that helps to recharge the battery on long descents or under braking.

The beauty of the i3 is that it’s so demonstrably easy to drive. And park. Designed for mega cities, it’s a touch less than four metres long and it can turn a full circle in 9.86m (32ft).

It helps that it’s rear drive with 50:50 weight distribution, but the i3 feels entertaining (even around our limited test track with its slaloms, chicanes and fast corners) and it punches hard any time you want it to.

The only issue with the powertrain, really, is that it sometimes develops a fluttery whine when you ask it for full acceleration, especially if there is still some steering lock on exiting a corner.

This is the sort of car that electric owners will be impressed with. It’s probably as good as any of the limited range of electric cars out there, at less cost. Current Prius owners will find the range limitations a bit too restrictive as their parallel hybrid systems carried them further than either the i3’s electric or series hybrid layouts.

There is a place in the world for a car like this and BMW hopes (no, really hopes) that it’s a growing place. Measure your lifestyle honestly first and you might find yourself loving it. But to buy it on a whim expecting it to be a standard family style machine is doing it a disservice.

What impressed . . .

Lovely seats, interesting trims, strong, quiet performance, stable road feel

. . . and what didn't

Costing the same as a 5-Series with no idea about residual values , range anxiety, tiny luggage capacity