Ferrari HY-KERS news - Geneva show: Ferrari HY-KERS - 2010

One horsepower per kilo is the Ferrari hybrid rule. This 599 HY-KERS hybrid has the rule applied. In other words, whatever any hybrid system costs in weight is offset by a corresponding power upgrade. Whew, so it won't be slow, then. Good.

It's mildly surprising that this car exists, but Ferrari is no different to other car manufacturers in that it has to be Seen To Be Doing Something in environmental terms, despite the fact that such a small-volume manufacturer contributes relatively little to global warming. In fact, you could argue that The Car in general contributes little, but we'll leave that alone for now. Ferrari has to play the game.

It's green. That's obvious. It's also fast. But most of all, this 599 is impressive technically. In fact, my impression of Ferrari as a company has been boosted by the fact that this machine exists. One of Ferrari's chief engineers told me that if they were to put it on sale today, the hybrid system would double the standard 599's price. Cutting edge, in other words - because Ferrari's demands for the tech are demanding indeed. It won't be on sale for at least another five years.

Batteries are skinny (20mm thick) and highly efficient lithium-ion jobs lying flat on the undertray. The motor is neatly integrated with the dual-clutch transmission at the back of the car. It is controlled by a neat electronics module located beneath the boot floor - not an inch of boot space has been lost, though. In fact there's more, because the standard 12-volt battery has been taken out of the boot and its function replaced by the module.

The hybrid 599 has regenerative braking and stop-start, and the net result is a 36 percent improvement in fuel consumption (and roughly the same in emissions) over the standard V12. And an 80kg weight gain is neatly offset by an 80bhp upgrade in power via that electric motor. There are other clever things going on too, like using said motor to fill torque holes in the V12's power delivery. They're really thinking about how this can work for a Ferrari.

Shame the F1-transfer of KERS regeneration tech is now a dead duck, because none of the F1 teams are using KERS this year. And when I asked an engineer about whether he'll ever work on an all-electric Ferrari, he said politely ‘I'd prefer not to think about it'.

Bill Thomas, Associate Editor of Top Gear magazine

See what else is being revealed in Geneva