MPH: Mark Hughes on...

"If a non-KERS car wins at Monza I'll be seriously impressed," said Jenson Button, some time before the recent flurry of victories for KERS machines. The length of that pit straight and the fact that you can use the boost button once before the start/finish line and again after it, means KERS contributes much more to lap time than at more conventional tracks.

But even at those other circuits the technology has been making for some fascinating dilemmas - both on and off the track - even if it has introduced a horrendous cost to the sport at the most inappropriate time imaginable.

On-track, how do you go about racing them? Now that McLaren and Ferrari have begun fielding genuinely quick KERS cars, their rivals have found their strategic options horribly complex. They had the fastest cars over a lap but even had they qualified on pole, they were still almost certain to be passed off the grid - or later on the first lap - by the leading KERS cars.

The KERS boost was making them much the more raceable cars, so long as they were somewhere close in qualifying.

At Valencia, Brawn opted to surrender grid position to the McLarens in favour of race strategy, with longer stops to leapfrog them past. It worked. The situation for Red Bull at Spa was similar, but complicated further by a quick Force India, Toyota and BMW.

Using the Valencia Brawn strategy and fuelling heavier than the Ferrari would potentially put you not just behind it on the grid, but behind the other quick cars too - as Red Bull found to its cost. No matter how long your first stint, the prospect of leapfrogging seven cars would be slim, almost as slim as the prospects of overtaking the KERS cars on-track because they would be faster than you at precisely the places where passing is possible.

The Red Bulls were almost 1s quicker in the high-downforce demands of sector two at Spa but there are no passing places there, so the Ferrari could pass in sector one, hold them up all the way through their good bit, then pull away again.

Off-track, the pact between the FOTA teams not to use KERS next year could be broken if Williams refuses to be party to the pact. If it is running it next year, pretty much everyone is obliged to and the on-track interest created by a mix of KERS and non-KERS cars that are faster and slower at different points of the track dissolves, but everyone still has to spend the money to neutralise the threat. But the technical fascination will remain.

Mercedes engines director Andy Cowell talked us through the best of the current systems, as used in the McLaren. It comprises the motor generator (effectively an alternator), a power electronics unit that converts the three-phase electrical energy to direct current and finally the battery, which converts that energy into chemical form and stores it.

The motor generator sits on the end of the crankshaft, the power electronics unit at the back of the right-hand sidepod, the battery on the left. The package weighs 25kg, the battery comprising 14.5kg of that. Giving some idea of how fast the technology has progressed, the prototype weighed over 100kg and the first unit fitted to a test car 37kg.

The process of converting mechanical energy from the wheels to electric to chemical, then all the way back again when the KERS button is used inevitably creates energy losses. This is measured as a 'round trip' efficiency and in its initial form it was just 30 per cent. In other words, 70 per cent of the energy was lost. Now 70 per cent of the energy is retained and only 30 per cent lost.

Analogous to how the energy heads first in one direction then the other, Cowell makes the point that in the initial development of KERS his team was receiving much of the information from its road car counterparts, but now that flow is going in the other direction.