Green motoring comes at a hefty price with the Mercedes-Benz S 500 Plug-in Hybrd but that's the only sticking point, says motoring editor Andy Russell.

As the hybrid market gains pace, these growing green cars don't come much pacier than the new Mercedes-Benx S 500 Plug-in Hybrid.

The third hybrid in this luxury saloon range, this is the first plug-in and can be topped up in around two hours via a fast charging point that plugs into a port in the back bumper.

Combining a 3.0-litre V6 biturbo petrol engine and a powerful electric motor, for a total 449hp and the ability to travel more than 20 miles purely on electric power, gives performance figures as mightily impressive as the S-Class itself – 0 to 62mph in just over five seconds and a top speed limited to 155mph while capable of more than 100mpg combined with CO2 emissions of just 65g/km so the S 500 Plug-in Hybrid is exempt from road tax and London Congestion Charge while, if lucky enough to have one as a company car, you pay benefit-in-kind tax on only five per cent of its value – that's not a lot even with the £87,965 price tag.

The S-Class is one of the world's most luxurious, desirable saloons and the new ultra-refined power system, with seven-speed automatic transmission, makes it even better.

In electric mode, capable of propelling this 2.2-tonne car at up to 87mph, you are aware only of the swish of tyres on the road and you hardly notice the petrol engine so motorway cruising is near silent.

While 100mpg is unlikely in real-world driving, with care and clever built-in technology, which looks at the route to predict where energy can be harvested when coasting and braking to top up the battery, you can achieve economy figures on a par with superminis.

It's even more extraordinary given this executive express's blistering sports car-like performance regardless of power supply.

Four modes match the power supply to driving conditions:

Hybrid – uses the petrol engine with the electric motor.

E-Mode – electric power alone.

E-Save – holds battery charge for use in stop-start traffic.

Charge – petrol engine generates electricity and quickly tops up the battery while driving.

While you get all the comfort, luxurious ride and cabin space of the S-Class, the battery pack eats into space at the back of the boot, reducing it to a still useful 395 litres.

The S 500 Plug-in Hybrid is out of most people's price range but its technology highlights how far hybrid power has come and, very importantly, this know-how will filter down into more affordable forthcoming future models.