There are a few particular stats concerning the new Mercedes S500 Plug-in Hybrid that grab your attention when skimming the spec sheet. Namely, combined fuel consumption of 100.9mpg, CO2 emissions of 65g/km and 0-62mph in 5.2 seconds.
They’re not a misprint – this is the greenest S-class yet, with a 3.0-litre petrol-fuelled V6 joined by a 114bhp electric motor taking its energy from a big lithium-ion battery pack in the boot. It’s also the first of a raft of new plug-in Mercs, with 10 further hybrids planned by 2017.
Hold on. Aren’t there hybrid versions of the Mercedes S-class already?
Yes, the petrol-electric S400 and the diesel-electric S300 BlueTec. In their case, though, the electric motor’s job is more to take the edge off the combustion engine’s consumption and augment its performance than provide much in the way of meaningful zero-emissions mileage.
The S500 Plug-in Hybrid can manage far more than a bit of low-speed gliding around car parks. A much bigger battery pack (and the ability to plug it into the mains or a faster wallbox charger to pre-charge it) means it can manage up to 20 miles on electric power alone before the petrol engine kicks in. That said, on our initial 11-mile drive at low speeds through city streets the V6 whirred into life just around the corner from our destination.
Charging takes around two hours at a wallbox or between two hours 45 minutes and four hours through the mains, via a socket in the rear bumper.
What’s the Mercedes S500 Plug-in like to drive?
Just as imperious as the non-hybrid limo models, but with the added serenity of near-silence when running in electric mode.
There are occasionally a few more noticeable clunks and shunts from the seven-speed transmission than you might ideally like but otherwise this is as refined as luxury travel gets. Adaptive air suspension ensures ride quality is suitably smooth and when you touch the brake pedal the system does a decent job of overlapping the mechanical brakes and electric motor deceleration unobtrusively.
For what it’s worth, this car is jolly fast too: when both the electric motor and the V6 put their heads together there’s a total of 436bhp and enough performance for enthusiastic chauffeurs to pin their passengers far into the S-class’s cushioned head rests.
There are four driving modes to choose from: E-mode (electric power only), E-save (uses as little battery power as possible), Charge (charges the battery as you drive) and Hybrid (the default mode, which does a little of everything).
Mercedes S500 Plug-in technology highlights
Being an S-Class, it’s rammed with clever and complicated tech. A party piece Mercedes seems particularly proud of is the car’s ability to turn the local topography to its advantage; for example, if you’ve programmed a hilly route into the sat-nav the S500 will use the electric motor to help the car uphill and flatten the battery as much as possible so it can recharge on the way down. Equally, the system will make sure you get to urban areas with as much charge as possible so you can make the most of the electric motor.
There’s also a ‘haptic accelerator pedal’. If you’ve set the transmission to Economy+ mode, on downhill stretches or when following traffic a series of pulses through the throttle pedal tells you that you should really take your foot off the gas to allow the drivetrain to coast or regenerate energy. That’s right, the hybrid S-Class is sentient to the point where it will essentially chide you for tailgating.
You can also set the interior temperature before you climb in via your smartphone, which can be linked to the climate control and heated seats, steering wheel and armrest. The app will even tell you how much charge is left in the battery from the comfort of your front room.
A sizeable chunk of boot space is lost to a doorstep-shaped ledge that covers the big battery pack and the plug-in S-class is available in long-wheelbase form only - but it’s otherwise identical to any other model in the range. It does carry a more heavyweight price tag though, at around £17,000 more than an S350 BlueTec diesel.
The jury’s out on the exact extent you’d be saving the planet by choosing the plug-in. That spec sheet-dominating 65g/km CO2 figure owes a little to the rather generous way hybrids’ emissions are calculated by the EU (the electric-only range is carried wholesale into the calculations), since the engine generates 149g/km of CO2.
On a separate note, the twin-screen S-Class dashboard is beginning to look a little dated already – maybe Merc has a more elegant instrument panel in the pipeline for when facelift time rolls around.
You’d hesitate to call it ‘green’ wholeheartedly, but the Mercedes-Benz S500 Plug-in’s efficiency figures are undeniably impressive. For buyers with largely city-based driving habits and access to charging infrastructure, it’s arguably the pick of the range.
Most buyers will forgo the faffing with power cables and plump for the more affordable S350 diesel, though. The S500 Plug-in is expected to make up around 3-5% of S-class sales in the UK.