What is it?
The Mercedes-Benz S 500 Plug-in Hybrid is the first of up to ten petrol- and/or diesel-electric powered models confirmed for launch by the German car maker before the end of 2017.
It succeeds the S 300 BlueTEC Hybrid and S 400 Hybrid but adds one vital new element, namely the ability of its battery to be charged via either standard household mains electricity or a high voltage electrical system – rather than simply by recuperated means or on the go via the petrol engine.
This allows the S 500 Plug-in Hybrid to use a much larger lithium ion battery than its predecessors, which in turn provides its electric motor with far greater energy reserves and, crucially, a more than ten-fold increase in electric range.
On a feathered throttle in optimal weather conditions, it is claimed to be able to travel up to 20 miles before its battery is depleted and the petrol engine is fired up.
At the heart of the hi-tech luxury saloon is a newly developed plug-in hybrid system described as boasting modular properties that will allow it to be tailored for use with varying outputs in a wide range of upcoming alternative drive Mercedes-Benz models.
In the S500 Plug-in Hybrid the new system employs a turbocharged 3.0-litre V6 direct injection petrol engine developing 242bhp and 354lb ft. The electric motor, meanwhile, is set within the forward section of the gearbox, and generates 114bhp and 251lb ft.
Together, the petrol engine and electric motor provide a combined system output of 436bhp and 479lb ft. This gives the S 500 Plug-in Hybrid greater reserves than the Porsche Panamera S E-Hybrid, whose supercharged 3.0-litre petrol engine and electric motor deliver a combined 415bhp and 435lb ft.
The combined output is channeled through a seven-speed automatic gearbox to the rear wheels in any one of the four different driving modes: Hybrid, E-mode, E-save and Charge. Additionally, the gearbox offers three separate modes: E (Efficiency), S (Sport) and E (Economy).
As an incentive to prospective buyers, Mercedes-Benz is offering a six year/60,000 mile performance guarantee for the S 500 Plug-in Hybrid’s 8.7kWh battery.
More than anything else, though, it is the battery which adds to the weight of the new car. At 2140kg, it tips the scales 145kg above the more traditional turbocharged 4.7-litre V8-powered S500.