2015 Mercedes-Benz S500 Plug-in Hybrid review

The Mercedes-Benz S500 Plug-in Hybrid offers something for nothing – in theory. 

As well as being the latest addition to the S-class range, it looks like a bit of a no-brainer for the chauffeurs and fleet drivers that make up the majority of the car’s customer base.

The list price of the car may be £90k, but with this car saving your typical 40 per cent BIK-rated company car driver just over £300 per month compared with the S300 Bluetec Hybrid, the S500 Plug-in Hybrid works out level on price with the cheapest-to-run diesel on a monthly basis – and quite a lot cheaper if you happen to live in London and regularly pay the congestion charge.

It’s powered by a 328bhp twin-turbo 3.0-litre V6 petrol engine working in tandem with a 114bhp electric motor. The former may come as a disappointment to Merc’s traditional customer if they’re expecting the S500 badge to grace a V8-powered limousine as it always has before.

But they won’t have much to moan about when they learn of the S500’s vitals. The 443bhp combined output is as much power as any non-AMG-branded V8 might provide, while the hybrid system’s 479lb ft of torque – available from just 1600rpm – is considerably greater.

The new S500 has an 8.7kWh lithium ion battery that can be charged via a seven-pin Mennekes-style cable or from a three-pin domestic outlet, the latter taking five hours from flat. It weighs 180kg more than the Bluetec Hybrid, but it’s still 2.6sec faster to accelerate from rest to 62mph, and it has an electric-only range of 18 miles.

The market is filling up with plug-in hybrids that make a lot of sense on paper but whose appeal slowly erodes as you become familiar with their real-world capabilities. The S500 is not one of those cars. It’s as driveable and easy to use as any S-class in the range, but more refined and impressively frugal within its comfort zone.

Once the battery’s flat, in normal mixed-road commuter use, it’ll return around 30-to-the-gallon. Most owners are expected to tackle shorter trips and a greater proportion of city roads than that usage pattern contains, and our test route suggests that doing so could add 50 percent to that real-world return.

The car’s four drive modes allow it to juggle electric and petrol power in ‘hybrid’ mode, to run exclusively on battery power, to maintain the current battery charge level in ‘Save’ mode, or to return the battery to full charge via the combustion engine in ‘Charge’.

The controls are light and undemanding, just as they are in any S-class – designed to be easy to modulate for unerringly smooth progress. The inconsistent pedal response of Mercedes’ lesser hybrids would never do for an S-class, but this one doesn’t suffer with it. There’s pleasing progressiveness to the initial brake pedal travel, and while you can just about hear the petrol engine starting and stopping as you vary your accelerator inputs, the engine response is always predictable.

Having almost 500lb ft available so far below 2000rpm makes a telling contribution to flexibility. You can make supremely laid-back progress in this car without dawdling or holding anyone up, simply because all that torque allows you to slip away from standing so effortlessly.