I’ve been driving around in an Audi A3 Sportback for the last week. It has been, in general, a largely unremarkable seven days. And I say unremarkable in the sense that the Audi handles pretty much as an Audi should, that the build quality is everything you’d expect and the cabin remains a wonderfully civil place to be.

Looks, however, can be deceiving because this is no ordinary Audi. Drumroll please. This, ladies and gentleman, is the Audi A3 Sportback e-tron.

What that means to you and me is an astounding 188.3mpg and a congestion-charge exempt CO2 emissions rating of 37g/km. The question is, how do they do it?

The A3 e-tron is Audi’s first hybrid. It pairs a 150hp 1.4TFSi combustion engine with a 100hp electric motor. The result is - and yes I know that these figures don’t add up - a 204hp environmentally-friendly reasonably hot hatchback capable of hitting 62mph in just 7.6 seconds.

It’s a remarkable achievement, and I’ll get to the science behind it later, but owners will have to make a small sacrifice. About 100 litres, in fact, because that’s how much luggage-carrying capacity is swallowed up by the battery pack under the rear seats. The charging cables are stored in a case in, you guessed it, the boot, so you might find that the weekend bag is the only option if you don’t want to leave them at home.

What you do get, however, is a proper Audi. Externally only e-tron badges on the boot and wings give anything away otherwise the clean lines of the standard A3 Sportback remain unchanged. The charging socket is cleverly secreted away behind the four rings of the Audi badge on the grille, accessed by twisting a small latch and then sliding the insignia to one side.

Turn on the ignition, such as it is, and you’re greeted with... absolute silence. There are four modes to choose from – EV, Hybrid, Hold and Charge – accessed via a toggle switch on the dash but, whichever one you select, you’ll always pull away on battery power alone. Should you decide to continue that way you’ll enjoy a maximum range of 31 miles at up to 80mph although, naturally, high speeds will impact on how far you can travel.

Depending on your power source, topping up the e-tron’s batteries can take between two hours and 15 minutes at a charging station and three hours 45 minutes using a domestic supply. However, as I don’t have either a driveway, or a garage, charging the e-tron overnight – the ideal time – is simply impractical.

Fortunately you can top up the batteries using the combustion engine but, as a result, fuel economy takes a massive hit and that 188.3mpg drops to below 30. An energy recovery system, similar to the systems used is Formula One cars, will charge the battery under braking or while coasting.

Hold mode preserves battery power until you arrive in a built-up area, where you might prefer to use the electric motor while Hybrid aims to make best use of the combined energy available from the batteries and combustion engine. However, unless you’ve got a delicate right foot there’s a decidedly uncomfortable thump as the engine fires up.

All the power is channelled through a six-speed DSG gearbox, which includes an additional clutch to allow coasting which is a more efficient use of kinetic energy than recuperation. There are wheel-mounted paddles to let you change gear manually, if you prefer, but they’re tiny, and using them is a bit like tugging on someone’s ears.

The transition between power sources on the move is indiscernible with the engine inaudible under normal loads. In fact, progress is serene thanks to an absorbent ride and sweet handling, helped in no small part by the improved weight distribution – 55:45 – compared to the diesel’s 60:40.

There’s a lot of science and technology behind the scenes making the A3 e-tron work but, as complicated as it all sounds, for you and me it’s all very straightforward. So is deciding whether or not you should think about buying one. If your commute is within its 31-mile electric range then it’ll save you money but only if you can charge it every night which, if you don’t have a driveway or garage, could be impractical, or if you have access to a charging point which, let’s be honest, most of us don’t. It’s expensive, too, at more than £34,000 so, while there are definite savings to be made, not everyone will be in a position to make them.

Congestion-charge evading emissions of just 37g/km (or 39g/km if you select the optional 18in wheels) obviously make a stronger case for buying this car so if you happen to be one of the lucky ones you’ll snare yourself one of the most entertaining models in the A3 range and, potentially, one of the cheapest to run. If you can realise that potential, you’re onto a winner.

Audi A3 Sportback e-tron

PRICE: £34,305*

AS TESTED: £39,455

ENGINE: 1.4-litre TFSI

BATTERY: 8.8 kwh

TRANSMISSION: 6-speed DSG S TRONIC

POWER: 204bhp

MAXIMUM SPEED: 137mph (hybrid mode)

80mph (electric mode)

ACCELERATION (0-62mph): 7.6sec (hybrid mode)

(0-37mph): 4.9sec (electric mode)

ECONOMY: 188.3mpg

CO2 EMISSIONS (AS TESTED): 39g/km

*Excludes government plug-in car grant.

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