Audi is in the midst of preparing a plug-in hybrid version of its flagship Q8 SUV, and a prototype unit has been spotted doing winter tests by our spy photographers. If you look closely, there’s a new charging port on the rear left fender, along with rounded yellow stickers around the vehicle that indicate it’s a hybrid test unit.

Now, it’s unclear what exactly lurks underneath the surface, but the Q8 PHEV could be offered in 55 TFSI e or 60 TFSI e guises. The electrified powertrains were detailed at the recently concluded Geneva show – the 55 TFSI e is powered by a 3.0 litre petrol-hybrid V6 with a total system output of 363 hp and 500 Nm, whereas the 60 TFSI e makes a whopping 443 hp and 699 Nm of torque.

The entry-level 50 TFSI e, on the other hand, is powered by a 2.0 litre four-cylinder petrol-hybrid engine with a total system output of 295 hp and 450 Nm. All three electrified powertrains come with all-wheel drive/four-wheel drive as standard, although 50 TFSI e models are able to decouple the rear wheels from the drivetrain, effectively reducing mechanical drag for better efficiency.

As with the rest of the plug-in hybrid Audis, the Q8 looks set to share the same 14.1 kWh lithium-ion battery, which should deliver a pure electric range of over 40 km (based on WLTP standards). The brake regeneration system – derived from the Audi e-tron – is able to recover up to 80 kW, and a full charge via cable and a 7.2-kW charger will take about two hours. Expect the Q8 PHEV to debut sometime this year.