Economical isn't exactly the first word that pops in your head when you see a large luxury sedan. We imagine them with big six-cylinder or V8 engine, nestled under their imposing front ends. But the world is a different place now, and these limousines should be greener.

BMW's solution to that is fitting batteries into their large 7 Series sedan, hooked it up to a new straight-six engine, and put a socket on its fender. Yes, behind the massive snout of the facelifted 7 Series lies a hybrid powertrain, a plug-in system to be exact. While a green full-sized sedan sounds a bit of an oxymoron for some, the plug-in hybrid version of the 7 Series promises to deliver both power and economy.

2020 BMW 745e goes green, gets up to 47 km/l image

Badged as 745e or 745Le for long-wheelbase versions, the greener 7 Series uses a boosted 3.0-liter inline-six which then makes 286 PS and 450 Nm of torque. The electric motor is then integrated into the eight-speed automatic transmission to serve as a generator to recoup energy from braking, coasting, or going downhill. Tweaks to the electric drive system means it makes more power, making 113 PS and 265 Nm of torque.

The plug-in 7 Series also has the capacity to run on pure electric power as well, capable of up to 58 kilometers with no assistance from the gas engine. As mentioned, the batteries can regain charge by means of braking, coasting, and rolling downhill. But for those who always want to have fully-charged batteries, that's where the plug-in kit comes in. The charging system can top up the 12 kWh lithium-ion battery in 4.4 hours (if fully drained) when it is charged up to a 230v socket.

2020 BMW 745e goes green, gets up to 47 km/l image

With the engine and electric motors working together, combined output is rated at 394 PS and 600 Nm of torque. As a result, the 745e can do 0 to 100 km/h in 5.2 seconds, while the longer, heavier 745Le does the same task in 5.3 seconds. All-wheel drive is available and is badged as 745Le xDrive and can do the century sprint in 5.1 seconds. As it's a plug-in hybrid, it pulls up impressive fuel economy figures too; up to a staggering 47.6 kilometers per liter for the standard wheelbase version.