BMW is plugging into the electrified future of automobiles by offering a plug-in variant across its product line. The 740e full-size sedan benefits from the same lightweight carbon core construction and impressive list of technology features as the redesigned luxury flagship, but it has a 2.0-liter gasoline engine along with an electric motor powered by a lithium ion battery pack.

Plug-in hybrids differ from traditional hybrids such as the Toyota Prius, which charges its batteries mainly from regenerative braking. The main source of propulsion comes from the gas engine. Plug-in hybrids can be plugged into a 110-volt wall outlet or a 240-volt Level 2 charging station to boost electric power for gas-free driving. In the case of the 740e that amounts to around 13 miles.

Thirteen miles may not sound like much, but there are various scenarios to take advantage of the plug-in hybrid model. Lower speed driving around town can be achieved with electric power only in MAX eDrive mode.

The car can drive at highway speeds purely on electric power, but the battery depletes faster. Switching to “Battery Control” mode, the engine will recharge the battery while driving so that once you get off the highway, which is where gas engines are most efficient, the electric-only miles kick in around town, where hybrids are most efficient. In default Auto eDrive mode, the vehicle automatically cycles between gas and battery power.

A week of mostly city driving yielded 31.9 mpg actual. That is impressive for a luxury car of this size. Its gas-only sibling, 740i xDrive, is rated at 19 mpg city, 28 mpg highway. There are no compromises in the performance department, as the two versions have equal acceleration numbers. Since the electric motor is incorporated into an eight-speed transmission, the driving experience feels mostly conventional; it's extra quiet when running off battery-only power, and regenerative braking slows the car with less pedal effort.

A plug-in hybrid works well for people who might do a lot of gas-free shorter and/or lower speed trips. But you need a place to plug it in.

It raises the inevitable question of who will buy this car, which is about $4,600 more than the gas model. Someone shopping at the $100,000 price point is not likely to be too concerned about gas prices. That doesn't mean you have to hate the earth, either. Even Montgomery Burns would appreciate the fact that you would be buying electricity from an outside source to charge it.

The techie appeal of the 740e's electric drive — switching between modes to try to optimize mileage — is pretty neat. As cars seem to be evolving to desensitize drivers, it's about the most engaging thing you can drive short of a manual transmission.

Andy Mikonis is a freelance writer.