Plug-in Hybrids, or more accurately, plug-in hybrid electric vehicles (PHEV) are essentially more similar to conventional hybrids that use both a petrol or diesel engine along with an electric motor with a battery. The only difference in a plug-in hybrid is that you can charge the car's electric motor and battery by plugging it into a regular 120V outlet. The cars usually come with a rechargeable battery pack or another energy storage device, which can be recharged by plugging it into an external source of electric power.
How such car ideally functions is, the vehicle starts off in all-electric mode and then runs on battery juice until the battery fully drained out - that's usually for up to 50 or even 100 km, depending on the size of the battery. Once the battery is drained, it's the petrol or diesel-powered engine that takes over and the car functions as an ordinary, conventional hybrid. There are certain models that switch to gas mode on the go once the car reaches highway cruising speed of 80-100 kmph.
Because the initial running of the car is entirely on electric charge, there is no tailpipe pollution. In addition to that, thanks to the electric motor and battery the engine becomes a lot more fuel efficient.
Moreover, the electric motor and battery helps PHEVs produce less pollution than conventional cars, even when in hybrid mode. Idle-off turns the engine off while idling at stoplights or in traffic, thus saving fuel. Regenerative braking converts some of the energy lost during braking into usable electricity, stored in the batteries.
Plug-in hybrids have been embraced across the world and in fact in 2015 itself global sales of plug-in hybrid vehicles closed in on the 6 lakh mark. In fact the US is the largest consumer of plug-in hybrid vehicles followed by China and Japan. India too has been introduced to these vehicles but it's the infrastructure that is the need of the hour and though the Indian Government has already introduced the FAME initiative that provides incentives on such vehicles, more needs to be done.
