Plug-in Hybrid Electric Vehicle

A plug-in hybrid electric vehicle, universally shortened to PHEV, is a car that carries both a conventional combustion engine and an electric motor fed by a battery large enough to be recharged from the mains and to drive the car on electricity alone for a meaningful distance. It occupies the middle ground between the ordinary hybrid, whose small battery only ever assists the engine, and the fully electric car, which has no engine at all. The defining trait is in the name: unlike a self-charging hybrid, a PHEV has a charging socket, and that ability to draw energy from the grid is what gives it a genuine electric-only range.

That usable range typically falls somewhere between 40 and 100 kilometres on a full charge, which is enough to cover most people's daily commuting and errands without burning any fuel. For shorter trips the car behaves like a quiet, smooth electric vehicle, drawing on a battery that is far larger than a hybrid's, often in the region of 10 to 25 kilowatt-hours. When the battery is depleted, or when the driver demands more performance than the motor can supply, the combustion engine steps in, and the vehicle continues to function as an efficient conventional hybrid with the long range and quick refuelling of petrol or diesel. This dual nature is the PHEV's central appeal: electric motoring for the everyday, liquid fuel for the occasional long journey, and no dependence on finding a charger en route.

The efficiency of a PHEV is uniquely dependent on how its owner uses it. Driven sensibly by someone who plugs in regularly and keeps most journeys within the electric range, it can achieve very low running costs and tailpipe emissions, in effect operating as an electric car most of the time. Driven by someone who never charges it, the same vehicle becomes a heavy car hauling around a large battery and an engine, and its real-world fuel consumption can be worse than that of an equivalent conventional model. This behaviour-dependence is why official PHEV economy figures, measured on a fully charged battery, often look far better than the averages drivers actually record.

The technology has been a pragmatic stepping stone in the transition away from fossil fuels, offering buyers a way to electrify part of their driving without the range anxiety that deters some from going fully electric, and giving manufacturers a route to lower fleet-average emissions. Several powertrain layouts exist, from systems where the engine and motor can each drive the wheels, to series-style arrangements where the engine mainly acts as a generator.

In the broader family of electrified cars the PHEV sits a clear step above the mild hybrid and the full hybrid, both of which cannot be plugged in, and a step below the battery electric vehicle, which dispenses with the engine entirely. Its value rests largely on the driver's discipline in keeping the battery charged, which is why the concept of electric range is so central to understanding what a plug-in hybrid can and cannot deliver.