Electric vehicles explained

There seems little doubt that electric cars will play an increasing role throughout the next decade, particularly for short-journey city dwellers, but there's more than one type. Here are the main options.

Hybrid
An electric motor assists a petrol (or, in future, diesel) engine, so that engine doesn't have to be as big or as powerful as if it was working unaided. Hybrids hardly ever drive on electric power alone. Batteries are recharged by the engine, or regenerative braking.

Plug-in hybrid
Capable of being driven for more of the time as a pure electric car, but still primarily relies on an internal combustion engine. These cars can be recharged from the mains, or on the move, as with a non-plug-in hybrid.

EV
Electric vehicle plug it in to a power socket, charge it, drive it until the batteries are almost flat, then repeat the process. This is predominantly a solution for short commuter driving.

EREV
Extended range electric vehicle. Always runs on electricity, and is recharged from the mains, but has an alternative power source on board (in Ampera's case, a petrol engine) that acts as a generator to drive the electric motor once the batteries are exhausted.

Fuel cell
In a fuel cell vehicle, hydrogen reacts with oxygen to create electricity, with water as the only tailpipe emission. Great, except the fuel cells cost a fortune, there's no hydrogen refuelling infrastructure yet and the creation, transport and storage of hydrogen is energy-intensive.