A self-charging hybrid combines an electric motor with a petrol or diesel engine. The conventional engine charges the battery, meaning the car can run for (very) short distances under electric power alone. As well as the engine, there are also other ways hybrids can recuperate energy for the battery - through regenerative braking, for example. The disadvantage of hybrid cars is they're usually more expensive to buy than petrols and diesels, and they're not particularly suited to high-mileage motorway driving. They're more environmentally-friendly around town, however.

A plug-in hybrid (also known as a PHEV) has a much bigger battery. This needs to be charged externally - using a dedicated electric car charger installed at home, for example. PHEVs have increasingly longer electric ranges, with some models now able to cover around 40 miles under electric power alone. The advantage of this is that, if you can charge at home and most of your journeys are relatively short, you might find that you can cover most journeys under electric power without using any fuel. Of course, the petrol or diesel engine is still there if you do need to cover the occasional longer journey. The disadvantage is, once the battery's flat, the car is lugging around a lot of unnecessary weight and will be thirstier than a normal petrol or diesel model.