All hybrid cars have one thing in common, they combine an internal combustion engine -- i.e., one that is powered by petrol or diesel -- with an electric motor that draws its power from a battery. However, that's where the similarities end. Understanding the differences between the types of hybrid technology available should help you make the right choice if you're considering selecting something greener as the next family runaround.
Putting pollution first: Series Hybrid
Also often referred to as an extended-range electric vehicle, cars that use this form of hybrid technology such as the Chevrolet Volt (pictured) and Opel Ampera only ever use an electric motor to power the wheels. There's a petrol engine too, but that only fires up to charge the batteries when they're running out of juice. The idea is that if you use the car primarily for short daily commutes or trips into a city, the car is a zero-emissions electric vehicle. Just plug it back into a power socket on the return home and the battery's ready again the next morning. However, for longer journeys, rather than having to stop and recharge every 30 miles (50 km) or so, a small petrol-powered engine kicks in and works like a power generator, charging up the batteries and multiplying the car's range by a factor of 10. As a rule, Series Hybrids tend to be more expensive than other forms of hybrid due to the size and complex nature of their batteries.
Like a normal car with better fuel economy: Parallel Hybrid
The most common form of hybrid thanks to the success of the Toyota Prius here, it can use power solely from the electric or petrol/diesel-powered engine to drive the wheels or a combination of the two engines simultaneously. Rather than use the internal combustion engine for recharging the battery, energy is recuperated via regenerative braking and coasting. The idea is that the car produces zero emissions at very low speeds when just the battery is being used, and minimizes fuel consumption at higher speeds by running the two engines simultaneously. The electric motor reducing the strain on the petrol engine so that it burns less fuel. That's the idea, but in reality, many Parallel Hybrids fail to match the fuel economy of modern diesel cars, even if they are much quieter.
Electric performance with fossil-fuel range: Plug-in Hybrid
As the name suggests, the battery portion of the car's powerplant needs to be connected to a charging station or a mains power outlet to charge up, and the car will be capable of traveling solely on the electrical energy from the battery. However, it can be either a Series or Parallel Hybrid. The most phenomenal example of this category is the Volkswagen XL1. It is capable of travelling 300 miles on a single gallon of diesel (100km on 1 liter), thanks to the combination of electric motor support, an incredibly streamlined shape and the use of the strongest, lightest construction materials available. However, that efficiency comes at a price of over €120,000 and production is limited to 250 examples, none of which will be sold outside of Europe.
For no-smoking zones: Mild Hybrid
Better known as Stop/Go or Stop/Start technology, the majority of new petrol-powered cars come with this form of hybrid technology as standard - even the latest Lamborghini. It cuts the car's engine when it is at a standstill and in neutral. When the accelerator is depressed, the engine automatically fires up again. Regenerative braking keeps the battery-powered system charged without draining fuel from the engine. So no tailpipe smoke at traffic junctions or in heavy congestion, keeping the air cleaner and reducing fuel waste.