If somebody had told you a decade ago that they drove a hybrid car, you could have been reasonably confident they were the owner of a Toyota Prius. Ten years later you can make no such assumption. For one thing there are now so many hybrid cars on sale from manufacturers far and wide that the Prius plays only a small role in what has become a major production. Perhaps more pertinently still there are now several different types of hybrid powertrain, each one of them suited to slightly different motoring tasks.
For the typical new car buyer it can be completely overwhelming. There are mild hybrids and conventional hybrids, plug-in hybrids and range extender hybrids. It is also no longer the case that hybrid cars are simply about efficiency and low running costs. Today, some of the fastest cars on the road have hybrid powertrains.
This guide will explain exactly what a hybrid car is before looking at the various types of hybrid powertrain, as well as offering examples of each.
What is a hybrid car?
In very simple terms a hybrid car is one that uses both an electric motor and a petrol or diesel engine to generate drive in order to improve fuel efficiency and reduce tailpipe emissions.
Depending on the type of hybrid in question the motor and engine may work together in parallel, one after the other in series, or in some combination of the two. The car’s onboard computer will seamlessly juggle the motor and engine depending on driving conditions, but the driver can often choose to disable the combustion engine, at least until the battery is depleted.
Increasingly, hybrid powertrains are being used in performance cars to achieve ever greater acceleration times, but more often than not a hybrid system is there to reduce running costs and harmful emissions.
By using less fuel than conventional petrol or diesel vehicles, hybrids can be cheaper to run, but they are also more tax efficient for company car drivers and they may be may be exempt from the London congestion charge, too. They use technologies such as stop-start, which reduces fuel consumption in traffic, and regenerative braking, which captures energy that would normally be lost when slowing down in order to help recharge the batteries.
Range extender hybrid
On a range extender hybrid the combustion engine is not physically connected to the wheels. It isn’t there to provide drive. Only the electric motor turns the wheels. The engine’s one role is to produce electrical energy to charge the batteries, like a generator. For that reason a range extender hybrid is really just a battery-electric car, but with its own on-board generator.
The advantage is that a range extender car has a greater range than a pure EV car, making it more flexible and useable over longer distances. However, the generator cannot recharge the batteries indefinitely and its small fuel tank will eventually run dry. In the case of the BMW i3, the range extender hybrid system increases the car’s range to 206 miles, whereas the electric-only i3 can manage just 125 miles.
The main disadvantage of a range extender, apart from the increased cost, is that the car is no longer a zero emissions vehicle. A range extender hybrid is appropriate for somebody who mostly drives short distances in town and occasionally slightly longer distances, without ever embarking on very long journeys. It is important to plug-in regularly to a mains power source to charge the batteries, just like a pure EV.
Example: BMW i3 - £36,490
A mild hybrid uses an electric motor to augment the petrol or diesel engine. The hybrid system is simply there to play a supporting role - it isn’t substantial enough to drive the car along on its own. There is no means of plugging the car into a mains power source to recharge the battery.
The point of a mild hybrid system is - by way of example - to combine the performance of a 3-litre, six-cylinder combustion engine with the efficiency of a 2-litre, four-cylinder engine. Like other types of hybrid powertrain, mild hybrids use regenerative braking to harvest energy when slowing down to recharge the small battery. They’re best suited to drivers who cover longer distances on a regular basis, but want better fuel economy than can be achieved by a conventional combustion engine vehicle.
Example: Audi SQ7 - £74,385
This is the original type of hybrid car, the sort that was most common a decade ago. Its hybrid system is substantial enough to drive the car along on its own, but only over very short distances - probably no more than a mile. At very low speeds it will power the car independently of the combustion engine, whose role it is to drive the car along at medium and high speeds, as well as during hard acceleration. The motor and engine can work together in parallel, or independently of one another.
In a busy city a hybrid car’s fuel consumption and harmful emissions are far better than that of a conventional petrol or diesel model, but it has the same range and flexibility. Hybrid cars are popular with taxi and private hire firms because they’re cheaper to run than a typical combustion engine car. There is no way of plugging a hybrid car into the mains to charge the batteries. Instead, this is done partly by the engine, which can work as a generator, and through regenerative braking.
Example: Lexus IS 300h - £32,895
A sort of halfway house between full hybrid cars and pure EVs, plug-in hybrids are becoming increasingly prevalent. They have much greater battery capacity than conventional hybrids, which means they can cover 20 or 30 miles, and sometimes more, on electric power alone. For longer journeys the petrol or diesel engine and full-size fuel tank give them much the same range and usability as a combustion engine car. The engine and motor can work together, or independently of one another.
As suggested by the name they can be plugged in to a mains power source to recharge the battery, although this can also be done through the engine operating as a generator and regenerative braking. In fact, it’s important to be able to charge the car regularly at home, at work or at a public charging point in order to make use of the car’s hybrid capability. For drivers who cannot charge regularly, a conventional petrol or diesel car will actually be more efficient in the long run. Those who can charge regularly will find that many of their journeys can be completed on electric power alone, for next to no cost.
Examples: VW Golf GTE - £31,100
A sports car or supercar may use a hybrid system to improve efficiency and give it a short electric-only range, but its main job is to enhance the car’s performance. A performance hybrid will use at least one electric motor to augment the combustion engine’s power output, making the car faster. Very often it will be used to drive the front axle where the engine powers the rear axle, technically making the car four-wheel drive and therefore giving it sharper acceleration away from a corner.
It will use regenerative braking and the combustion engine to charge its batteries, and it may or may not have plug-in capability. When it does, as in the case of the BMW i8, the car will have a much greater electric-only range.
Example: Honda NSX - £143,020