The front exterior of the Volvo XC40

How do hybrid cars work?

How do hybrid cars work, what types are available and would a hybrid suit you? Find out all you need to know about hybrid cars with our handy guide.

Hybrid cars are more popular than ever and there are a huge range of high-quality used hybrid cars to choose from. Not every hybrid is the same, however, with ‘conventional hybrid’, ‘self-charging hybrid’, ‘mild hybrid’ and ‘plug-in hybrid’ all terms that you might come across. So what is a hybrid car and what are the pros and cons of them? We’re on hand to explain.

How do hybrid cars work?

Hybrid cars combine two different power sources – a conventional petrol or diesel engine and an electric motor. Their aim is to give improved fuel economy and emissions over cars powered by petrol or diesel alone.

The majority of hybrid cars use the (petrol or diesel) engine as the main power source, with the electric motor providing extra power when needed. Many hybrids can run solely on electric power for shorter distances and at low speed, with some of the most modern examples allowing many people to commute to and from work on electric power alone.

What is a conventional hybrid?

A conventional hybrid is also known as a ‘full hybrid’ or a ‘parallel hybrid’, or more recently ‘self-charging hybrid’. It was the first type of hybrid car to be mass-produced and the most well-known of this type is the Toyota Prius.

These models use an engine (usually petrol) for power, with support from an electric motor. The motor can drive the car for short periods by itself, typically a mile or so, but is mainly used to help the engine. The battery for the electric motor is charged using energy recovered by braking or by the engine so there’s no need (and no way) to plug in and charge it yourself.

What is a plug-in hybrid?

Plug-in hybrids (or PHEVs) are increasingly becoming the norm. Plug-in hybrids have a bigger battery and more powerful electric motor than conventional hybrids, which allows them to go much farther using electric power alone. Typical electric-only driving ranges vary between 20-40 miles depending on model, although some can do more than this. 

Plug-in hybrids promise much lower fuel consumption and emissions than a conventional hybrid, but you need to keep them charged to get the full benefits. A plug-in hybrid charges itself when driving (in the same way as a conventional hybrid), but the battery needs to be charged using a home, work or public charger to generate enough power for the electric motor to be used fully. It generally takes about 2-4 hours. When the battery isn’t charged, a plug-in hybrid behaves in the same way as a conventional hybrid, with the electric motor assisting the engine or driving the wheels for short periods when there’s enough charge.

Plug-in hybrids offer some of the benefits of both a petrol car and an electric car. If there’s not enough battery charge you can always use the petrol (or diesel) engine, yet the electric-only range is enough for many peoples’ daily commute. 

The best-selling plug-in hybrid is the Mitsubishi Outlander PHEV, but there are plug-in hybrids to suit most lifestyles and budgets. Volvo now offers at least one plug-in hybrid version in each model range, for example, and brands such as BMW, Mercedes-Benz and Volkswagen all offer a wide range of plug-in hybrid cars.

What is a mild hybrid?

Mild hybrids (MHEVs) are the simplest form of hybrid. They use a small electric motor that starts the car, stores energy when braking and which can assist the engine and electrical system on the move. The motor isn’t powerful enough to drive the wheels on its own, so mild hybrids give only a very small improvement in fuel economy and emissions over a conventional petrol or diesel car.

Mild hybrids provide such limited electric power that they aren’t usually classed as ‘proper’ hybrids as such. In fact, many car brands are adding this technology to their newest petrol and diesel engines to improve efficiency without labelling them as hybrid cars at all.

What benefits do hybrid cars offer?

The two main benefits of buying a hybrid car are reduced running costs and reduced environmental impact because hybrid cars often promise much lower fuel consumption and emissions than a petrol or diesel equivalent.

Plug-in hybrids offer the biggest potential benefits, with some having an official average of well over 200mpg and CO2 emissions of less than 50g/km. What you get in the real world will depend on how often you charge the battery, but if you keep it topped up many plug-in hybrids have an electric-only range of about 30 miles. In pure electric mode you travel in near-silence with zero emissions, as you do with a fully electric car (EV).

Conventional hybrids don’t offer such a long electric-only range or such low fuel consumption or emissions. They cost a lot less to buy than a plug-in hybrid though and because their batteries are always charged by the engine you get consistently good fuel economy. 

The most efficient conventional hybrids have an official average of about 90mpg. You’re unlikely to achieve this in real-world conditions but you’ll get fuel economy that’s a match for an equivalent diesel option in a car that costs much the same but produces less emissions and costs less to tax.

Mild hybrids offer slightly better mpg and emissions than a conventional petrol or diesel car, for roughly the same price. Increasingly, you won’t be able to choose a mild hybrid version of a certain model because the technology will come as standard.

Is a hybrid car right for me?

Hybrid cars are a great choice and there are so many options now that there’s a hybrid to suit most buyers’ needs.

Conventional hybrids

Conventional hybrids are a great alternative to petrol or diesel cars because you use them in exactly the same way. There’s no need to charge them and you simply fill up at the pumps. Although they tend to cost a bit more than an equivalent petrol or diesel car conventional hybrids generally give you better fuel economy and much lower emissions and tax ratings.

Plug-in hybrids

Plug-in hybrids give you all the benefits of a conventional hybrid but with even lower fuel consumption and emissions and the ability to make many journeys using electric power alone. This can make a real difference to your running costs and to your environmental impact. If you have a home or work charger that you can plug in to regularly and you generally only make short journeys, a plug-in hybrid could be perfect for you.

Plug-in hybrids do cost more than conventional hybrids though. Also, if you don’t keep them fully charged the electric motor won’t be used and the extra weight of their larger batteries means they often use more fuel than a conventional petrol or diesel car.

Mild hybrids

Mild hybrids are essentially just petrol or diesel cars so they’re suitable for anyone. In fact, if you switch to a mild hybrid it’s likely to make very little difference to your driving experience or running costs.

You’ll find lots of high-quality used hybrid cars for sale at Cazoo. Use the search function to find the hybrid you love, buy it online, and have it delivered to your door or choose to collect it from your nearest Cazoo Customer Centre.