What is a hybrid car and how do they work?

Hybrid cars are more popular than ever and there’s a huge range of high-quality new and used hybrid cars to choose from. Hybrids have a petrol or diesel engine and an electrical system that helps improve fuel economy and reduce CO2 emissions and can be a good choice if you want to switch from your petrol or diesel car but aren't ready to go all-electric.

You may have heard of a ‘conventional hybrid’, ‘self-charging hybrid’, ‘mild hybrid’ or ‘plug-in hybrid’. All of these have features in common but there are also some significant differences. Some can be driven on battery power alone while some can’t, and the distance they can be driven on battery power varies widely. One of them can be plugged in to charge, but the others don’t need to be.

Read on and you’ll find out exactly how each type of hybrid car works, its pros and cons and how it compares to the others.

Hybrid cars combine two different power sources – a petrol or diesel combustion engine and an electric motor. All hybrids will help you improve your fuel economy and emissions compared to cars powered by petrol or diesel alone.

The majority of hybrid cars use the combustion engine as the main power source, with the electric motor providing extra power when needed. Many hybrids can run solely from the electric motor for short distances and at low speed. Some of the latest examples can go much further and faster on electric power only, allowing you to commute to and from work without using the engine, therefore saving money on fuel.

A conventional hybrid (or HEV) is also known as a ‘full hybrid’, ‘parallel hybrid’ or, more recently, ‘self-charging hybrid’. It was the first type of hybrid car to become popular 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. They also have an automatic gearbox. The electric motor can drive the car for short periods by itself, typically a mile or so, but it’s mainly used to help the combustion engine. The battery for the motor is recharged using energy recovered by braking or by using the engine as a generator. So there’s no need – and no way – to plug it in and charge it yourself.

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Of all the different types of hybrid, the plug-in hybrid (or PHEV) is the one gaining the most in popularity. Plug-in hybrids have a bigger battery and more powerful electric motor than conventional hybrids, which allows them to travel a greater distance using electric power alone. The range typically varies between 20 and 40 miles, depending on the model, although some can do more, and the capability is growing as new plug-in hybrids are released. Most have a petrol engine and all have an automatic gearbox.

Plug-in hybrids promise much better fuel consumption and lower CO2 emissions than a conventional hybrid, which means they can lower your fuel and tax bills. You need to recharge the battery regularly using a suitable power outlet at home or work, or a public electric car charger, for a plug-in hybrid to work most efficiently. They also recharge themselves on the move in the same way as a conventional hybrid – recovering energy from the brakes and using the engine as a generator. They work best if you do mainly shorter journeys, so you can take maximum advantage of the electric-only range.

Plug-in hybrids combine the benefits of both a petrol car and an electric car. The electric-only range can cover most people’s daily commute with no emissions or noise. And for your longer trips, the engine will get you the rest of the way if you give it enough fuel.

Historically, the Mitsubishi Outlander has been the best-selling plug-in hybrid in the UK, but there’s now a model to suit most lifestyles and budgets. There are plug-in hybrid versions of every Volvo, for instance, and brands such as Ford, Mini, Mercedes-Benz and Volkswagen all offer plug-in hybrid models.

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Mild hybrids (or MHEVs) are the simplest form of hybrid. In essence, they’re a conventional petrol or diesel car with an extra electrical system that helps start the car and assists the engine, as well as powering the main electrical system that runs the air conditioning, lights and so on. That takes some of the strain off the engine, which helps improve fuel economy and reduce emissions, albeit by a relatively small amount. A mild hybrid’s batteries recharge when braking.

A mild hybrid system doesn’t allow the car to drive using electric power alone and as such they aren’t classed as ‘proper’ hybrids. Many car brands are adding this technology to their latest petrol and diesel cars to improve efficiency. Some like to add the label ‘hybrid’ to such cars, but others don’t.

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You’ll see two main benefits of buying a hybrid car – a reduction in your running costs and a lower impact on the environment. That’s because they promise much better fuel economy and lower CO2 emissions while you drive.

Plug-in hybrids offer the biggest potential benefits. Many promise an official average fuel economy of more than 200mpg with CO2 emissions below 50g/km. The fuel economy you get in real world driving will depend on how often you can recharge the battery and how long your journeys tend to be. But if you keep the battery topped up and take advantage of the battery-powered electric range, you should see better mileage than from an equivalent diesel car. And, because exhaust emissions are so low, Vehicle Excise Duty (car tax) costs very little, as does benefit-in-kind tax for drivers of company cars.

Conventional hybrids give similar benefits – fuel economy at least as good as a diesel, and lower CO2 emissions. They also cost less than PHEVs. However, they can only go a couple of miles on electric power alone, so while a conventional hybrid is enough for peaceful low-speed driving in towns or stop-start traffic, it probably won’t get you all the way to work, as some PHEVs can, without using the engine.

Mild hybrids offer slightly better economy and lower emissions than a conventional petrol or diesel car, for roughly the same price. And they’re becoming increasingly common – it’s likely that every new petrol and diesel car will be a mild hybrid in just a few years.

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

Conventional hybrids

Conventional hybrids are a great alternative to petrol and diesel cars because you use them in exactly the same way. There’s no need to recharge the batteries and you simply fill up the fuel tank when needed. They tend to cost more to buy than a petrol or diesel car, but can give better fuel economy and lower CO2 emissions – and, therefore, a lower car tax bill.

Plug-in hybrids

Plug-in hybrids work best if you can take full advantage of their electric driving range. To do that you’ll need access to a suitable power outlet at home, work, or during your journey. They recharge most quickly from a proper electric car charger, though a three-pin plug socket will do if you’re not going to be driving again for a few hours.

Thanks to that longer range, PHEVs can give extremely good fuel economy when compared to an equivalent petrol or diesel car. However, fuel consumption can rise significantly if the batteries run out of charge. Official CO2 emissions are also usually very low, to the benefit of your car tax bill, which could help offset the higher purchase price.

Mild hybrids

Mild hybrids are essentially the same as any other petrol or diesel car, so they’re suitable for anyone. If you switch to a mild hybrid, you’ll likely see a small improvement in your running costs, but little-to-no change in your driving experience.

There are lots of great-value used hybrid cars to choose from at Cazoo. Simply use the search function to find one you love then buy or finance it online. You can choose to have it delivered to your door, or you can collect it from your nearest Cazoo Customer Centre.

We're constantly updating and adding to our stock. If you can't find the right one today, it’s easy to set up a stock alert to be the first to know when we have a hybrid that matches your needs.