What's the difference between a hybrid, a plug-in hybrid, and an electric 'EV' car?

Ed Wiseman
Plugging a vehicle in will soon feel as normal as filling it with liquid fuel – but is it the way of the future? - REUTERS

A ban on conventional petrol or diesel cars seems likely. It won't happen for decades, and the details have yet to be even discussed, let alone confirmed, but it's safe to assume that the simplest powertrain — an internal combustion engine driving the wheels via a mechanical transmission — will one day seem as old-fashioned as a manual choke.

Replacing it is a patchwork of alternatives. As we understand it, all cars will need to be capable of some zero-emission driving; moving without emitting any pollution from the tailpipe. That includes both battery-electric and hybrid cars, as well as a handful of alternatives that remain niche products at the moment.

But what's the difference between an electric car and a hybrid? Why are some hybrids different to others? Is there anything else available? What about hydrogen fuel cells? And is a hybrid an electric car? 

There's a great deal of confusion surrounding this. Car manufacturers' primary concern is selling cars, rather than informing the public about technology, which is why general understanding of these issues can be hazy. What's more, knowledge takes a rather circuitous route from the engineering laboratories to the press (via marketing departments and PR agencies) so some of the information printed on the subject is simply wrong. 

What is an electric car, or ‘EV’?

An electric car is one that runs on, and is ‘charged up’ with, electric power alone. An electric car is only ever refuelled with electricity itself, which enters the car (normally) by means of a charging cable, and never by liquid or other fuel. The electricity is stored in batteries before being used by electric motors to drive the car’s wheels.

This is in contrast to hybrid cars, which have electric elements to their powertrains but which cannot be considered ‘electric cars’ due to the presence of a petrol engine. This point has caused confusion recently, as some manufacturers (and indeed commentators) have incorrectly referred to hybrid cars as ‘electric cars’. 

The Nissan Leaf is an electric car – it has no engine Credit: Max Earey 

Electric cars are becoming commonplace thanks to certain financial advantages, including government grants and the lower cost of “filling up” compared to a tank of petrol. They’re considered better for the environment due to the fact they emit no exhaust gases. Popular examples of electric vehicles (often abbreviated to “EV”) include the Nissan Leaf, Renault Zoe, and Tesla Model S but the choice is expanding rapidly.

Electric vehicles have several key benefits when compared to ordinary petrol and diesel cars, as well as increasingly popular hybrid cars. Electric vehicles emit no pollution at the tailpipe, which means they have a much smaller local environmental impact. They operate very quietly and are generally extremely easy to drive, with no real gearbox to speak of and a great deal of power at low speeds. You can drive an electric car on an automatic-only driving licence.

Most importantly, they can be charged up at home. You can 'refuel' an electric car using an ordinary three-prong plug wherever you find a socket, which is pretty much everywhere. While many owners choose to install a slightly more sophisticated 'plug' at home for faster charging, it's perfectly possible to use the existing setup on your drive or in your garage. Faster chargers, such as those found in car parks and at petrol stations, are also useful for EV owners.

Tesla is a manufacturer of premium electric cars, and is one of the better-known brands Credit: Tesla/AP

Disadvantages include that need to ‘charge’ an electric vehicle, which takes far longer than filling a tank of petrol or diesel – usually several hours in comparison to a couple of minutes. Some electric cars can be half-charged in a shorter time, but this will ordinarily be around 45 minutes. During this time, the vehicle must be physically connected to a plug socket, which makes EV ownership difficult for a lot of buyers unless you own a driveway or have a charging point at work.

Environmentally, there are still big questions as to where the electricity for electric cars will come from, with some critics pointing out that the indirect emissions from electric vehicles are comparable to those of a petrol-electric hybrid. And as with any car, much of its lifecycle carbon output is generated as it's being built. We're optimistic that the building process and indeed the sources of electricity will become cleaner, but for now the electric car remains a relatively niche product.

What is a hybrid, a plug-in hybrid or mild hybrid car?

The term ‘hybrid’ is technically quite vague, but in the context of cars almost always refers to a petrol-electric powertrain. This means the car uses a combination of electricity stored in batteries and petrol stored in a tank to propel the car forward. The details of this arrangement will vary from car to car. 

A hybrid vehicle will almost always be able to charge its own batteries using the petrol engine. In some cases, this is all the petrol engine is there for – to recharge the batteries, which power the electric motors. In other types of hybrid, the petrol motor drives the wheels directly, but an additional battery/motor combination adds some electric drive.

The Suzuki Ignis is a mild hybrid, and one of the cheapest hybrid cars available

In ‘mild hybrids’, the amount of electric power that drives the wheels is limited. The car won’t normally drive on electric power alone, but a small electric motor can be used to fill in the gaps. These systems are cheaper than ‘full hybrid’ models but have a much smaller benefit it terms of emissions.

Some hybrid cars are what’s known as ‘plug-in’ hybrids. As the name suggests, these cars can be plugged-in to the national grid by means of a cable, as you would an electric car. This will charge the car’s batteries, enabling some electric-only range (usually between 20 and 40 miles) and usually reducing the amount of petrol used over longer journeys. This in turn reduces the cost per mile as well as the overall exhaust emissions of the car, when used correctly; there is no requirement to plug the car in (unlike with electric cars) and many owners choose not to.

The Mitsubishi Outlander PHEV is a plug-in hybrid (that's what PHEV stands for)

Examples of hybrid cars include the ubiquitous Toyota Prius, the generously-proportioned Mitsubishi Outlander PHEV, and the the sporty BMW i8. In fact, there are well over 50 hybrid cars currently on sale in Britain, ranging in price from around £13,500 (for the Suzuki Ignis mild hybrid) to more than ten times that (for the top-spec £147,000 Porsche Panamera hybrid).

To make things more confusing, some models are available as a petrol car or as a hybrid. And more bafflingly still, some hybrids have a plug-in option as well as a non-plug-in version. You’d be surprised at how many cars are now available as a hybrid of some description, though – the Volkswagen Golf, Mercedes E-Class, Volvo XC90 and BMW 3-Series are all now available with hybrid powertrains.

The Toyota Prius is perhaps the best-known hybrid car. It's available as a plug-in, as well as a normal hybrid Credit: Richard Newton

The primary reason for using a hybrid car is to reduce the amount of liquid fuel you use. The secondary reason is to be able to drive without emitting any pollution for relatively short distances. Ordinarily, this will save buyers money, as well as reducing damage to the environment. However, it’s important to remember that any savings you make (financial or environmental) will depend on the way in which you use your vehicle, and that the increased cost of buying a hybrid might outweigh the amount you save on fuel.

What do people mean by 'internal combustion', and what is an ICE car?

The car motor as we've known it for the past hundred years is an 'internal combustion engine'. There are several variations on the theme, but they nearly always involve burning a liquid fuel (generally petrol or diesel) inside a cylinder, to move a piston, to create motion. Internal combustion engines were chosen over their rivals (such as the steam engine) because they're relatively well-suited to powering automobiles.

Now, though, the environmental cost is becoming clear. Not only do they normally run on fossil fuels, a finite resource, but the pollution they cause has a harmful impact on both local and global levels. This is why the government has announced plans to stop sales of pure internal combustion vehicles from 2040 onwards.

The internal combustion engine has been the beating heart of British mobility for around a century Credit: Leon Neal/Getty Images Europe

This does not mean the end of the internal combustion engine altogether, however. The technology remains an integral part of hybrid cars – whereas a conventional 'ICE' car uses its engine to turn the wheels directly, a hybrid car uses its engine in conjunction with a battery and electric motor. 

To most consumers, the difference is slight. Apart from quieter operation and reduced fuel bills, many motorists wouldn't notice any change if they swapped a conventional ICE car for a hybrid. The impact of the planned ban on petrol and diesel cars has, it could be argued, been exaggerated.

What about hydrogen – what is a hydrogen fuel cell car?

At the moment, petrol, diesel and electricity are the only practical ways of transferring energy to a car for most people. The millions of plug sockets and thousands of fuel stations make it relatively easy to refuel a hybrid, EV or pure ICE car in Britain, even if there are downsides to both. However, for the more adventurous (and geographically serendipitous) there is another way – hydrogen.

A hydrogen fuel cell car is refuelled with compressed hydrogen. The car itself then turns the hydrogen into electricity, which it uses to drive its wheels. The emission from this process is pure water – clean enough to drink.

hydrogen car puff

The technology is still in its infancy, but there are some clear advantages over fossil fuels, as well as a number of benefits in comparison to plug-in electric vehicles. Hydrogen is generated via a process called electrolysis, which can be done on a small scale in-situ; theoretically, an individual pump or station can create its own hydrogen using on-site renewables or excess electricity from the grid. It can also be pumped into a car quickly, closely resembling the process of refuelling a petrol car.

At the moment, there are only a handful of hydrogen pumps in the UK. The first one at a major fuel station opened earlier this year – we were the first to use it – but we expect this coverage to expand significantly over the next couple of years. It’s too early to recommend this technology to most buyers but hydrogen fuel cell mobility has enormous potential.

Whatever happens, it’s important to remember that technology develops rapidly, and that there’s more to mobility than petrol pumps and charging cables. It is exceptionally difficult to predict what will happen in the 23 years between now and 2040.

Hybrid cars, electric cars, and the 2040 petrol/diesel ban

If this new law is enacted, what will we be left with? Well, pretty much anything you want. It sounds like the only cars that won’t be on sale after 2040 are pure petrol and pure diesel cars, which are a dying breed anyway; manufacturers in every segment are embracing hybrid, electric and other technologies in order to save their customers money and reduce pollution. And remember that the 2040 rule only applies to sales – driving and owning a petrol or diesel car will, as far as we’re aware, also be perfectly legal after this date.

For more motoring news, reviews and features, visit the Telegraph Cars page here.