There’s little doubt the automotive industry is going through the greatest period of change since the so-called ‘horseless carriage’ was introduced to the world.

It’s been more than two decades since the Toyota Prius popularised the hybrid – with Tesla doing the same thing for the electric car several years later.

However, much has changed in that time. Manufacturers have continued to innovate and find new ways of reducing both fuel consumption and tailpipe emissions, while also catering to different budgets.

Now, there are significantly more powertrain options beyond a choice between petrol or diesel, hybrid, and electric. Here’s what they all mean.

Internal-Combustion (ICE)

The most common type of engine – and the one people are most familiar with – remains the internal-combustion engine (ICE), which uses petrol or diesel fuel exclusively.

These are typically found as inline four- or inline six-cylinder configurations, or arranged in a V-shape to make a V6 or V8 – with V-shaped engines helping to reduce the overall size of the engine block.

Hydrogen Internal-Combustion (H2ICE)

These engines work in an almost identical way to normal petrol engines, but have been designed (or modified) to accept hydrogen as a fuel instead.

While BMW experimented with H2ICE engines in the late 1990s and early 2000s, and Toyota is currently researching the method, carmakers tend to favour hydrogen fuel-cell as an alternative to petrol, diesel, and electric vehicles. More on that later.

Mild-Hybrid (MHEV)

This type of hybrid system is designed to take load off the engine, with auxiliary systems such as power steering and air conditioning – which traditionally work on a belt system run by the engine – instead working on a 12- or 48-volt electrical system.

Mild-hybrid cars will also often use a very small additional battery to power a small electric motor to provide extra torque to the engine during acceleration – where the most fuel is used and the most emissions are produced – working a bit like a powerful tailwind.

Rather than adding an extra electric motor, car manufacturers often use the starter motor for both jobs, or the alternator – which can either harvest electricity on deceleration, or deploy it on take-off.

While a mild-hybrid cannot be driven on electricity alone – and has been given different names by different carmakers – the effectiveness of the system can vary significantly between brands.

Hybrid (HEV)

A traditional hybrid, such as a Toyota Prius or Camry, is often the first thing that springs to mind when the word ‘hybrid’ is mentioned nowadays.

Known in the industry as ‘parallel hybrids’, these vehicles can be driven either by petrol engine or – in very limited circumstances – with their electric motor/s. Typically, the two will work in combination to find the most efficient way to propel the car forward.

However, there’s another type of set-up called a ‘series hybrid’, which is what you’d find in the Nissan X-Trail e-Power.

The Nissan uses electric motors to drive the wheels, but it’s purely petrol-powered – with the small 1.5-litre three-cylinder engine working like a generator to produce electricity for the motors.

Plug-in hybrid (PHEV)

In this instance, the electric motor will drive the car for anywhere between 30 and 100 kilometres before the petrol (or sometimes diesel) engine kicks in.

In a similar way to the parallel hybrid, both the engine and the electric motor/s can drive the car – but in this case, the battery is much larger and can be recharged using an electric-car charger.

Often, the driver can choose whether they want to drive the car with the internal-combustion engine (petrol/diesel) or on electric power – giving them the choice of saving emissions-free driving for the city, where it’s most efficient.

Alternatively, the driver can let the car switch between the two main systems – automatically finding the most efficient way forward.

Then there are other PHEVs, such as the BYD Shark 6 ute, which uses electric motors to drive the wheels like a series hybrid. As with the Nissan e-Power system, the BYD has a petrol motor to generate electricity when needed – but unlike the Nissan, it can be plugged into an EV charger to replenish the battery.

Battery-Electric Vehicle (BEV/EV)

Popularised by Tesla, the electric car is fitted with a large battery that feeds between one and four electric motors.

The earliest EVs of the modern era had around 120-250 kilometres of driving range, but advances in battery technology mean the latest EVs have driving ranges of between 500 and 1000km — and beyond.

Hydrogen Fuel-Cell Vehicle (FCEV)

Rather than swapping petrol for hydrogen in an internal-combustion engine, as in the case of H2ICE, fuel-cell vehicles instead are set up more like battery-electric vehicles – using electric motors to drive the car.

However, instead of receiving electricity from chargers to fill large batteries, the vehicle can instead be refuelled using hydrogen. A fuel-cell is used to convert the hydrogen into electricity, with the only byproduct being pure water.