Your questions answered

What is a range extender (REx) and how do they work?

Range extenders – or extended-range electric vehicles – are an alternative form of electric car. They help eliminate range anxiety while maintaining many of the benefits of purely electric models

Vauxhall Ampera

You'll most likely have come across terms such as electric car, hybrid car and plug-in hybrid car, and even hydrogen fuel-cell car, but the term 'range extender' is perhaps less well known by the general public.

It refers to a type of electric car with both an electric drivetrain (comprised of one or more electric motors and a battery) and an internal-combustion engine. While that's the same basic setup you'll find in a hybrid, the key difference is that in a range extender, the internal-combustion engine functions only as a small generator for the batteries – it never drives the car's wheels directly.

How does a range-extender (REx) electric car work?

Unlike a plug-in hybrid (which usually has distinct electric-only, engine-only and combined electric-plus-engine driving modes) or a full hybrid (which shuffles between the two power sources automatically), a range extender is only ever driven by the electric motor, so it always feels the same from behind the wheel, albeit with a little bit of extra noise if the engine is charging the battery.

Range extenders aren't very common, having been rendered largely obsolete by battery technology and charging infrastructure developments, which have eliminated the range anxiety sometimes associated with early electric cars and given rise to many long-range electric cars. In order to work properly, a range-extender needs to be both refuelled at a petrol station and recharged at a home or public charging point.

What range-extender (REx) electric cars are available?

The BMW i3 was initially offered in both range-extender and pure-electric forms, but the latter has been the only choice for some time now. Another range extender that was sold in the UK was the Chevrolet Volt and its Vauxhall Ampera sister model (pictured top), but both versions of this car have now been discontinued. The technology has since fallen out of favour with most manufacturers.

The big selling point behind range extenders was that they effectively erased range anxiety. This is because the petrol engine not only significantly boosted the vehicle’s range, but also because it could be topped up at regular fuel stations without the need to plug the vehicle in.

Most Popular

Top 10 best seven-seater electric and hybrid cars 2021
Mercedes EQB
Best cars

Top 10 best seven-seater electric and hybrid cars 2021

If the regular crop of electrified SUVs and family cars don’t provide enough practicality for you, then take a closer look at the range of electric an…
24 Nov 2021
Complete guide to the BP Pulse (formerly Polar Plus) charging network
BP Pulse
Your questions answered

Complete guide to the BP Pulse (formerly Polar Plus) charging network

This is how to charge your electric or plug-in hybrid car on the BP Pulse public charging network (which was formerly known as the Polar Plus network)
24 Nov 2021
New 2022 Vauxhall Astra Sports Tourer plug-in hybrid unveiled
Vauxhall Astra Sports Tourer
Vauxhall Astra

New 2022 Vauxhall Astra Sports Tourer plug-in hybrid unveiled

The estate version of the latest Astra continues Vauxhall’s bold new approach to styling and will be available as a plug-in hybrid from launch
30 Nov 2021