What is an electric bike and how do they work?

Whether you’re ditching the car by cycling to work or want an easier ride to the top of trails, an electric bike can offer many of the benefits of a non-assisted bike, with motorised power on tap when you need it.

Electric bike technology has advanced at a pace in recent years and you can now find pretty much any type of bike with a motor.

We have guides to the best electric road bikes, best electric gravel bikes and best electric mountain bikes.

If you don’t want to buy a whole new bike, the best electric bike conversion kits will transform your purely pedal-powered bike into an electric bike.

In this general guide to electric bikes, we’ll explain exactly what an ebike is, how an electric bike works, how to ride an ebike and answer some of the key questions you may have before buying.

What is an electric bike?

An electric bike, or ebike, is a bicycle equipped with an electric bike motor to assist you when you’re pedalling. The motor will get its power from a rechargeable battery mounted on the bike.

To classify as an ebike, the motor has to help you rather than propel you on its own. As a result, you need to pedal to get that assistance. How much power the motor delivers is regulated based on how hard you are pedalling and the level of support you have selected.

Electric bike systems offer a number of modes to choose from, allowing you to balance the amount of power supplied through the pedals with range and battery life.

Electric bike laws on how much help the motor can provide, and the speed at which assistance cuts out, vary around the world. But in general the motor is limited to 250 watts output and must cut out when your speed reaches 25kph/15.5mph, except in the USA where it can continue to work up to 20mph.

You can go faster than that, of course, but only under your own effort – the bike’s motor will no longer provide assistance.

How does an electric bike work?

An electric bike will typically have a motor housed either centrally on the bike (often referred to as a mid-drive motor, powered through the cranks) or on the front or rear hub.

Whereas a hub-based motor will push the wheel around directly, an axle-mounted motor will work through the ebike’s chain and gears.

When you pedal, a torque sensor will measure how much effort you are putting in and match that to the motor’s power output.

The idea is that the motor won’t completely take over; instead, you should get consistent power delivery that won’t send the bike lurching forward.

Therefore, one of many benefits of riding an electric bike is you still have to press on the pedals and get exercise. Riding an electric bike for fitness is eminently possible.

Power comes from the battery, which might be mounted on the outside of the frame or hidden within it.

Many batteries can be removed for charging, although others need to be charged on the bike. If that’s the case, you need to have somewhere to park the bike near a power socket.

There will be a controller for the motor, usually mounted on the handlebar or integrated within the frame, that lets you decide how much assistance you want, and to keep an eye on the battery level. Some will include a screen with navigation and other functions too.

Bosch, Shimano, Yamaha, Specialized, Mahle, FSA and Fazua all make popular ebike motors. Specifications can vary significantly and the type of motor found on a bike will depend on its price and the type of riding intended.

For example, an electric road bike is more likely to favour a lightweight system with smooth power delivery, whereas a motor on a high-spec electric mountain bike is likely to offer more torque for off-road capability.

How do you regulate motor power?

An electric bike will usually have between three and five levels of assistance, selected via its controller.

These can give you anything from a gentle push to lots of power for tackling steep off-road climbs, depending on the specifications of the bike’s motor.

Some will also have a ‘boost’ button, which you can use to increase the power output for short bursts of additional power.

Many bikes also offer a walk-assist mode, to make it easier to push when you’re off the bike.

You can change between assistance levels as you ride and there’s usually the option to switch the motor off completely and ride under pedal power alone.

Many ebike motors are designed to be drag-free when switched off, but there is still the additional weight to overcome.

How much weight do the motor and battery add?

Electric bikes are heavier than non-assisted bikes and there’s a wide variation in the weight of ebike motors and batteries.

The lightest systems come in at less than 4kg and are typically found on electric road bikes, but most systems weigh around 6 to 8kg – and sometimes more.

The additional mounting points and frame reinforcement required on an electric bike can add some extra weight, too.

The weight of your system will depend partly on budget, but also the intended use of the bike.

Bikes that require lots of power, for example, an electric cargo bike or e-MTB, are more likely to have a heavier motor and battery package.

An electric road bike requires less assistance and will prioritise lighter weight.

The latest e-road bikes are near-indistinguishable from non-motorised bikes, thanks to the sleek, integrated design of the motor and battery.

The extra weight associated with electric bikes is worth bearing in mind if you need to lift or carry your machine anywhere.

If that’s the case, consider how much extra weight you can comfortably handle.

However, for day-to-day riding, the benefits of having a motor should trump any extra weight, particularly when it comes to climbing… unless you run out of battery.

How do you ride an electric bike?

Riding an electric bike is pretty much like riding a non-motorised bike of the same type.

You switch on the motor, select the assistance level you want using the controller, and then pedal. The motor will make initial acceleration much easier and then help you keep up to speed, particularly when you need to climb a hill.

However, because of the extra weight from the motor and battery, an electric bike may handle a bit more sluggishly than a non-assisted bike.

It may also have wider tyres to carry the extra weight and provide more grip, and it will usually have disc brakes because there’s more mass to slow down and stop.

What range will an electric bike have?

Batteries on electric bikes can give you a range of anything from 20 to 100 miles or more on a full charge, depending on their capacity (measured in watt-hours and abbreviated to Wh). Batteries are expensive, so an ebike with a longer range will, in general, cost more.

You’ll usually get a battery-level indicator, while some control systems will give you an estimated range as you ride or regulate the power output to let you achieve your planned ride distance.

Some ebikes let you plug in a second battery, which might fit in a bottle cage, to up range. You can also lower the assistance level during a ride to help conserve the battery and extend the bike’s range.

While many brands will offer an estimated range for a particular model of bike, and it is possible to gauge a bike’s theoretical range based on its motor power and battery capacity, ultimately it depends on the level of assistance you’re using and the terrain.

Fully recharging the battery from the mains can take anything from around three hours up to nine hours, or more depending on the model, charger and battery capacity.

What types of electric bike are there?

We’ve got a separate guide to electric bike types, but you can find almost any kind of bike with a motor.

The most common types of electric bikes are hybrids and mountain bikes.

The best electric hybrid bikes have flat bars and chunky, puncture-resistant tyres, useful for biking to work, shopping and more leisurely rides.

They may also have mudguards (or the eyelets to add full-length mudguards), a rack and lights, and sometimes have a step-through frame design to make it easier to hop on and off the bike.

Electric mountain bikes normally have a beefy motor with a high torque output to help you get up loose off-road climbs and over obstacles. Once you get to the top, the motor can be turned off to enjoy the downhill ride.

There’s also a growing number of electric road bikes. With drop handlebars, they’re designed to ride fast and are usually relatively lightweight (as far as electric bikes go), to help with handling and hill climbing.

There’s an increasing number of electric gravel bikes, too. With wider tyres to enable you to ride off-road with confidence and drop handlebars for road speed, e-gravel bikes are designed to offer the versatility to really broaden your riding.

The best electric folding bikes will be designed for versatility and compact size. They can be folded up to take on public transport or for easier storage at home/work, so they could be the best bike for commuting for many people.

There are also electric cargo bikes, designed to carry loads for deliveries around town and other day-to-day tasks where they can replace a car or van.

Whichever electric bike you choose, we suggest you read our guides to electric bike insurance and electric bike maintenance to look after what’s likely to be a sizeable investment.

In short, if you want a helping hand on your ride, you can find an electric bike to suit your needs.