What is an electric bike and how do they work? Buyer’s guide to ebikes

Freda Walters

Whether you’re ditching the car on your commute to work or want an easier ride to the top of trails, an electric bike can offer many of the benefits of a regular 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, from e-road bikes and e-MTBs, to e-hybrids and e-gravel bikes.

In this 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.

Thinking about buying an electric bike?

If you’re thinking about buying an ebike, take a look at our latest electric bike reviews.

Or if you want our pick of the best electric bikes, as tested by the BikeRadar team, check out the buyer’s guides below.

What is an electric bike?

An electric bike has a built-in motor and battery to provide assistance when pedalling.

An electric bike, or ebike, is a bicycle equipped with an electric 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.

Ribble electric hybrid bike with child on seat

Electric bike assistance is limited to 15.5mph in the UK, EU and Australia.

Regulations about 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.

According to the Department for Transport (in the UK), for a bike to be classified as an electrically assisted pedal cycle (EAPC), it must have pedals used to propel it, and meet the following requirements.

It must show either: 

  • the power output 
  • the manufacturer of the motor 

It must also show either: 

  • the battery’s voltage 
  • the maximum speed of the bike 

Its electric motor: 

  • must have a maximum power output of 250 watts 
  • should not be able to propel the bike when it’s travelling more than 15.5mph

How does an electric bike work?

Ribble electric hybrid bike

Press on the pedals and an electric bike will offer motor assistance.

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.

The Ribble Hybrid AL e eBike is equipped with a SRAM drivetrain

Electric bike motors are housed either in the middle of the bike or, as pictured here, one of the wheel hubs.
Russell Burton / Immediate Media

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?

Ribble electric hybrid bike button on top tube

You can usually control the level of assistance with a frame-mounted button, as pictured here, or handlebar-mounted controller.

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.

Ribble electric hybrid bike for commuting

Many ebikes offer a walk-assist mode for easy off-the-bike pushing.

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?

Ribble electric hybrid bike

Electric bike motor systems are getting lighter, but watch out for weight if you need to lift or carry your bike.

Electric bikes are heavier than regular 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, whereas 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.

Ribble SL e electric road bike

Some of the latest electric bikes look just like non-motorised bikes.

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?

Ribble electric hybrid bike

Riding an electric bike is as easy as, well, riding a 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 regular 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?

Ribble electric bike

Range depends on the motor type and battery capacity, as well as your riding style and the terrain.

Batteries on electric bikes can give you a range anywhere 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.

The 250w battery is integrated in the down tube on the Ribble Hybrid AL e eBike

If the battery is integrated within the frame, you’ll need to be able to access the mains to charge the bike.
Russell Burton / Immediate Media

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 bike with a motor.

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

Electric hybrid bikes have flat bars and chunky, puncture-resistant tyres, useful for cycling 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.

Ribble Step Through electric hybrid bike for commuting

Some hybrid bikes have a step-through frame design to make it easier to hop on and off.

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.

Ribble CGR electric gravel bike

Electric gravel bikes are designed to combine off-road capability with on-road speed.

There’s an increasing number of electric gravel bikes, too. With wider tyres to let you 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.

A folding electric bike will be designed for versatility and compact size, so that it can be taken on public transport or folded up for easier storage at home/work.

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.

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

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