E-bikes come with a whole spectrum of different power outputs, from 35Nm right up to 108Nm of torque, and weigh anything from 15kg to 25kg and upwards. So, not only do you have the best electric bikes with max power motors to choose from, there are also the best lightweight electric mountain bikes with detuned motors. And sadly no, you can’t have light weight, high power, and maximum range all in one package (yet), so you’re going to have to compromise somewhere.

Which is why there are now diet e-bikes with limited power and small batteries, mid-weight e-bikes with full-power motors and smaller batteries, and full-fat e-bikes with all the brawn, massive batteries, and hernia-inducing weights.

Choosing which type to buy can be pretty baffling, even for experienced mountain bikers, and an absolute mind-melt for new riders getting into the sport. So, how much power do you need? What are the advantages of going light? And what’s an SL anyway?…

Specialized pretty much started the lightweight revolution with the Levo SL – the latest generation gets more torque and bigger sizing

What is a lightweight e-bike?

We’ve got to get this defined right away, but it’s tricky because not all lightweight e-bikes are easy on the scales, and not all full-power e-bikes are heavy. (The top-end full power Canyon Neuron:ON is just over 22kg for example, while Orange’s mid-power Phase Evo is 20.8kg.) That’s because battery capacity and the bike’s intended use also influence the weight. That said, 20kg is going to be my dividing line between lightweight and full power e-bikes here.

Bosch’s new SX motor has allowed more brands to enter the mid-power party, it delivers 55Nm torque and an impressive 600watts of peak power

Why do lightweight e-bikes deliver less power?

The best lightweight electric mountain bikes top out at 60Nm of torque or less, and they’re all powered by one of four brands’ motors, Bosch, Specialized, TQ or Fazua. Which is the best e-bike motor? That’s a tough call but we’ve got a full breakdown if you want to know more and compare stats.

The low-power output is caused by the motor’s light weight – just under 2kg, saving 1kg over a full power’s unit on average – because the goal is to reduce weight and the visual impact of the system, and that means a power cut is inevitable. They’re also trying to limit the drain on the bike’s battery, the latter is one of the biggest factors in keeping an e-bike’s weight down.

Does weight matter? 100% yes, and to prove it I changed the weight of a Canyon Torque:ON and with it the bike’s ride feel

Lightweight e-bikes are lighter… well, duh

The cool thing about lightweight e-bikes is that they ride differently to full power bikes, they’re easier to throw around on the descents, they’re nimble, and they’re more akin to regular bikes when pedalling. That’s a lot to do with their weight, but it’s not the whole picture. I’ve written before about how weight still matters on a mountain bike – lighter bikes let you jump higher and further, and take less effort to move around in any direction.

The Pivot Shuttle SL is a hooligan on the descents, and one of the best lightweight e-bikes out there because of that

They pedal better on the descents

Lightweight motors are easier to pedal when you’re descending; ride beyond the bike’s speed limiter (25kph in UK and the EU) and there’s less drag and the lighter chassis is easier to accelerate… in fact you might barely notice. Compare that with a full-power e-bike, most of which hit an invisible brick wall when the motor cuts out.

Riding the Mondraker Neat is about as close as you’ll get on an e-bike to that natural bike feel

Lightweights can feel better too

There’s something else going on too, lightweight lightweight e-bikes have smaller batteries than most full-power e-bikes, ranging from 320W to 430W. This is crucial to lowering a bike’s weight. It also does something interesting to the feel and balance of a bike, they don’t suffer from the overly-stiff downtube feel of a full power bike and it makes descending a very natural sensation. Big batteries also extend high up the downtube, and can lead to weird weight imbalances. Brands work hard to keep the battery as low as possible in the frame, and it means loads of new e-bikes now look like the Specialized Turbo Levo SL. And in case you were wondering, SL stands for Super Light for both Spesh and Pivot.

Trek opted for TQ’s motor on the Fuel EXe, which is silent and smooth, but arguably the least powerful system out there

Are you OK with less power?

E-bike power is measured in watts, and the best way to think about that is the amount of work the motor will do. Lightweight e-bikes will typically do 70% of the work of a full power bike, meaning you either have to pick up the deficit and pedal harder and faster, use max power mode and accept less range, or ride more slowly using eco mode. These are the main downsides to a lightweight e-bike; you can’t just razz around in Turbo for three hours barely breaking a sweat. You’ve got to be prepared to work harder for your grins. There’s a battery hack to get round this, which I’ll get to in a second.

The Lumen is Scott’s XC e-bike, and at nearly £15,000 it’s probably the most expensive mountain bike out there

Do lightweight e-bikes cost more?

They most certainly do. The general rule in mountain biking is to make something lighter you have to spend more money on it, all other things like strength and performance being equal. Lightweight e-bikes typically inhabit the most expensive end of the e-bike market, thanks to those components and the fact the technology is so new.

You’ll probably also want to factor in a range extender if you’re getting a lightweight e-bike, they cost £400-£500 and typically add 180-250Wh. Add this to the bike’s internal battery and you’ve got enough to satisfy the hungriest of riders. Of course they add weight, which, you might argue, defeats the purpose of a lightweight e-bike. Although you get to choose whether to lug that extra weight around depending on the ride you’re doing – not a choice you get with a big internal battery. Another slight drawback is that they typically take up the space of your water bottle; only Whyte has figured out how to squeeze both in so far, on the E-Lyte and Mondraker with its Neat and Dune.

At the other end of the scale to Scott’s Lumen is the Specialized Levo SL Alloy, it’s just over £5,000

Are cheaper lighteweights on the way?

They’re already here, albeit with limited choice so far. Earlier this year Specialized launched an alloy version of its Levo SL, costing £5,250, while direct sales brand Canyon just joined the party with its Neuron:ON Fly. Cube’s also in there, with a AMS Hybrid One:44 that looks really good. We’d be amazed if the other direct sales brands like YT didn’t get in on the action soon, and drive the price down further.

Weight and power

Your e-bike has to have the power to move itself around, but the real work is done shifting your weight, which is many times more than even the heaviest eeb. That means if you’re a 100kg rider the motor and battery are going to have a harder time dragging you uphill than a 60kg waif, and the battery and range will suffer accordingly. In my experience the riders who like lightweight bikes the most are on the lighter end of the scale themselves.

Buy a lightweight e-bike if…

You don’t weigh very much. This is for the reasons above, but also because a full-power e-bike will probably feel way too heavy and unmaneuverable, assuming you don’t have the power to weight ratio of an Olympic gymnast. I’ve known lightweight riders get the same range as their full-power buddies.

The number one reason to go lightweight is if you’re suffering from a serious analogue bike addiction, you love the playful ride feel of a normal bike, and the lightweight bike will mimic that feel best.

The Merida eOne-Sixty 875 is a heavy beast but it can give you 1,110Wh of battery power

Buy a full power e-bike if…

You want maximum range with minimum effort. Full power bikes can pack in over 1,000Wh of battery and will undeniably take you further and faster than a lightweight. There’s also something to be said for a heavy bike, it makes the suspension feel incredible thanks to the increase in sprung mass, and they’re incredible at high speeds and over rough terrain.

The lightweight future

The trend in recent years is for full power e-bikes to get lighter, and lightweight bikes to get more powerful. The time will surely come when they’ll meet in the middle, meaning you can have a sub-20kg e-bike with full power and a battery that’ll pack in over 600Wh. You can have your cake and eat it too. When that day comes, my friends, we will have completed e-bikes.