There's no getting away from the fact that many electric bikes are pretty heavy. You're looking at a benchmark of around 20kg, and some weigh as much as 5kg more than that. That's a lot of bike to lug about, especially if you live up a few flights of stairs or you have to lift your bike onto a rack, or into your car, or on to a train. So why are they so heavy?
When you're adding a motor system to a bike, that's exactly what you're doing: adding things. There's the motor, and there's the battery, and then there's also some kind of sensor to detect what you're doing, and a display or a remot control (or both), and a control system and wiring loom to tie all those bits together. That's a lot of stuff. On top of that bike manufacturers often beef up the frame to cope with the weight of the motor, and use heavier components in some areas (wheels, for example), so that the bike is reliable. It all adds up.
How much does a motor system add?
All in all, the motor system normally adds up to 8kg to the weight of a bike. The motor itself is generally between 3kg and 4kg, although some units are a bit heavier. The battery will weigh between 2kg and 3.5kg depending on its construction and its capacity: the bigger the capacity, the more it'll generally weigh. Then the rest of the bits and bobs are normally a maximum of 1kg.
Not all motor systems are that heavy, and there are quite a few new players coming into the market whose drivetrains are quite a bit lighter. One we're keeping a close eye on is Fazua – their system with a 250Wh battery is a claimed 4.7kg, and that's for a full-power 250W motor drive. Others are even lighter: the Vivax Assist system, which fits into the seat tube of a bike and drives the cranks directly, weighs just 1.8kg including the battery. That's a different kind of system to your standard city e-bike or electric mountain bike, though, and it's nowhere near as powerful.
So wouldn't you just be faster if you bought a lighter bike?
Well, in many instances you could be. But the appeal of an e-bike, for many people, isn't going fast: it's getting to where you're going with the minimum of fuss, or being able to enjoy a ride without being worried about over-stretching yourself. Having said that, if you've got any serious climbing to do, you'll always be faster on an e-bike. As someone who's ridden up the fearsome Kitzbüheler Horn climb back-to-back on an e-bike and a standard road bike, I know which I'd choose if I wanted to have an enjoyable day out. The extra power easily overcomes the extra weight.
If you don't ever have to lift your bike up or down anything then you'll likely not notice the extra weight on a day-to-day basis, unless you manage to run the battery flat. Pushing an e-bike around isn't hard work and most come with a walk-assist function so it's even easier.
How light can e-bikes be?
If you think you'll struggle with the weight of a standard e-bike then there are options out there that are well under the 20kg benchmark but still offer a full-fat e-bike experience. The Momentum Upstart is 19kg, and it achieves its reasonably low weight by going easy on the gears; there's just two, controlled by an automatic hub.
If your need for gears is greater and your pockets deeper, then Simplon do a street-ready version of their full-carbon Sengo 27.5 mountain bike that weighs in at about 18kg. You won't get much change out of £4,000, but it's a lovely thing to ride and an absolute hoot around town with its top-spec Bosch motor.
If 18kg is too much then the £3,299 Gocycle tips the scales at about 17kg and is a classy-looking thing indeed, although the front motor and smallish battery give it a fairly average range.
It's not quite a thing yet, but Bianchi reckon their E-Doardo will come in at 14kg, and the Focus Project Y prototype, which is a full-carbon mountain bike hardtail with the same Fazua drive, is a kilo less than that. We haven't ridden either yet, even a prototype.
Past that and you're into the rareified air of exotica. Any decent carbon road bike built up with the Vivax system is going to be around the 10kg-11kg mark, and there's also Typhoon who'll build you a similarly-light road bike with a 250W hidden motor, should you ask nicely. And present them with at least €8,000.