When shopping for a new electric bicycle, or “e-bike” for short, there are so many details to consider! Not least among them is: how much power do you want?
E-bike motors come in a range of powers, which deliver an equally diverse range of torque—a.k.a. rotational power—to the bike’s wheels.
You might assume that more power is better, but is that really true? Does it depend on what you’re going to use it for?
For the answers to these and similar questions, fasten your helmets and keep reading, because we intend to find out!
Here’s How Torque Works on Electric Bikes:
Torque is a measure of rotational force, like the force used to make a bike wheel turn. Different amounts of Torque are necessary to perform different tasks; the amount you need depends on your activity. If you’re using more power than you need, your battery will run out sooner than you might like.
How Much Torque Is Enough for Electric Bikes?
Well, that depends on what you use it for!
For instance, climbing steep hills requires a lot more torque than riding along flat roads or bike paths.
The amount of torque you should be looking for in an e-bike is heavily dependent on exactly what you intend to do with that e-bike.
If you intend to take your new bike on challenging mountain paths, you’re going to want as much torque as you can get your hands on.
Conversely, if you intend to use your e-bike to commute long distances across relatively flat terrain, you can get away with much less.
In fact, not only can you get away with less torque in the latter scenario, you might actually want less.
That’s because the more powerful your motor is, the faster it will drain your battery.
Therefore, high-power engines are ideal for short-duration, high-intensity rides, while low-power motors are best for long-duration, low-intensity rides.
Of course, other factors will affect your bike’s suitability for various tasks, such as the battery capacity and motor mounting position, but more on that later.
Additionally, whether or not you intend to haul cargo with your e-bike should figure into the equation when deciding how much torque you need.
If you weigh down a bike bag with heavy objects and/or attach a trailer to your bike, you’re going to need more power to pull the bike along with the cargo.
So going back to the original question, “how much torque is enough,” there is no simple answer; however much power will allow you to perform the tasks you want to perform is enough.
That may seem like a roundabout answer, but don’t worry, keep reading if you want to get into the nitty-gritty to figure out exactly how much power you need.
Please read our article about 15 electric bikes with Bosch motors.
What Other Factors Affect How Strong an Electric Bike Is?
So far, we have yet to define our terms properly; to answer this question and more, we should take a moment to do so.
Torque is a measure of rotational force; it is measured in Newton Meters (N m) and measures the ability of a force to induce rotation.
However, while you might occasionally see a bike’s torque measured in N m, most of the time, you’ll be dealing with a motor’s power output, listed in watts.
There is certainly a correlation—the more powerful the motor, the more rotation it can induce—but it’s important to remember that these are two different things.
This is especially relevant when considering other factors that impact the total torque a motor can produce, such as motor placement.
When choosing an e-bike, you may notice that there are two different standard motor placements available: mid-drive and hub-drive.
- Mid-drive motors sit in the space where the pedal arms attach to the bike frame, directly helping you along as you pedal.
- Hub-drive motors sit on either the front or back wheel and send power directly to that wheel.
Generally speaking, mid-drive motors are more efficient and allow you to get more out of the motor.
For instance, let’s consider a hypothetical 500-watt motor: no matter where you put it on the bike, it’s still a 500-watt motor, but remember how power and torque are two different things?
If we take otherwise identical bikes and identical motors, but mount one on the rear wheel hub, and the other in a mid-drive configuration, you’re likely to get more torque out of the latter.
Even though both motors use 500 watts of power, that power is transferred more efficiently in the mid-drive model, resulting in more torque than the same motor on a hub drive.
There is also one other major factor to consider other than torque itself: your battery capacity.
Granted, this does not directly impact how much torque your bike is capable of producing, but it does affect how long it can generate that torque.
Simply put, the more powerful your motor, the more power you’ll want your battery to store unless you enjoy your pedal-assist giving out halfway through your ride.
The strongest motors drain your battery much more quickly, so you’ll want as much to spare as possible if you hope to use it for an appreciable length of time before recharging.
How Much Torque Do You Need for Riding Up Hills?
If you see torque ratings listed for an e-bike you’re considering, they’ll probably be listed somewhere in a range of 40-80 N m.
In theory, you’ll want to get as close to that 80 N m figure if you intend to climb the steepest hills on your new bike.
However, in practice, the listed torque on any given bike does not tend to be an accurate predictor of its performance in this manner.
This is because there are simply too many variables: the power of the motor, its placement, your weight, the weight of any cargo, the grip of your tires; the list goes on.
So even though we’ve made a point of distinguishing between torque, measured in N m, and power, measured in watts, the latter is often the more useful figure for practical consideration.
To eliminate as many variables as possible, let’s assume a mid-drive mounted motor is the more efficient choice.
With that assumption in place, you’ll likely want at least a 500W motor for moderately hilly terrain.
If you take it to the extreme and want to challenge the steepest of mountain trails, go for a 750W motor; the maximum possible while still being legally considered an e-bike.
How Much Is the Difference Between 350W, 500W, and 750W?
A 750W motor is roughly equivalent to a 1 horsepower engine, so you can think of everything under 750W as a fraction of a horsepower.
One horsepower is defined, roughly, as the force exerted by the average horse to move a 550-pound weight by one foot in one second.
If you’ve ever ridden a horse, you can consider an e-bike driven by a 750W motor as giving you a similar amount of riding power; this is by no means exact but works as a (very) rough estimate.
- Extending that logic, a 350W motor driving the same e-bike would have about half as much power as a horse.
- Practically speaking, a 250W motor is all you need for relatively flat terrain if you want to travel at 20 mph or less.
- A 500W motor is a good all-rounder that can give you appreciable speed on flat terrain and handle moderate hills with relative ease.
If you want to go as fast as possible (the maximum for a class 3 e-bike is 28 mph before the pedal assist shuts off) and/or handle the steepest hills or haul serious cargo, then look to a 750W.
Note that the “full horse” power of a 750-watt motor is situational, and if you’re not hauling cargo, climbing steep hills, or chasing maximum possible speed, you don’t need that much power.
Can Electric Bikes Have TOO Much Torque?
Absolutely; if you’re using more power than you need, your battery will run out far sooner than you might like, for one thing.
Furthermore, if you’re using a high-power motor for jobs that don’t require one, you could wear out your bike, requiring repairs sooner than would otherwise be necessary.
All in all, it’s a good idea to only opt for as much power as you need because overdoing it isn’t going to gain you anything beyond wear and tear and dead batteries.
So tailor your e-bike choice to your intended use.
- A 250-350W motor is all you need for low-intensity rides with little to no cargo.
- If you want versatility and think you might occasionally haul cargo or handle hilly terrain, it’s hard to go wrong with a 500W motor as a versatile option.
- And when it comes to that maximum figure of 750W, you really shouldn’t even be considering it unless you intend to push your e-bike to the absolute limit!