Almost every e-bike is 250W, because that is the legal limit. So the wattage on the box tells you nothing about how two legal bikes differ. The number that does is torque, in newton metres.
What the 250W actually refers to
Under UK law an electric bike is an EAPC — an Electrically Assisted Pedal Cycle — if its motor is rated at no more than 250W continuous, assistance cuts out at 15.5mph, and the rider is 14 or over. Meet those and it is legally a bicycle: no licence, no registration, no insurance, no road tax.
Because that figure is fixed by law rather than by engineering, every road-legal e-bike in Britain shares it. Comparing two bikes on continuous wattage is like comparing two cars on the fact they both have four wheels.
Torque: the number that changes the ride
Torque is rotational force — how hard the motor twists, rather than how fast. You feel it at the moment you push off, and on a steep pitch where the cranks are turning slowly. It is measured in newton metres (Nm) and mid-drive motors currently sold in the UK run from about 40Nm to 120Nm.
| Torque | What it feels like | Suits |
|---|---|---|
| 40–50Nm | A helpful hand. Gentle, and easy to ride with the motor off. | Flat commutes, towpaths, town riding |
| 55–75Nm | A firm shove from standstill; most British hills stop being an event. | Hilly commutes, general trail riding |
| 85–120Nm | The bike climbs things you would previously have walked. | Steep loose climbs, heavy loads, mountain use |
Why more is not automatically better
- Chains and cassettes wear faster. A high-torque motor puts more force through the same drivetrain a normal bike uses. Budget for more frequent chain replacement.
- It is heavier. High-torque motors and the bigger batteries that usually accompany them add weight you carry every ride and every time you lift the bike.
- It is harder to ride smoothly on the flat. A very strong motor in a high mode can feel abrupt at low speeds in traffic.
- It costs more. Torque is most of what separates price points within a manufacturer’s own range.
How to choose in one question
What is the steepest hill you have to climb from a standing start, with whatever you normally carry? If the answer is “nothing much”, 50Nm is plenty and you will enjoy the lighter bike. If it is a 15% pull out of a valley with panniers, look at 75Nm and up. If you are riding steep loose off-road climbs, that is where 85Nm and beyond earns its weight.
What we stock, and why that is not a contradiction
Our own electric bikes start at 75Nm and run to 120Nm, so if the advice above points you at a 50Nm town bike, we do not sell one. We would rather write the honest guide and lose the sale than pretend the bottom of the market does not exist. If a light, gentle e-bike is what your riding needs, buy one — and if you are not sure which side of that line you fall on, tell us your route and we will say so plainly.
Two numbers you can safely ignore
Peak watts. Manufacturers quote 600W, 810W and similar. It is the short burst the motor can deliver and it is real, but it is not comparable between brands because nobody agrees how long “peak” lasts.
Top speed. It is 15.5mph on every legal e-bike sold in the UK. A higher figure means the bike is not an EAPC.
We put torque and battery capacity on the front of every electric bike page, because those are the two figures worth comparing.