E-Bike Motors: The Complete Guide

An e-bike motor is a machine that turns electrical power into twist, and the sticker is three different numbers pretending to be one. Where it sits decides whether that twist can use the gears. A hub motor lives in the wheel and ignores the cassette. A mid-drive lives at the cranks and uses the cassette, so a climb gear multiplies it. The watt figure is either nominal, continuous, or peak, and those are not the same word. The newton-meter figure is either at the axle or at the chainring, and those are not the same measurement. A U.S. low-speed electric bicycle still needs operable pedals, a motor under 750 watts, and a motor-only speed of 20 mph or less. This page is that map. It is not a SickEBike dyno. The long comparison is hub versus mid-drive. The unit fight is 45 Nm versus 65.

How an E-Bike Motor Works

The pack supplies volts. The controller decides how many amps to let through. Watts are volts times amps. That product is the power the motor can turn into rotation, minus what it wastes as heat. A cadence sensor asks whether the cranks are turning, then dumps a level of current. A torque sensor asks how hard you are pushing, then scales the current. A throttle asks the controller to spin the motor whether or not you are pedaling, up to the speed that class allows. None of those sensors changes where the motor is bolted. The watt-hour page is the tank. The power page is why a peak is not the hangtag. The sensor page is the feel.

Hub Motors

A hub motor is built into the wheel. Rear is the 2026 default on a bicycle. It turns that wheel. Your chain still exists for your legs. The motor does not care which cog you picked. That is why a Level 4 REC, an XP4, and an Aventure 3 are hubs. Twist a Class 2 throttle and the wheel turns. On a hill the motor has one ratio: its RPM to the wheel’s RPM. Slow the bike down and the motor RPM falls out of its happy band. Current goes up. Heat goes up. That is a gearbox you did not buy, not a moral failing.

Geared Hub Motors

Most commuter hubs are geared. A planetary set inside the can lets a small, fast motor turn a slower wheel. When you stop pedaling and you are not on the throttle, the hub freewheels, the way a normal rear wheel does. The planetary gears are also the noise and the wear item you cannot see without opening the can. This desk is not telling you to open it. The freewheel is why a geared hub coasts. It is also why that hub does not put meaningful energy back into the pack when you are going downhill.

Direct Drive

A direct-drive hub has no planetary set. The motor’s magnets and the wheel are one ratio. The can is heavier. It does not freewheel the same way, and it can regen, which is the controller running the motor as a generator. This desk’s hub page already files the Level 4’s regen in that direct-drive bucket. Regen on that bike is a claimed extra on the way down. It is not a second battery, and it is not the brake. The brake guide is the stop. A heavier can in the rear wheel is rotating mass. You feel it when you lift the bike, and you feel it when the wheel wants to keep spinning.

Mid-Drive Motors

A mid-drive bolts at the bottom bracket and turns the chainring. Power goes through the same cassette you shift. Downshift and both you and the motor get a lower ratio. The motor stays closer to the RPM it was wound for. That is the hill argument, and it is the chain-wear argument. Bosch Performance Line, the Gazelle Class 1 cards at 60 Nm and 75 Nm, a Tern CX, a Specialized mid, an Aventon Level 4 ADV: those are mid-drives. “Bosch means mid-drive” is no longer a law. The Hub Line on the Lundi 27 is a Bosch hub, 45 Nm, with a 400-watt maximum in the Velomotion block. Cargo and e-MTB are still mostly mid-drives. A Sur-Ron mid-drive in a dirt frame is an e-moto. Pedals and a class sticker are the test. The class chart is that test.

Dual Motors

Two motors are two watt ratings, and you add the nominals if the page is selling both of them as the bicycle. The ENGWE E26 3.0 rates the rear motor at 600 watts and the pair at 2,000 watts peak, with up to 160 Nm. Throttle is listed at 28 mph. Pedal assist is listed at 31. An ENGWE comparison table adds the two motors as 1,200 watts nominal. A 750-watt federal ceiling does not survive a 1,200-watt nominal pair, and 31 mph of assist is not Class 3. Class 3 stops at 28. The page never calls that bike Class 1, 2, or 3. A dual-motor scooter, the NAMI Burn-e 2, is a different aisle again. Do not shop it as a bicycle because it has two wheels and a throttle.

Front vs Rear Hub

Rear is the bicycle default because the drive wheel is already the rear, the chain is already there, and a front hub fights the tire that is steering. On a loose surface or a steep start, a front hub can spin the front wheel before the rear has traction. That is a handling fact, not a mileage claim. The exception this desk has written up is the RadTrike: a Class 2 trike with a 750-watt front hub, on purpose, capped at 14 mph. Three wheels change the traction problem. They do not make a front hub the right default on a two-wheel commuter. If a listing says “dual” and one of them is a front hub, read both watt lines before you read the class word. The E26 is that listing.

Nominal vs Peak Watts

Nominal is the sustained name the class law is looking at. Peak is a burst. The page usually does not say how many seconds. The Level 4 REC prints 750 watts nominal, 1,188 watts peak, and 80 Nm. The arithmetic is on the sheet this desk already published: 36 volts times a 33-amp controller is 1,188. Boost on that page prints 1,440 watts and 96 Nm, and it does not print a duration. The XPedition 2 prints 750 watts and a 1,310-watt peak. The Abound SR prints 1,188 watts peak on Aventon’s table and 950 on Rider Guide, next to the same 750-watt nominal. Do not average 1,188 and 950. Do not shop the peak as if it were the legal watt.

The word in front of the watt is the spec. Nominal, continuous, and peak are three sentences.

Understanding Torque

Torque is twist. It is not speed, and it is not the size of the tank. A high-torque motor can shove a heavy bike away from a light in a low gear and still be capped at 20 mph. A high-watt motor with a small torque number can feel flat until it is spinning. The REC’s 80 Nm and the XPedition’s 85 Nm are hub numbers. Gazelle’s new Class 1 cards print 60 Nm on an Active Line Plus and 75 Nm on a Performance Line. Those are mid-drive numbers. You cannot subtract 60 from 85 and declare a winner. They were taken on different sides of the chain.

Newton-Meters Explained

A newton-meter is one newton of force at one meter of leverage. On a hub, the number is already at the axle, which is the wheel. On a mid-drive, the number is at the chainring, before the gear. First gear multiplies the force at the tire and cuts the speed. A tall gear does the opposite. Bosch, as Velomotion quoted it on 15 September 2026, sets a Hub Line’s 45 Nm next to 65 Nm of a mid-drive and treats them as a similar feeling. That is a feel sentence. It is not a conversion. If an ad says “45 Nm, equivalent to 85 Nm mid-drive,” the second number is a slogan unless they show the gear and the test. Write the hub’s own number. The 45 versus 65 page is only that unit.

250W vs 500W vs 750W vs 1,000W

Five hundred is not “almost 750,” and 750 is not “a 1,000-watt bike with a sticker.” The federal product line this desk keeps using is under 750 watts, plus pedals, plus motor-only speed at or under 20 mph. States then hang Class 1, 2, or 3 on the assist speed and the throttle. A 250-watt Soltera can be a legal Class 1 bicycle. A 750-watt hub can be Class 2 or, if the assist is set to 28, Class 3. A continuous 1,000-watt line fails the watt test before the class word matters. A 2,000-watt peak on a dual-hub fat bike fails it louder. The class chart is the speed half. This table is the watt half.

Hill Performance

On the flat, a 750-watt cadence hub often feels quicker off the line because it does not wait for your legs. That is the Class 2 party trick. On a grade, the hub that won the parking lot has one ratio. The mid-drive in a low gear is using the cassette as a transmission. This desk’s hub page already cites BikeTips, updated September 2026, and Ebike Oracle, May 2026, for a split around an 8 percent grade: under that, a decent hub is enough for a lot of U.S. pavement in the commuter budget; over it, or with a heavy cargo load, you are buying gears for the motor. Chicago’s median block is not that grade. A bridge approach can be. Do not buy the hill motor for a city that does not have the hill, and do not buy the parking-lot hub for a wall.

Motor Efficiency

This desk does not print a brochure efficiency percent. The unit that survives a test is watt-hours per mile, and only when someone rode the bike to empty. Electric Bike Report’s REC loops, already on the Level 4 versus Vorsa page: 43.8 miles in Turbo and 97 in Eco, on a pack labeled 733 watt-hours. Seven hundred thirty-three divided by 43.8 is about 17 watt-hours a mile. Seven hundred thirty-three divided by 97 is about 7.5. Same motor. The assist level did the work. The ADV mid-drive’s loops were 54.6 and 120.8 miles on an 800 watt-hour label. Different tank, different bike. You do not subtract the miles and call the mid-drive more efficient. A motor in its RPM band wastes less as heat. That is the reason a mid-drive can spend fewer watt-hours on a climb. It does not invent watt-hours. Fat tires and a heavier rider will drink more than the motor type will save.

Heat

Heat is the watts that did not become motion. A hub on a long grade is the usual place it shows up, because RPM fell and the controller kept feeding amps. Some hubs cut power. Some cook a winding. This page has no temperature reading and will not invent one. A mid-drive that you leave in a tall gear on the same grade has the same problem, because you refused the gearbox. The fix on a mid-drive is a downshift, not a bigger number on the sticker. The fix on a hub is a shorter grade, a lower load, or a different motor. Opening the can to “add cooling” is not a Saturday job.

Noise

This desk has no decibel sheet. The mechanism is enough. A geared hub’s extra sound is the planetary set. A direct-drive hub is the quieter can, and it is the heavier one. A mid-drive’s extra sound is the chain and the cassette, because that is the path the torque takes. A cadence hub that slams current on at a light is a different noise: the tire, not the gears. If a shop demo is loud, ask whether you are hearing the planetary, the chain, or a brake rub. Those are three repairs.

Reliability

A hub’s failure is often the whole wheel. A shop that can build a wheel can often swap it. A mid-drive’s failure is often a dealer part: Bosch, Shimano, Specialized, TQ. The chain and the cassette are the parts you will actually replace, because the motor’s torque runs through them. The hub-versus-mid FAQ already points at other desks’ chain-life bands. This page does not re-measure them. Water is a separate sheet. An IP number on a bike is not an IP number on the motor unless the motor row says so. The Abound SR fight, IPX5 plus IPX6 versus IPX6 versus IPX4, is why you do not average a seal.

Maintenance

Keep the chain clean and the gears indexed. On a mid-drive that is the motor’s drivetrain, not a hobby. On a hub it is still your legs’ drivetrain. Do not open a hub motor to grease the planetary set unless that hub’s maker sold you the procedure and you already do this work. Do not raise a controller’s amp limit to chase a peak watt. The nominal line is part of why the bike is a bicycle. A bigger amp limit is how a 750-watt sticker becomes the Obsidian problem. Wiring, phase plugs, and a pack that does not match the charger are a fire, not a tune. At your own risk. Work with a mechanic. The maintenance page is the interval list. This page is the reason the chain is on it.

Which Motor Is Right for You?

Buy a geared rear hub if the week is pavement, the grade stays gentle, and you want a Class 2 throttle in the budget where Level 4, XP4, and Aventure 3 already live. Buy a mid-drive if you climb, haul a kid, or ride dirt, and you will pay for chains. Buy the 250-watt Class 1, the Soltera shape, if the legal problem you care about is “no throttle, assist to 20,” not a parking-lot launch. Do not buy a dual-hub bike whose pages add past 750 watts nominal, or whose assist is listed past 28, and then ask which class sticker to peel. There is not one. Read nominal, then peak, then where the newton-meters were measured, then the cutoff speed. Four lines. One motor.

Checked 2 October 2026. Trek’s Ireland Inbound+ page still prints 45 Nm at the rear wheel for the Bosch Hub Line, and it still does not print watts. Notebookcheck’s 85 Nm on that same bike is the fight on the Inbound+ page. Do not average 45 and 85. The Decathlon film above, 27 September 2025, is the older city-hub argument. The August 2026 film is the same split, said by a mechanic, still without a watt.