To choose the right e-bike, decide in this order: type of bike, motor and battery. Your rides set the type (city, gravel paths, mountain). Hills set the motor: for flat city riding, 40-50 Nm of torque is enough; for mountain riding or climbing with cargo, 85 Nm or more. Distance sets the battery: 400-500 Wh for everyday riding and 625-750 Wh for long rides. Everything else (brakes, drivetrain, brand) comes after.
In the U.S., e-bikes are sorted into three classes: Class 1 (pedal assist only, up to 20 mph), Class 2 (throttle, up to 20 mph) and Class 3 (pedal assist only, up to 28 mph), with motors of 750 W or less. The class decides where you can ride: some bike paths and trails allow only Class 1, and some states set age or helmet rules for Class 3. Check what applies where you live in e-bike laws.
1. The type of e-bike
Almost every type of bike comes in an electric version. The key question is where you’ll ride most of the time.
| Type | What it’s for | Typical tire | Typical weight | What to look for |
|---|---|---|---|---|
| City / commuter | Commuting, errands, around town | 40-55 mm, slick | 44-62 lb (20-28 kg) | Fenders, lights, rack, step-through frame |
| Trekking / hybrid | City and dirt paths, touring | 40-55 mm, mixed tread | 51-62 lb (23-28 kg) | Big battery, short-travel suspension fork |
| Hardtail e-MTB | Gravel roads and easy trails | 2.2-2.6 in knobby | 44-53 lb (20-24 kg) | 85 Nm motor or more, 4-piston brakes |
| Full-suspension e-MTB | Technical mountain riding | 2.4-2.6 in knobby | 49-57 lb (22-26 kg) | Suspension travel for your terrain |
| Electric gravel or road | Long rides on pavement or gravel | 32-50 mm | 26-40 lb (12-18 kg) | Lightweight motor, natural-feeling assist |
| Folding | Combining with trains or transit | 16-20 in | 33-49 lb (15-22 kg) | Folded weight and folded size |
| Cargo | Kids, groceries, deliveries | 20-26 in | 66-99 lb (30-45 kg) | Max total load, powerful brakes |
If you’re torn between two types, the Which bike should I buy? quiz points you in the right direction in seven questions. To see every type of bike, electric or not, there’s the guide to types of bikes.
2. The motor
Mid-drive or hub motor
- Mid-drive motor (at the pedals’ axle). It drives the chain, so it uses the gears: on a climb you shift down and the motor keeps spinning at a good speed. It keeps the weight low and centered, so the bike handles like a regular one. It’s the standard on e-MTBs, touring e-bikes and almost all of the mid and high end.
- Hub motor (in the rear or front wheel). Cheaper, quieter and with less drivetrain wear, because it doesn’t pull on the chain. In exchange, it struggles on long, steep climbs, can overheat and leaves the bike unbalanced. A good option for flat cities and tight budgets.
We compare them using the torque, weight and price of real motors in mid-drive vs. hub motor.
Torque (Nm)
Motor torque, in newton meters (Nm), is the force the motor adds to the pedals. It’s the number you feel most when starting off and on hills, much more than watts.
| Use | Recommended torque | Example |
|---|---|---|
| Flat city riding | 40-50 Nm | Bosch Active Line: 40 Nm |
| Hilly city, touring | 60-75 Nm | Mid-range motors from several brands |
| Mountain, cargo, very steep hills | 85 Nm or more | Bosch Performance Line CX: 85 Nm (previous generation) and 120 Nm (current) |
| Light gravel or road | 35-60 Nm | “Lightweight” motors aiming for subtle assist |
More torque isn’t always better: a very powerful motor weighs more, drains the battery faster if you use its high modes and can feel abrupt in town. Bosch warns on the spec page of its most powerful motor that the highest settings increase wear and reduce range.
Torque sensor or cadence sensor
- Torque sensor: measures how hard you push on the pedals and assists in proportion. Push harder and it helps more; pedal gently and it helps less. It feels natural, like having “extra legs.” Nearly all mid-drive motors have one.
- Cadence sensor: only detects whether the pedals are turning. When you pedal, the motor delivers a fixed amount of help for the mode, however hard you push. It’s cheaper and typical of hub motors. It works, but the assist is less refined and can surge when you start off.
If your city is hilly or you plan to do longer rides, a torque sensor makes the difference.
3. The battery
Capacity is measured in watt-hours (Wh): voltage times amp-hours. That’s the number to compare range by. As a guide:
| Use | Battery | Approximate range in a middle assist mode |
|---|---|---|
| City, 6-20 miles a day | 400-500 Wh | 59-73 miles (94-118 km) on the flat |
| Touring and rides of 40-60 miles | 625 Wh | 71-92 miles (114-148 km) on flat or rolling terrain |
| e-MTB and long rides with climbing | 750-800 Wh | 55-58 miles (88-94 km) in the mountains on knobby tires |
The figures come from our e-bike range calculator for 220 lb (100 kg) of rider and bike. What changes range (assist mode, climbing, wind, cold) is explained in the guide to e-bike range, and the e-bike range by battery chart gives the distance from 400 to 800 Wh in every mode and terrain.
Other things to look at in the battery:
- Integrated in the frame or external. Integrated looks cleaner and is better protected; external (on the down tube or the rack) is usually easier to remove.
- Removable. Essential if there’s no outlet where you park the bike: that way you charge it at home and keep it somewhere mild, as Bosch recommends in its guide.
- Option for a second battery or range extender if you ever want to do long tours.
- A well-known system. Batteries from the major motor makers have replacements and service for years. A battery is a wear part: sooner or later you’ll replace it.
4. The rest of the bike
- Hydraulic disc brakes. An e-bike is heavier and faster on average than a regular bike. On city and touring e-bikes, 180 mm rotors up front; on e-MTBs, 200-220 mm and 4-piston calipers.
- Drivetrain. A 9- to 12-speed derailleur or an internally geared hub (cleaner and longer-lasting in the city). Mid-drive motors wear chains faster: see when to replace your chain.
- Wide tires (45 mm and up on city and touring e-bikes): more comfort and grip, and they let you run lower pressure. Work out yours with the tire pressure calculator, which has an e-bike mode.
- Total weight. If you have to carry it up stairs or onto a train, every pound counts.
- Size. Same as on a regular bike: the bike size calculator points you in the right direction.
How much to spend
There’s no single right budget, but the pattern is consistent across brands. At the lower end of the market you’ll mostly find hub motors, cadence sensors and mechanical disc brakes; as prices go up, mid-drive motors with torque sensors, batteries of 600 Wh or more and hydraulic brakes take over. To see whether an e-bike pays off compared with driving, run the numbers with the bike vs. car savings calculator; what each mile costs in electricity and maintenance is in the e-bike cost per mile chart.
Common mistakes
- Buying the most powerful motor “just in case.” For a flat city, 85 Nm is weight and money you won’t use.
- Looking only at watts. Torque and the type of sensor tell you much more about how the bike rides.
- Comparing batteries by amp-hours. Compare Wh: 14 Ah at 36 V is 504 Wh, and at 48 V, 672 Wh.
- Not test-riding it on a hill. The difference between a torque sensor and a cadence sensor shows up in the first 50 yards of a climb.
- Forgetting where you’ll charge and store it. A non-removable battery means you need an outlet next to the bike.
- Ignoring the law. A motor that assists past 28 mph, more than 750 W or a throttle that pushes past 20 mph takes the bike out of the e-bike classes, and it’s generally treated as a moped or motor vehicle. The same goes for European-style speed pedelecs.
Frequently asked questions
Is a mid-drive or hub motor better on an e-bike?
A mid-drive motor (at the bottom bracket) uses the bike's gears, climbs better and balances the weight better; it's the norm on e-MTBs, touring bikes and mid-range e-bikes. A hub motor is cheaper and simpler, and it's enough for flat city riding, but it struggles on long climbs.
How much torque does an e-bike need?
For flat city riding, 40-50 Nm is enough. For touring with hills, 60-75 Nm. For mountain riding or climbing with cargo, 85 Nm or more: the most powerful e-MTB motors reach 120 Nm.
What size battery do I need on an e-bike?
For city trips of 6-20 miles a day, 400-500 Wh. For weekend rides of 40-60 miles or with lots of climbing, 625-750 Wh. A bigger battery weighs 2-4 lb more, so don't buy more than you'll use.
What are Class 1, 2 and 3 e-bikes?
Class 1 assists only while you pedal, up to 20 mph. Class 2 adds a throttle and also tops out at 20 mph. Class 3 assists only while you pedal, up to 28 mph. Where each class can ride depends on your state and local rules.
Can an e-bike go faster than 20 mph?
Yes, but on a Class 1 or 2 bike the motor stops helping at 20 mph: above that you're on your own. Class 3 bikes assist to 28 mph. Bikes that go faster on motor power, or have more than 750 W, are generally treated as mopeds or motor vehicles, not bicycles.