The short answer
Most US states sort e-bikes into three classes:
- Class 1: the motor helps only while you pedal, and stops helping at 20 mph. No throttle.
- Class 2: has a throttle that can move the bike without pedalling, and stops helping at 20 mph.
- Class 3: helps only while you pedal, up to 28 mph. Usually needs a speedometer, and some states add age or helmet rules.
Almost every real e-MTB is Class 1. That is also the class land managers allow on mountain bike trails, when they allow e-bikes at all.
Federal law sets a power limit for e-bikes sold in the US (750 watts), and most states use the same figure in their class definitions.
Class 1: the mountain bike class
Class 1 is pedal assist only. You push the pedals, a sensor measures it, and the motor adds a multiple of your effort depending on the mode you choose. Stop pedalling and the motor stops. Above 20 mph it cuts out completely, and you are riding a heavy bike under your own power.
It is the class closest to a regular mountain bike in speed and trail use, which is why it is the one land managers are most willing to allow.
Class 2: throttle bikes
Class 2 bikes have a throttle, usually a thumb lever or twist grip, that drives the bike without pedalling. Many budget, cargo and fat-tire e-bikes are Class 2.
On trails, the throttle is the problem. Most mountain bike trails that allow e-bikes allow Class 1 only, and throttle bikes are usually excluded. Some bikes ship with a throttle that can be removed or disabled; whether that changes their class legally depends on the state.
Class 3: speed pedelecs
Class 3 bikes are pedal assist only, but up to 28 mph. They are commuter bikes, built for roads and bike lanes. Many states restrict them from multi-use paths, and they are rarely allowed on mountain bike trails.
Which class are e-MTBs?
Nearly all purpose-built e-MTBs from established brands are Class 1. They have no throttle and use a mid-drive motor with a 20 mph assist limit for the US market. If you are looking at an "e-mountain bike" with a throttle, it is probably a Class 2 bike with mountain-bike styling, and it will be shut out of most trails.
More on what makes an e-bike trail-worthy in are e-bikes good for mountain biking?
How to tell which class you have
- Look for the class label. Many states require a label on the frame showing the class, top assisted speed and motor wattage.
- Check for a throttle. If there is one, it is not Class 1.
- Check the assist limit. In the display settings or the manual: 20 mph means Class 1 or 2, 28 mph means Class 3.
- Read the manufacturer's spec sheet. It usually states the class directly.
A note on "unlocking" or tuning
Speed tuners and unlocked firmware push a bike past its class limits. That generally takes it out of its legal class, may void the warranty, and is exactly the behaviour that gets e-bikes banned from trails. Do not do it.
Where each class can go, roughly
- Mountain bike trails (where e-bikes are allowed): usually Class 1 only.
- Bike paths and multi-use paths: often Class 1 and 2; Class 3 is often restricted.
- Roads and bike lanes: generally all three classes.
Rules vary by state and by land manager, so check locally. For trails in particular, see where can you ride an e-MTB in the US?
And when someone calls your Class 1 bike a motorbike, the Watts tee has an opinion about that.