Every e-bike listing shouts a class number at you, and almost none of them explain what it means. Here's the version that actually makes sense.
Most US states have adopted a three-class system. The classes differ on exactly two things: whether there's a throttle, and how fast the motor keeps helping. That's it. Everything else is marketing.
The three classes
Class 1 — pedal assist, up to 20 mph
The motor only helps while you're pedalling, and it stops helping at 20 mph. No throttle.
This is the class with the fewest restrictions almost everywhere. If a trail, park or path allows e-bikes at all, Class 1 is usually the one it allows. If you mostly ride bike paths and multi-use trails, this is the safe choice.
Class 2 — throttle, up to 20 mph
Has a throttle that can move the bike without pedalling, and the motor stops at 20 mph. Most Class 2 bikes also have pedal assist.
The throttle is genuinely useful — pulling away from a light on a loaded cargo bike, getting going on a hill, riding with a bad knee. It's also the feature that makes some trail networks say no, because a throttle bike is closer to a moped in how it behaves.
Class 3 — pedal assist, up to 28 mph
Pedal assist only, but the motor keeps helping all the way to 28 mph. Usually required to have a speedometer.
This is the commuter class. On roads and in bike lanes, 28 mph keeps up with city traffic and turns long commutes into reasonable ones. The trade-off is that Class 3 is the most restricted: many states keep it off multi-use paths and bike trails entirely, several require a helmet regardless of age, and a minimum age of 16 is common.
The bit that isn't in the class number
Underneath the classes there's a federal definition (from the Consumer Product Safety Commission) of a "low-speed electric bicycle": under 750 watts, and no more than 20 mph on throttle alone on level ground. That's what makes an e-bike legally a bicycle rather than a motor vehicle at the federal level.
Two practical consequences:
- A "1000W" or "2000W" bike sold online may not legally be a bicycle where you live, no matter what class sticker it wears. If it goes 35 mph on a throttle, calling it a Class 2 doesn't make it one.
- Class is about what the bike does, not what the label says. A bike that's been unlocked, derestricted, or firmware-flashed past its class limit is out of class, and that matters if anything ever goes wrong.
Which one should you get
Match the class to where you'll actually ride, not to the biggest number.
- Mostly bike paths, trails, parks, riding with kids? Class 1. Fewest places will turn you away.
- Cargo, hills, stop-start city riding, or you want the throttle for accessibility reasons? Class 2.
- Longer road commute where keeping up with traffic is the whole point? Class 3.
If you genuinely want a throttle and 28 mph help, some bikes ship as "Class 2/3 switchable" — throttle capped at 20, pedal assist to 28. That's a real category and it's usually the most flexible option.
For everything about whether the bike itself needs to be expensive, see do you need a good e-bike. Short version: no.
The class doesn't decide the rideout
Worth saying, because new riders worry about it: showing up to a group ride on a "lower" class bike isn't a problem. On a social loop everybody's doing 12-15 mph anyway and the class is completely irrelevant.
Where it matters is when a fast group ride sits at 24 mph for an hour. On a Class 1 or 2, you're pedalling unassisted above 20 the whole time, which is hard work. That's not a rule against you — it's just physics, and it's worth knowing before you sign up for that particular ride rather than finding out at mile three.
Check your own state
The three-class system is common but not universal, and the details — helmets, minimum ages, where each class can go, whether Class 3 is allowed on paths — are set state by state, and sometimes city by city or park by park.
Your state DOT or DMV site is the authority. Where you can actually ride goes through how to find the rules that apply to the specific path you're standing on, which is usually the question you actually have.