Pedal assist (a pedelec) adds motor power only while you pedal. A throttle powers the bike on its own, with no pedaling. That one difference decides how the bike feels, how far it goes, and in many places which legal category it falls into.
How pedal assist works
A sensor detects that you are pedaling and the controller feeds in motor power in proportion to a chosen assist level, from a light eco setting to a strong turbo setting. Two sensor types exist. A cadence sensor only detects that the cranks are turning, so power arrives in steps. A torque sensor measures how hard you push, so assistance follows your effort and feels more natural. Our guide to torque sensors vs cadence sensors covers the trade-offs.
How a throttle works
A thumb lever or twist grip tells the motor how much power to deliver, whether or not the cranks turn. It is useful for starting from a stop on a loaded bike, for riders who cannot pedal continuously, and for short stretches when pedaling is uncomfortable. The cost is that the battery drains faster when you lean on it, and the legal treatment is stricter in several countries.
Side by side
| Feature | Pedal assist | Throttle |
|---|---|---|
| Motor runs without pedaling | No | Yes |
| Effort and exercise | You always contribute | You choose how much |
| Feel | Natural with a torque sensor | On-demand, like a scooter |
| Battery use | Scales with your effort | Drains fast if used alone |
| Legal treatment | Bicycle in most rule sets | Often a separate class or a moped |
What the law says (checked October 2026)
Rules differ by country, state and even trail, and they change. Treat this as orientation and confirm with your local authority before buying or riding.
United States
Federal law defines a low-speed electric bicycle as a two- or three-wheeled vehicle with fully operable pedals and a motor of less than 750 watts whose top motor-only speed is under 20 mph (15 U.S.C. 2085). That definition sets product-safety jurisdiction; where you may ride is mostly decided by states, cities and land managers.
Many of those rules use a three-class system. The National Park Service describes it like this: Class 1 motors assist only while pedaling and stop assisting at 20 mph; Class 2 motors may propel the bicycle on their own and do not assist at 20 mph; Class 3 motors assist only while pedaling and stop at 28 mph. Under the NPS rules, managers may open a trail to some classes and not others, so a throttle (Class 2) bike can be turned away from a path that accepts Class 1.
United Kingdom
The UK does not ban throttles. An electrically assisted pedal cycle (EAPC) needs pedals, a motor of no more than 250 watts continuous rated power, and a motor that cannot propel the bike above 15.5 mph. GOV.UK says an EAPC can be propelled up to 15.5 mph without pedaling, but only if it has been approved. An EAPC needs no license, registration, tax or insurance, and may be used on cycle paths but not on pavements. A bike that exceeds those limits, or has no pedals that can propel it, is classed as a motorcycle or moped and needs registration, tax, a license, insurance and a motorcycle helmet.
European Union
EU vehicle type-approval rules (Regulation 168/2013) exclude pedal cycles with pedal assistance from the moped and motorcycle regime if the motor is rated at 250 W or less and cuts out when you stop pedaling and before 25 km/h. A bike whose motor keeps driving without pedaling does not fit that wording, so how it is treated depends on national rules and on the product standard it was built to. Check your member state before buying a throttle model.
Which should you choose?
- Commuting, fitness, trails: pedal assist, preferably with a torque sensor. It is accepted almost everywhere and uses the battery more efficiently.
- Heavy cargo, hilly starts, limited mobility: a throttle (or a bike offering both) can be worth the extra rules to check.
- Unsure: test ride both, then read the local rules. Our e-bike laws overview, first e-bike buying guide and e-bike vs regular bike comparison help with the next step.
Whichever you pick, never modify the motor, controller or limiter to change speed behavior: it can make the bike illegal on public roads and unsafe to brake and handle.
Sources
- GOV.UK: Riding an electric bike: the rules
- Cornell LII: 15 U.S. Code 2085 – Low-speed electric bicycles
- U.S. National Park Service: Electric Bicycles (e-bikes) in National Parks
- EUR-Lex: Regulation (EU) No 168/2013
Last reviewed: October 2026.