A "class 1 electric bicycle," or "low-speed pedal-assisted electric bicycle," is a bicycle equipped with a motor that provides assistance only when the rider is pedaling, and that ceases to provide assistance when the bicycle reaches the speed of 20 miles per hour. (2) A "class 2 electric bicycle," or "low-speed throttle-assisted electric bicycle," is a bicycle equipped with a motor that may be used exclusively to propel the bicycle, and that is not capable of providing assistance when the bicycle reaches the speed of 20 miles per hour. A "class 3 electric bicycle," or "speed pedal-assisted electric bicycle," is a bicycle equipped with a motor that provides assistance only when the rider is pedaling, (no throttle) and that ceases to provide assistance when the bicycle reaches the speed of 28 miles per hour, and equipped with a speedometer. Local government ordinances are allowed to permit or ban any class of electric bicycles on dedicated bicycle paths and trails, with Class 1 & 2 permitted, and Class 3 banned, by default.
Conversion kits, on the other hand, are sold and installed separately on traditional bicycles. They are harder to setup and conceal, and require some basic mechanical ability and a little bit of ‘elbow grease’ to install. The advantage of conversion kits is that you can choose almost any standard bicycle, and you have the freedom to change or upgrade components as you go. A conversion kit will also allow you to achieve higher power and speed ratings that are not possible on most pre-built electric bike models. Kits are great for tall or heavy riders because they can opt for a larger bike, with higher power and weight carrying capacity. People living in hilly terrain may require the additional torque to handle extremely large inclines. For people who prefer a specific bike model or just love to go faster, a conversion kit offers enormous flexibility.
Because the power is applied through the chain and sprocket, power is typically limited to around 250–500 watts to protect against fast wear on the drivetrain. An electric mid-drive combined with an internal gear hub at the back hub may require care due to the lack of a clutch mechanism to soften the shock to the gears at the moment of re-engagement. A continuously variable transmission or a fully automatic internal gear hub may reduce the shocks due to the viscosity of oils used for liquid coupling instead of the mechanical couplings of the conventional internal gear hubs.
Photo: Could solar power be the future of electric bicycles? The large solar panel mounted over the back wheel of this experimental bike powers an electric motor connected by a chain drive to the back wheel, helping the rider when he doesn't feel like pedaling. Using clean, green solar power would remove the problem of having to charge electric bikes with electricity generated from fossil fuels—and help to extend their range significantly. Photo by Warren Gretz courtesy of US DOE/NREL.
The federal Consumer Product Safety Act defines a "low speed electric bicycle" as a two or three wheeled vehicle with fully operable pedals, a top speed when powered solely by the motor under 20 mph (32 km/h) and an electric motor that produces less than 750 W (1.01 hp). The Act authorizes the Consumer Product Safety Commission to protect people who ride low-speed electric vehicles by issuing necessary safety regulations. The rules for e-bikes on public roads, sidewalks, and pathways are under state jurisdiction, and vary.