Power-assist: Also known as pedal-assist bikes, these are the bicycle equivalents of hybrid cars: they're designed to be pedaled quite a lot of the time and electrically powered either when you're tired or when you feel like a bit of electric help (when you're going up hill, for example). Unlike full-power bikes, they don't have hub motors; instead, there's a separate electric motor mounted near the rear wheel and driving it either through the gear sprocket or simply by pressing against the rear tire. Where a hub motor is difficult or impossible to pedal without any power (because you're effectively turning it into a generator), power-assist motors turn easily with little or no resistance when you pedal. That gives power-assist bikes much greater range than hub-motor ones (as much as 80–145km or 50–90 miles).
The two most common types of hub motors used in electric bicycles are brushed and brushless. Many configurations are available, varying in cost and complexity; direct-drive and geared motor units are both used. An electric power-assist system may be added to almost any pedal cycle using chain drive, belt drive, hub motors or friction drive. BLDC hub motors are a common modern design. The motor is built into the wheel hub itself, and the stator fixed solidly to the axle, and the magnets attached to and rotating with the wheel. The bicycle wheel hub is the motor. The power levels of motors used are influenced by available legal categories and are often, but not always limited to under 750 watts.

First, think about what you need your bike for -- if it's just for a short city commute, in among traffic, then consider a smaller frame that's easy to manoeuvre through cars. The GoCycle G3 (right) is impressively nimble and its electric assistance will help propel you up to 15 mph (24 kph). Better yet, it has built-in lights, automatic gears and you can customise the amount of power the motor provides using a phone app.
An e-bike is identified as a "motor assisted cycle" (MAC) in British Columbia, which differs from electric mopeds and scooters, which are "limited-speed motorcycles." Motor assisted cycles must: have an electric motor of no more than 500 W; have fully operable pedals; not be capable of propelling the device at a speed greater than 32 km/hr [19.9 mph]. The engine must disengage when (a) the operator stops pedaling, (b) an accelerator controller is released, OR (c) a brake is applied. A driver's license, vehicle registration, and insurance are all not required. A bike helmet must be worn.[22]
E-bikes can also provide a source of exercise for individuals who have trouble exercising for an extended time (due to injury or excessive weight, for example) as the bike can allow the rider to take short breaks from pedaling and also provide confidence to the rider that they'll be able to complete the selected path without becoming too fatigued[58] or without having forced their knee joints too hard (people who need to use their knee joints without wearing them out unnecessarily may in some electric bikes adjust the level of motor assistance according to the terrain). A University of Tennessee study provides evidence that energy expenditure (EE) and oxygen consumption (VO2) for e-bikes are 24% lower than that for conventional bicycles, and 64% lower than for walking. Further, the study notes that the difference between e-bikes and bicycles are most pronounced on the uphill segments.[59] Reaching VO2 Max, can really help your body as a whole[60]. Professor Janet Lord of Birmingham University in the UK published a study that looked at older cyclists, ““The study looked at muscle mass, blood cholesterol, their VO2 Max, lung function, and in many of those measures we found they didn’t age! No loss of muscle, their bones were a little thin (but nothing like the general population), their blood pressure didn’t go up.[61]

Another style is the recumbent bicycle. These are inherently more aerodynamic than upright versions, as the rider may lean back onto a support and operate pedals that are on about the same level as the seat. The world's fastest bicycle is a recumbent bicycle but this type was banned from competition in 1934 by the Union Cycliste Internationale.[43]
Being member of European Economic Area (EEA), Norway implemented the European Union directive 2002/24/EC. This directive defined legal ebikes for all EU and EEA countries to cycle "with pedal assistance which are equipped with an auxiliary electric motor having a maximum continuous rated power of 0.25 kW, of which the output is progressively reduced and finally cut off as the vehicle reaches a speed of 25 km/h or if the cyclist stops pedaling." The definition became part of Norwegian vehicle legislation in 2003.[41] A more detailed specification will become effective when the new European ebike product safety standard EN 15194 is published in 2009.
Perhaps the cleverest thing of all about the Electric Brompton is that despite all the extra stuff, it folds up exactly the same as the non-powered variety. It's so simple, and unlike certain folding bikes we could mention, what you're left with is a genuinely small thing, rather than something that's about the size of a bike with the front wheel taken off.