Across Europe, where e-bikes were embraced by the public long before the rest of the world, e-bike growth has averaged in excess of 20 percent each year between 2014 and 2017, with a whopping 25.3 percent growth to a total of two million e-bike sales in 2017. Analysts predict that strong growth will continue, with worldwide e-bike sales expected to hit $23.83 billion by 2025. A lot of that growth will be right here in the US.
Since cyclists' legs are most efficient over a narrow range of pedaling speeds, or cadence, a variable gear ratio helps a cyclist to maintain an optimum pedalling speed while covering varied terrain. Some, mainly utility, bicycles use hub gears with between 3 and 14 ratios, but most use the generally more efficient dérailleur system, by which the chain is moved between different cogs called chainrings and sprockets in order to select a ratio. A dérailleur system normally has two dérailleurs, or mechs, one at the front to select the chainring and another at the back to select the sprocket. Most bikes have two or three chainrings, and from 5 to 11 sprockets on the back, with the number of theoretical gears calculated by multiplying front by back. In reality, many gears overlap or require the chain to run diagonally, so the number of usable gears is fewer.
I would advocate you ride legal within the laws of your state. I would also look into some kind of liability rider or umbrella policy with your home owner’s policy, which covers your personal liability and theft. Get your bike registered; wear your helmet, eye protection, whatever is required by state law so that if an accident occurs and you are at fault, there is no legal recourse. Even if you own a 750W/20mph ebike that meets the definition of a bicycle, any at-fault cyclist may still be denied coverage by stingy insurance companies who want to support their clients. Your health insurance will usually cover your medical bills, but the costs of an expensive ebike may be lost.
Chart: Electric bicycles are rapidly becoming popular. This chart shows the growth in sales of what the manufacturers refer to as "electric power-assisted cycles (EPACs)" in European countries over the last decade. Over 1.6 million electric bikes were sold in Europe in 2016 alone, which is about 7 percent of total European bicycle sales. What this chart doesn't reveal is that the bikes are much more popular in some countries than others: four countries accounted for 70 percent of all the sales (Germany, 36 percent; the Netherlands, 16 percent; Belgium, 10 percent; and France 8 percent). Data sourced from the report "European Bicycle Market: 2017", courtesy of CONEBI (Confederation of the European Bicycle Industry). These are the newest figures available at the time this article was last updated (September 2018).
Electric bicycles have two main methods of operation: pedal-assist and/or throttle-control. As the name implies, pedal-assist “assists” your pedaling and requires some input. With this method, a torque sensor picks up movement or stress to determine the power requirements of the rider. Everything is automated so there’s nothing to think about, just jump on and start riding. Some bikes have multiple settings, while others have just one setting with the addition of a throttle control. Depending on the setting, pedal-assistance can help a little – or a lot. At lower settings, pedal-assist is barely noticeable but helps extend your range. At higher settings, the power is quite obvious and feels like a strong wind at your back with the motor doing most of the work while you pedal along.
In Norway, e-bikes are classified as ordinary bicycles, according to the Vehicle Regulation (kjøretøyforskriften) § 4-1, 5g. Hence, e-bikes are not registered in the Vehicle Registry, and there is no demand for a license to drive them. Still, there are constraints on the bicycle construction. The maximum nominal motor power output can be no more than 250 watts and the maximum performance speed of the vehicle when the engine is running is 25 km per hour (15 mph). A function that reduces motor power when vehicle speed exceeds 25 km per hour is mandatory. However, if the motor is not running, the e-bike, or any other bike, answer only to the constraints of the ordinary speed limits.
Parliament has decided to approve the speed pedelec – a type of super electric bike that can reach speeds of up to 45 km/hour – for riding on cycle paths. Danish Parliament has decided that as of July 1 2018 those operating the super bikes only need to have turned 15 and wear a helmet, while the licence and number-plate demands will no longer be in play.