Ebikes are designed to assist the rider, making them a great way for those with mobility or cardiac issues. They're a good way of getting back into exercise or while recuperating from surgery or even commuting to work. It's also more environment friendly than any other powered public transport.
With modern ebikes incorporating the battery in the downtube of the frame and the crank drive integrated within the bottom bracket they blend in with standard bikes. The weight of an ebike is around 20-26kg. The extra weight over a traditional bike is offset by the assistance provided by the motor.
A typical ebike has a 250w motor either built into a wheel hub or built into a central unit which drives the crank. A pedal assist sensor ( PAS ) attaches to the bottom bracket area , a dashboard on the handlebar to control how much assist is given and a battery to provide the power. These all connect with cables to a controller that acts like a brain to run the system.
The dashboard has a display offering multiple levels of assistance and a walk feature in case the ebike has to be pushed. The PAS registers the cranks turning and tells the motor to turn. The crank drive uses the force ( torque ) applied to the cranks when pedalling to regulate the amount of assistance supplied.
Because ebikes are similar to regular bikes, those on a budget can buy a DIY kit and convert their current bike into something with a bit more oomph for the hills. The weight of an ekit can be 8-10kg for a 250w system with a 36v battery. For a 1000w ekit with a 48v battery this can add another 8-10kg.
Currently in the UK the legal top speed for an ebike on public roads is restricted to 15.5mph. The motor will switch off after this and any speed generated will be from the rider input. This speed is set by European laws. This speed is lower than other countries such as America which is 20mph. Some ebikes have larger capacity motors capable of higher speeds which if derestricted are for off road or private ground use only. The most efficient set up is with a 250w motor and a large 36/19v battery. A derestricted bike will use up the battery quicker leading to less mileage and a shorter distance achieved, plus a tumble at 15mph is going to hurt a lot less than one at 30mph.
In the UK no licence, insurance, road tax or MOT is required, neither is the requirement to wear a helmet. In the Republic of Ireland you'll need a licence, insurance and a helmet. Maintenance intervals are shorter than standard bikes as brake pads and tyres will wear faster due to the extra power generated.
Ebikes are intended to make cycling easier. If used to riding in excess of 20mph you will be pulling a heavy bike along for most of a ride, so an ebike probably isn't necessary. For most leisure cyclists 15mph is faster than their average so will help regulate speed on sections that usually slow them down eg climbs, increasing overall speed. Plus they're great fun.