Battery – in combination with the motor, this determines how far you can get before your bike needs a recharge. Some don’t provide adequate support on even gentle hills, while the best will comfortably take the strain as the gradient shoots up. Range also varies, with the best e-bike systems we’ve tested able to take you nearly twice the distance of lesser models.

Simple, convenient, cheap, and economical—bicycles are one of the world's favorite forms of transportation. But they're not for everyone. They can be hard to pedal up and down hills or with heavy loads, and elderly or disabled people may find them impossible to manage. In the last few years, a new generation of electric bicycles has begun to revolutionize our idea of environmentally friendly transportation. These new cycles have all the convenience of cars with all the simple economy of ordinary cycles. Let's take a closer look at how they work.