Here's a chart of a typical electric bike motor efficiency -- peak efficiency is about 85% at 30mph. At 15mph, efficiency is closer to 50%. (that doesn't mean y

Here's a chart of a typical electric bike motor efficiency -- peak efficiency is about 85% at 30mph. At 15mph, efficiency is closer to 50%. (that doesn't mean you get greatest range at 30mph since wind resistance increases with the cube of the rider's speed, so is 8 times greater at 30mph than at 15mph) https://endless-sphere.com/w/index.php/EBike_Efficiency#Determining_Peak_Motor_Output_-_Simple-Cheap_Method https://endless-sphere.com/w/index.php/EBike_Efficiency#Dete... And that's just for the motor, ignoring losses in the generator. Electric bikes don't need perfect efficiency, the Specialized Turbo S has a 700W-hour battery and gives 30 - 60 miles of range (2 - 4 hours at 15mph). A human pedaling at 15mph puts out around 100W, so even if the motor is only 50% efficient, the bike can still travel for 50 miles at that rate on one charge. With a Segway, you stand well over the wheels and can shift your butt (and center of gravity) as far to the rear as possible to make an emergency stop. I don't see how you'd do that with anything resembling a seated bicycle.