The Dash is an excellent, low-cost option for those looking for an intro to e-bikes kind of ride. The TranzX motor will take you up to 28mph for about 16-35 miles per charge–more if you’re conservative with the assist. The components aren’t too shabby either. Shimano M365 hydraulic disc brakes keep you safe, the Shimano Deore SGS drivetrain, and RockShox Paragon fork with 65mm of travel make it a great entry level option.
On the other end of the pricing spectrum (although not as high-end as possible) falls the Riese & Muller lines. The Nevo line, which features a Bosch motor, hydraulic disc brakes and speeds up to 28 mph also has a roughly $5,000 sticker (a variety of models allows for a cheaper price). Using a carbon belt and Nuvinci grip shifter, maintenance worries lessen. The German-made premium models are hand made to specifications and comfort reigns supreme.
Duke Eco-Marathon Team using an Electric Bike Technologies hub motor for the 2014 Shell Eco-marathon. The E-BikeKit motor provides optimal space saving because it does not require a chain (this makes it great for converting road bicycles to electric bicycles, which is what it is designed to do) but we hope to determine if it provides us with a better overall vehicle efficiency than our outboard motor.
For many bikes, battery range is more important that total power (because they're all pretty powerful). You want a bike that delivers a range long enough for your rides at the power levels you want. Most e-bikes will have three to five levels of assist kicking in anywhere from 25 percent of you pedal power to 200 percent boost. Consider how fast the battery takes to recharge, especially if you'll be using your bike for long commutes.