Riese & Müller have built their bikes to be masters of bike touring. They are some of the only electric bikes that offer a dual battery setup. This means that you are going to be able to go double the distance without recharging. This capability is truly invaluable during a bike tour. On Bosch motors, this takes you from 500 watt hours to 1000 watt hours. There are not any motors offering that type of battery range.
"Bargain Buys" Most electric bikes priced less than $600 at big box retailers and on-line are aimed at the kid/teen/toy market. They generally lack the performance and durability that people want and expect. Also, parts and service can be problematic with both big box retailers and on-line vendors. We urge you to invest in a quality e-bike, preferably from a local dealer, that will serve you (and others) for many years. Remember, if it's poorly constructed and you can't get repair parts, it will likely become land-fill material. Save, beg, or borrow the money to get a quality bike or kit.
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.
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.