I started with a 250 watt motor in the front wheel of my bike but the controller wasn't reliable so I purchased a Felt Bosch Performance mountain bike with a 350 watt motor and it is great. Works wonderfully well and I ride it all the time (3,000 miles in the past year). It does everything I want it to do and when commuting, it gets me up to the legal limit in just a few pedal strokes. When I'm pulling a trailer (about half of those miles), it easily maintains my speed. What benefit would a higher watt motor be? BTW, I'm only interested in legal reasons it would be helpful. I don't want to ride 30+ mph as I don't need my bike to do that. Wouldn't a higher watt motor just burn through the battery faster?