Hub dynamos are very efficient. I do not feel a difference riding with or without one. For street speeds of around 20km/h in an urban environment they create me

Hub dynamos are very efficient. I do not feel a difference riding with or without one. For street speeds of around 20km/h in an urban environment they create mechanical drag of around 6 watts [1] with the lights switched on. http://www.bikequarterly.com/VBQgenerator.pdf http://www.bikequarterly.com/VBQgenerator.pdf