The great energy efficiency of bicycles is also their downfall when it comes to using them for generating electricity - you generally produce quite low watts in the context of electricity consumption when pedaling a bicycle. This is not a problem when using it for locomotion, as bicycles are extraordinarily efficient for that purpose, but it does mean that they have very limited utility for electricity production. Basically, even if you’re well trained, you’re unlikely to be producing over 300 watts for a prolonged period of time.