The best ones are roughly 50% efficient, 10W to output 5W but some are much less, 14W to output 5W. ...and 3W with no load. https://www.cyclingabout.com/how-m

The best ones are roughly 50% efficient, 10W to output 5W but some are much less, 14W to output 5W. ...and 3W with no load. https://www.cyclingabout.com/how-much-do-hub-dynamos-really-slow-you-down/ https://www.cyclingabout.com/how-much-do-hub-dynamos-really-...