Then question is how high to climb ;-)
My answer is: I use 70% to go uphill +92m on gravel / dry mud.
Then going back down I am back at 40% so is my re-generation.
Depends on tire pressure, % of slope, and own weight and style...
So -7>UP +1>Down on the same slope.
As well happy to share how much energy one can produce:
Here a 700W toaster powered by a "LegStrong" cyclist: https://www.youtube.com/watch?v=S4O5voOCqAQ
Probably the same magnitude of power of the OW's.