This weekend I took a 22 mile ride (didn't have much time) to see if lowering the level 1% would save much battery power. I lowered the level 1 power to 80%, and could definitely feel a difference in the amount of assist. My average speed went from about 16mph to 13.5mph. Although the terrain is flat, there was a pretty strong headwind of about 10-12mph. At the end of the ride I had about 66% battery charge left (I started at 100%) and according to the app. I could have done a total of about 50 miles. My takeaway is that by lowering the power levels you gain a bit (not much) of battery efficiency, but it's fairly small (maybe 5-10%) so unless I'm taking a really long ride where I'm worried about running out of battery I think I'll keep them set at 100%. Heck, even if it's a long ride I'll probably leave it at 100% and just use the power a bit less, because I'm basically lazy and at 70% or so on level 1 you're really not getting much assist.