iPhone6 running iOS 11 is eating my battery
iOS 11 has severe battery performance issues. Please see the discussion on Apple Communities. Most of the responses show that the problem is common and will not be solved in the short term. (Some users state that even iOS 11.1 beta didn't solve the problem)

For now, the only solution to the problem seems to be downgrading back to 10.3.3.

I hope Apple gets out of this mess as soon as possible.