I used to leave wifi off since I figured it contributed to battery loss. However, the other morning, I went off to work and forgot that I had wifi on. At the end of the day (evening) before bed, I still had half a battery left. I guess with a good wifi signal at work and at home, I save energy on emails and browsing over using the 4G LTE network.
Bottom line, for my needs (some calls, a few texts, a few pictures, some games and browsing), my phone lasts all day until I shut it off around 9:00. (I'm an old married guy, so I'm not out catting around all night like you young'uns.)