How long have you been after update? In my case, it took about 24 hrs for the system to finish indexing etc and going back to normal.
Yeah, I went from 9-10 hours to 7.5-8. Not super sizable drop, but enough to make me upset about the battery life. I mean I can milk Windows 10 for 6-6.5, 7.5 from OS X is pitiful.