The screen uses the most battery. Screen on time is when you actively engage the screen. If you use a phone continuously for 9 hours , not a lot of phones can survive it. Maybe around 5 or 6 phones make that cut. When you go to the battery settings and click on screen , it'll show you how long the screen was actively on , if that number is anywhere north of 6-7 hours, you've got yourself a very nice phone.