I don't need it. In fact, I easily get at least 5 hours of screen time (yesterday I got almost 7 hours) with 20 % left at the end of my day. I even have GPS turned on all of the time. I just keep my screen at mid resolution and mid brightness.
Power saving mode set like this. I'm getting over 7.5 hours SOT when connected to my home wifi all day and at that point was only down to 38% left. Not as good battery life when connected to WiFi at work. AND with it set this way, phone is still faster and smoother than my N4.