I have had my iPhone 6 for almost a week and a half and have never gotten more than 6 hours of usage. Right now it's 20% and I'm at 4 hours 45 mins so we will see how it goes. Extremely disappointed by my battery so far. I even have background refresh disabled, stripped location sevices to minimum, turned off push for email, it's fetch for only one of my 4 emails, manual for the rest. Brightness usually 25%. What's the deal?!
Now at 5 percent and at 5 hours 15 minutes of battery usage. 15 percent in half an hour of Twitter, Safari, Messages, and a small little game I play at absolute darkest the screen will get. Help..?
The iPhone battery when used as a full smartphone without worry about battery will give about 6-7 hours. Just got to accept that I guess.
Which means that if you want longer battery you might want to consider the 6 plus. Return the 6, try the 6 plus and then return it within 14 days if you need.