Why is my battery draining when switched off?

[iMore Question]

I switched my phone off for the night at 68% charged. It was dead in the morning when I put it on. iPhone 5. Had new battery. Apps off. None running in background. Only got two apps apart from the ones included on phone. Been to Apple shop. No help.

 

[EmceeGeek]

That's very strange. Go into your settings > general > usage > battery usage ; find out what's using the most battery.