The Battery usage screen allows you to see which apps are consuming the most battery power. Information on this screen allows you to identify downloaded apps you may want to turn off when not being used, so you can get the most out of your battery power.
Tap the Home Button > touch and hold the Recent Apps Button > Settings > Battery > Battery usage.
OR
Tap the Home Button > touch and hold the Recent Apps Button > Settings > About phone > Battery > Battery usage.
The top of the Battery usage screen displays a usage graph and below it, battery usage times. It lists all of the apps or services using battery power from the greatest amount of energy used to the least amount.
Tap an app or service in the Battery usage screen to see details about its power consumption. Different apps or services offer different kinds of information, and they may even include options to modify the settings so you can reduce power consumption by that app (or stop running the app).