From iOS 8 or higher, now iOS users can monitor all softwares using most battery on their iPhone and iPad.
This feature is built in iOS 8 onwards. You can enable this feature by go to: Settings -> General -> Usage -> Battery usage

In this screen, Apple shows you as 2 columns, the first one lists all applications using the most of battery in last 24 hours, the second one lists applications by the same way but in last 5 days.

However, this page just showing you information, you couldn’t do anything with these applications.
How to save your iPhone, iPad battery life?

In most cases, application listed in the top of the battery usage list means they’ve been used most. For example, look at the picture above, Safari is the top of the list, it means this user spent most of time to browse web.
But not all applications use the same amount of power in the same period. Example, a 3D game will spend more battery than Safari or another simple application.
Therefore, to save your battery life, you should consider the use of applications, especially with heavy graphic application.
Disable unnecessary applications running in background

Applications running in the background are also battery killer. In my case, my iPhone battery life was strongly improved after I disable some no needed applications. Let’s go to: Settings -> General -> Background App Refresh and disable all applications which you think it’s not necessary. For my iPhone, I just enable Gmail and Facebook.
Disable Wifi – 3G when it’s not in use
The internet connection will kill your battery life because a lot of requests will be sent if your iPhone is connecting with a Wifi or Cellular network. In fact, you may need to keep connection for some reasons (For mail updates, stay in touch with friends…). But if you need to save your battery life than any other reasons, you should disable Wifi and Cellular connection.