A Purdue University professor has created an app called Estar that rates other apps based on their energy consumption so users save battery life.

Estar by Mobile Enerlytics is a knight in shining armor for those who are constantly facing dying batteries on smartphones and tablets. Estar features no ads and has a five star rating system for apps. Using this information, smartphone users can choose to download energy-efficient apps with high energy ratings by Estar instead of power-hungry apps found on Google Play Store.

Y. Charlie Hu of Purdue University's school of electrical and computer engineering created an app to help smartphone users find energy efficient apps. Hu built the app after he realized phone manufacturers were ignoring apps' enormous contributions toward battery life consumption. 

"An effective way to extend a smartphone's battery life is to provide users with information about applications' energy efficiency. Users then can choose to download an app that is more efficient than another, if they wish," Hu said in a statement. "There are millions of apps in today's market, and there are several alternatives to almost every popular app."

Hu, CEO and co-founder of Mobile Enerlytics, said the app's main focus is to help users make informed decisions about downloading energy-efficient apps and removing energy consuming apps from their devices. In the end, the consumers win by boosting the life of their smartphones.

Estar app is currently available for Android smartphones via Play Store, but Hu revealed his company plans on creating an iPhone version in the future. The app is well-received by Android users who have rated it 4.5 stars out of a total 5. But Estar has been downloaded only by several hundred users.