New York, Sep 2 (IANS): Are you frustrated by the limited battery life of your smartphone? No need to fret any longer as a US professor has created a free app called Estar that reveals how certain apps drain a smartphone battery faster.

Estar offers two energy efficient alternatives -- and the first is to search for energy-efficient apps in Google Play.

It displays a colour-coded, five-star energy rating for each app that shows how fast an app will drain the phone battery relative to other apps in the same category.

"Users can then use this information to make decisions on which apps they choose to download," Y. Charlie Hu from Purdue University's school of electrical and computer engineering was quoted as saying.

The second option is to report on the energy drain of apps already downloaded and running on the user's phone.

"It identifies and warns the user which apps are draining an excessive amount of battery. The user can then take action such as stopping or removing the app to extend battery life," Hu told the website Jconline.com.

Estar is available for free in Google Play.