A team of researchers from Purdue University and Microsoft has discovered that up to 75 percent of app-related battery drain in Android can be caused by ad-serving processes. Led by Abhinav Pathak, the team developed an energy profiler named EProf, which is able to perform fine-grained analysis of the battery use of any Android app, separating each thread inside and recording its energy use. The team tested five popular Android applications including Angry Birds, FreeChess, and the New York Times app using a HTC Passion (Nexus One) running Android 2.3.

In testing Angry Birds, Pathak recorded energy usage for one level of gameplay, and found that less than 30 percent of the app's battery drain was caused by the game itself. The other 70 percent was consumed by the uploading of user information metrics, location, and downloading and displaying of adverts. Pathak notes that although the user profiling occurs only once, new adverts are displayed with each level, causing similar battery drain to occur throughout gameplay.

In FreeChess — a game downloaded over 10 million times — the team started a game and profiled a 33-second period. The test yielded similar results. with around 70 percent of battery drain being caused by ad-related processes. It wasn't only ad-serving apps that wasted battery life on non-essential functions, however, with both the native browser and the New York Times app expending around 15 percent of their total usage performing user tracking.

Pathak explained to us that the team's objective wasn't to expose any particular app or advertising agency for using too much energy, but rather to develop software that can help developers and advertisers to improve the efficiency of their software. Android ads don't have to consume so much energy — they're just poorly coded at the moment, the study suggested. The team plans to release the EProf tool for free under an open-source license soon.

Update: Abhinav Pathak has just reached out to let us know that his team is currently working with Microsoft Research to bring the EProf tool to Windows Phone, in addition to expanding its research on energy efficiency.