Some researchers from Purdue University, working with Microsoft, took some time to perform a pretty ingenious study. They developed an energy profiling tool called EProf that not only allows them to determine the battery drain of a particular app, but also every thread the app spawns. After testing five Android apps, including Angry Birds, FreeChess, and the New York Times, they reached the conclusion that over 70% of an app's battery drain is caused by ads and not the app itself. They performed their testing on a Nexus One running Android 2.3 Gingerbread. Here's a quote from the TalkAndroid article with an example,
According to their tests, the New York Times only spends about 15% of its battery usage for the app itself, and the rest was from ads. It's important to note, that the researchers were not trying to single out any particular app. They are simply trying to help identify the problems more effectively to add relevant data so that all companies can find more efficient ways to use battery power. In fact, they made their EProf tool an open source, so that developers and advertising companies can develop better ways to minimize battery drain.Lead researcher Abhinav Pathak measured energy usage for one level of Angry Birds and found that the game itself only accounted for about 30% of the total battery drain. The remaining 70% was divided between serving up advertising and uploading user data. The user data is only uploaded once, however the ads are displayed throughout the game, draining the battery continually.
It will be interesting to see how this data might be used to improve things in the future.