Free Android smartphone apps loaded with advertising such as Angry Birds may be a boon for your wallet, but the apps cost your hset some battery life, according to a new study.

Researchers from rdue University in collaboration with Microsoft claim that third-party advertising in free smartphone apps can be responsible for as much as 65 percent to 75 percent of an app’s energy consumption. The study used a specially developed tool to analyze the energy use of 21 Android ndows Mobile apps. The researchers then published an in-depth look at the energy use over a 3G connection of five popular Android apps including Angry Birds, the Android stock browser, Chess Free (the study named it Free Chess), The New York es, Mapquest. The study did not cover iOS apps.

[RETED: ich Smartphone Apps are the Biggest Data Hogs?]

en you fire up Angry Birds on your Android phone, the researchers found that the core gaming component only consumes about 18 percent of total app energy. The biggest battery suck comes from the software powering third-party ads analytics accounting for 45 percent of total app energy, according to the study. And most of that consumption amounts to what is essentially wasted battery drain. The researchers found that more than half of the energy used to serve ads is consumed during what the researchers called the “3G Tail”: energy that is still expended by the app even though the process requiring that power has finished working.

Free Chess was also a big offender when it came to advertising, with 50 percent of that app’s total energy usage dedicated to ads, according to the study. The New York es spent about 15 percent of its total app energy on user tracking, while the Android browser (rendering a Search the mobile version of CNN) spent about 16 percent of total app energy on user tracking.

though they may be cheaper to download use, free apps packed with third-party advertising have a different cost from paid apps. Not only do they appear to be responsible for a big chunk of a free app’s energy consumption, but ads are also becoming more intrusive on mobile devices. A recent report detailed how some advertising companies are using so-called push notification icon ads on Android to sneak ads right onto users’ notification start screens.

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