Free mobile apps 'drain battery faster'

Like many games, Angry Birds has a free version supported by targeted advertising

Free mobile apps which use third-party services to display advertising consume considerably more battery life, a new study suggests.

Researchers used a special tool to monitor energy use by several apps on Android and Windows Mobile handsets.

Findings suggestedthat in one case 75% of an app's energy consumption was spent on powering advertisements.

Report author Abhinav Pathak said app makers must take energy optimisation more seriously.

Free applications typically have built-in advertisements so developers can make money without having to charge for the initial app download.

Mr Pathak told the BBC that developers should perhaps think twice when utilising third-party advertising and analytics services in their app.

The research, produced by at team at Purdue University in Indiana, USA, looked at popular apps such as Angry Birds and Facebook.

Due to restrictions built into Apple's mobile operating system, the team was unable to run tests on the iPhone.

In the case of Angry Birds, research suggested that only 20% of the total energy consumption was used to actually play the game itself.

Of the rest, 45% is used finding out your location with which it can serve targeted advertising.

'3G tail'

The tests were carried out by running the app over a 3G connection. The results noted that many apps leave connections open for up to 10 seconds after downloading information.

In Angry Birds, that brief period - described by researchers as a "3G tail" - accounted for over a quarter of the app's total energy consumption.

Chris McClelland, director of Belfast-based app developer Ecliptic Labs, said he was not surprised by the findings.

"Advertising needs to connect to the server and send information about location," he explained to the BBC.

"That just takes up so much battery. It seeps up the energy."

He said such practices were largely unavoidable if users wanted to enjoy free, ad-supported games and applications.

However, he said developers should give more consideration to energy consumption when building in new features.