Tests reveal that free mobile apps which display ads eat up your phone's battery

It looks like free mobile apps may be costing you more than you think - at least, when it comes to your electricity bill.

According to a new study by a team at Purdue University in Indiana, the targeted advertising that is often built into free or "lite" versions of mobile software can account for up to 75 per cent of the app's power consumption.

The tests, which were carried out on Android and Windows Phone handsets, looked at highly popular apps like Facebook's free client and Angry Birds.

The research team discovered that 45 per cent of the app's total energy consumption was gobbled up by location-tracking features used to inform the built-in targeted advertising.

A further 25 per cent was devoted to powering the ten-second period of 3G connection that occurs after information is downloaded (known as the "3G tail").

Astonishingly, only 20 per cent of the overall energy consumption was used to power the game itself.

These results came as little shock to Chris McClelland, director of EnergyManager developer Ecliptic Labs.

Speaking to the BBC, McClelland explain that these kind of power-sucking features go hand-in-hand with free apps.

"Advertising needs to connect to the server and send information about location," he said. "That just takes up so much battery. It seeps up the energy."

The researchers at Purdue University were unable to conduct similar tests on the iPhone versions of these apps due to restrictions built into iOS.