A recent study at Purdue University revealed some interesting information that may just help businesses sell a few more paid apps.

As it turns out, as much as 75 percent of the energy consumed by free Android applications is actually spent serving ads or tracking and uploading user data for marketers. Popular apps like the free version of Angry Birds or the NYTimes were shown to only use about 10-30 percent of their energy consumption to actually power their core functions.

All this means that running a single free app can completely drain the battery of some smartphones in approximately 90 minutes.

This discovery was made my computer scientists at the university as they were developing a software to analyze the energy usage of different applications. A lot of the energy being used in some of that apps was for things like finding and uploading the user’s location with a GPS to send them location-based ads via a 3G connection.

Much of the energy consumption is blamed on inefficient third-party code that developers include in free apps to turn some kind of profit from them.