The vast majority of power used by free ad-supported smartphone apps is spent running third-party advertising modules, according to a new study.

While testing a new smartphone energy profiling technology on Android and Windows Mobile apps, a team of researchers from Purdue University in the US and Microsoft, found that between 65 and 75 percent of energy used by free apps is dedicated to these modules.

The report – titled “Where is the energy spent inside my app?” – added that in most popular free apps, “performing the task related to the purpose of the app consumes only a small fraction of the total app energy,” just 10 to 30 percent.

The researchers also pointed out that energy consumption of apps has received little attention with apps produced so far having been “largely developed in an energy oblivious manner.”

The study also pinpointed a group of energy issues called “wakelock bugs”, which are for apps to access data when not being actively interacted with. These mean apps can be in high-energy states even when they don’t need to be, draining battery power.

Most energy in smartphone apps is used in input/output processes such as 3G, Wi-Fi and GPS, that are clustered together for a few routines. By focusing on the way in which these processes are carried out, the researchers reduced energy consumption of several  apps by between 20 percent and 65 percent.