Purdue University researchers analyzed battery usage on free smartphone apps, discovering that some of the most popular free apps “spend up to 75 percent of their energy tracking the user’s geographical location, sending information about the user to advertisers and downloading ads.”
These activities can drain your battery more quickly than an energy efficient app. To prevent these apps from draining power, you should switch off your free apps when you aren’t using them on your smartphone.
Check it out: “New findings show that 65 percent to 75 percent of the energy used to run free apps is spent for advertising-related functions … The free Angry Birds app was shown to consume about 75 percent of its power running ‘advertisement modules’ in the software code and only about 25 percent for actually playing the game. The modules perform marketing functions such as sharing user information and downloading ads.”