Want to drain your smartphone's battery really quickly? Run a lot of apps. Want to drain it so fast that you'll be sprinting for the nearest outlet? Run a lot of free, ad-supported apps. This is the conclusion reached by a team of researcher from Purdue University. They found that third-party ads running in free apps downloaded from the Android Market (now the Google Play Store) could account for a whopping 65-75% of the battery drain coming from an app. That isn't to say that ads themselves are draining three-quarters of a smartphone's battery, just that the vast majority of processing power, memory and data consumption for most free apps goes towards serving ads.
In many ways, that's not surprising; a tip calculator needs only a tiny amount of a phone or tablet's resources to display its interface and make calculations, while a relatively huge amount of data must be sent to your phone to be displayed in a small advertisement. Since most of these ads rotate or swap in and out with app use, it needs to refresh and activate your cellular connection on a regular basis. The study reached its concludions when testing popular apps like Angry Birds, Chess Free, the New York Times, Mapquest and the stock Android browser.
Ads weren't the only culprit for battery loss: user tracking took up a relatively large chunk of energy as well. For example, when using the stock Android browser to do basic web searches, 16 percent of its energy drain was dedicated to tracking the user's behavior. The simple way to remove battery drain from ads is to pay for the premium version of an app. Of course, this isn't always an option - sometimes the free version is the only version, and there's not a lot you can do about Google's pervasive tracking on its own platform. You could use an alternative browser, but the moment you log in to a Google service you're right back to where you started.