Apps are what make our smartphones way more than just a voice device and the great thing is that so many of them are free. But you may not realize that there may be a hidden cost to those free apps akin to 'there's no such thing as a free lunch'. A couple of the potential costs include battery life and excessive use of your cellular data. Much research has been generated around the use of free apps because they are so popular and the results show that free apps can eat up your data plan. In addition to reducing your data plan loading ads in the background, that process also requires more battery power and your working memory, which can reduce all-around performance. If you get a data usage warning far before the end of your monthly billing cycle or you find yourself out of juice in the middle of the day, it might be good to watch to see how many apps are serving up ads. Another way free apps pay for themselves is by sharing data about you and your usage, so consider that cost as well. Keeping all this in mind, when an app is available for free or as an ad-free version for a few dollars, paying for the app could be much more cost-effective.