Live video can be really compelling, and Facebook is making it easier than ever to watch live content on your smartphone or tablet. The social network said this week that it plans to bump up live videos to the top of users' news feeds with its new Live Video feature, which\u00a0lets people broadcast live video via Facebook.\nBut there's something you need to keep in mind. If you don't have an unlimited data plan, that live video could burn through your monthly allotment quickly, unless you only watch video when you're connected to Wi-Fi.\nLive video rough on data plans, batteries\nHow much data will this live video consume? That depends on a number of factors, including the quality of the video. If you watch standard definition streams, Netflix says it will run you 0.7GB an hour. Chances are you won't stare at your phone's screen for an hour, but even a five-minute video eats up about 58MB of data.\nFacebook Live Video will also drain your phone's battery faster, and that could quickly become an annoyance.\nFacebook is obviously aware that videos make people use its service for longer periods of time, which \u2014\u00a0of course \u2014\u00a0is the point. In a blog post announcing the change to the news feed, Facebook said, "People spend more than 3x more time watching a Facebook Live video on average compared to a video that's no longer live. This is because Facebook Live videos are more interesting in the moment than after the fact."\nThe post does not address the issue of data drain, which is a problem for wireless carriers as well as users. Streaming video accounts for an enormous share of Internet traffic. In November, Facebook said it delivers\u00a08 billion video views per day, or double the amount of views it delivered in April. Much of the activity on Facebook occurs on mobile devices, so that has to be a major strain on wireless networks.\nFacebook Live Video and 'zero rating'\nOne potential solution to the data problem for users would be the so-called "zero rating." If zero rated, Facebook's video traffic would not count against users' monthly allotments. Zero rating is a controversial tactic, however; Facebook tried it in India with its Free Basics service, but regulators saw it as a violation of net neutrality and banned it.\nFacebook could also reduce the quality of its live video, as\u00a0T-Mobile didwhen\u00a0it launched the Binge On offering. I asked Facebook if has similar plans, but have not yet received an answer.\u00a0\nThe bottom line: Live video is cool, and I'm not knocking it. But it could cost you more money than you think.