Although it depends on the quality of channels, watching IPTV for one hour is roughly equal to download a video file with one hour of length. Assuming the size of one hour video varies between 500 to 800MB, this will give you an estimate of how much Internet data is needed for watching IPTV. Accordingly, if you plan to watch IPTV two hours a day, you will need at least 30GB of data traffic per month.
How much Internet data do I need to run IPTV?