According to a Wall Street Journal study of four recent broadcasts, and similar estimates by researchers, the average amount of time the ball is in play on the field during an NFL game is about 11 minutes...This is why the only way I watch football nowadays is by using a DVR and speeding through the game (and past the commercials).
So what do the networks do with the other 174 minutes in a typical broadcast? Not surprisingly, commercials take up about an hour. As many as 75 minutes, or about 60% of the total air time, excluding commercials, is spent on shots of players huddling, standing at the line of scrimmage or just generally milling about between snaps. In the four broadcasts The Journal studied, injured players got six more seconds of camera time than celebrating players. While the network announcers showed up on screen for just 30 seconds, shots of the head coaches and referees took up about 7% of the average show...
22 September 2012
A football game has only 11 minutes of action
From a 2010 article in the WSJ (the numbers might have changed a bit since then):