Half of American households have a TV connected to the internet

"New consumer research from Leichtman Research Group (LRG) finds that 49 per cent of all US households have at least one television set connected to the Internet via a video game system, Blu-ray player, Smart TV set, and/or stand-alone device (such as Roku, Apple TV, or Google Chromecast) – up from 38 per cent in 2012, and 24 per cent in 2010. Overall, 24 per cent of adults watch video from the Internet via a Connected TV at least weekly, compared to 13 per cent two years ago, and 5 per cent four years ago.
Connected television use is heavily skewed towards Netflix subscribers, with 49 per cent of Netflix subscribers watching video from the Internet via a connected device weekly, compared to 8 per cent weekly use among all non-Netflix subscribers. Among Netflix streaming video users, 78 per cent say that they watch Netflix on a TV set — a similar level to the previous three years.
These findings are based on a survey of 1,211 households nationwide, and are part of a new LRG study, Emerging Video Services VIII.
Other related findings include:
80 per cent of all Netflix subscribers also subscribe to a pay-TV service – compared to 85 per cent in 2012, and 88 per cent in 2010
48 per cent of all non-subscribers to a pay-TV service get Netflix — compared to 29 per cent in 2012, and 16 per cent in 2010
15 per cent of Netflix subscribers agree that their Netflix subscription is shared with others outside their household
47 per cent of households get Netflix, Amazon Prime, and/or Hulu Plus
On a daily basis, 31 per cent of adults watch video on non-TV devices (including home computers, mobile phones, iPads, tablets, and eReaders), and 58 per cent weekly – up from 18 per cent daily, and 46 per cent weekly two years ago
Including Connected TV sets, 34 per cent watch any over-the-top video daily, and 61 per cent weekly"
Source:  Advanced Television, 9th June 2014
Note - This is the first study I've seen to include things like Chromecast in the broad definition of connected TV