Smart TVs are moving from novelty to mainstream, with shipments expected to grow 15% worldwide in 2012, according to the latest NPD DisplaySearch Quarterly Smart TV Shipment and Forecast Report.

Connected TV's shipment shares were 26% in China and 34% in Western Europe in 2011. In 2012, it has grown to more than 40% in both regions. Japan has the highest penetration with more than 55%.

"North American households consume the highest levels of internet video, averaging over 30 GB per household every month according to Cisco, yet they don't seem attracted to connected TVs," said Paul Gray, Director, European TV Research. "We find that North America leads by far in paid on-demand services, which tend to be tied to set-top boxes."

Smart and connected TV shipments account for a large percentage of TVs in most regions, but North America seems to be pursuing a different direction. Penetration is hovering around 20%, which is the lowest level of any region.

Critical to the development of connected TV has been the accessibility of content and broadcast services, which have helped propel penetration in Europe and Japan. In China, the availability of attractive free content on the internet has had a similar effect.

Read more over at NPD DisplaySearch.