But that figure was up even more from February 2008 when distribution was at 19%; the increase may have been aided by people mistakenly believing they needed an HD set to be ready for the digital transition, which was originally slated for this past February, now on track for June 12.
In a separate Nielsen report, the company said it found that HDTVs were "the single most popular home entertainment system purchases during the (2008-09) holidays."
Nielsen said HDTVs have the greatest penetration among Asian homes, 42%, and the lowest among African-American homes -- 26%.
HDTVs, Nielsen says, are mostly located (about two-thirds) in common areas, such as a living or family room. Standard-definition sets are not necessarily being discharged but are being shifted to other rooms, where some may be used for "a dedicated purpose, such as video gaming."
The average U.S. household now has 2.6 TV sets.
"As prices of HDTVs continue to fall -- a trend that might accelerate in the current environment -- and circumstances such as the digital transition create new opportunities to promote the sets and programming, HDTV will continue to gain a greater foothold in U.S. television homes," said Nielsen's Steve McGowan, senior vice president, insights and client research initiatives.