The survey released Wednesday found that in addition to the 15 percent of adults who don't use the Internet on any device, another nine percent say they only go online at their workplace.
The report by the Pew Research Center found a whopping 92 percent of these "offline adults" with no interest in using the Internet or email in the near future.
"A lot of people are surprised to discover that not everyone is online," said Kathryn Zickuhr, a Pew researcher and author of the report.
"Most offline adults either don't see the Internet as relevant to them, or feel that it would not be worth the effort. And though many have had some experiences with the Internet in the past, most non-Internet users say they are not interested in going online in the future."
The survey found 34 percent of the offline Americans said the Internet is not relevant to them, that they are not interested, do not want to use it, or have no need for it.
Another 32 percent in this group said they believe using the Internet is difficult or frustrating to use, or cite issues such as spam, spyware, and hackers.
Pew found 19 percent of non-Internet users cited the expense of owning a computer or online connections, and just seven percent said the Internet was not available to them.
The report said the percentage of Americans using the Internet grew sharply from 1995, when just 14 percent were online, but has held in a range of around 75 to 85 percent in the past few years.
Age was a major factor in Internet usage: 44 percent of those 65 and older said they do not use the Internet, compared with 17 percent of the next-youngest age group, 50 to 64.
In the 18-29 age group, 87 percent use the Internet and just 13 percent do not, Pew found
Those with lower incomes or less education, and Hispanics were also less likely to go online.
Some 41 percent who failed to finish high school were not using the Internet, as were 24 percent of Hispanics and 24 percent of those in households earning less than $30,000 per year, according to the researchers.
Urban and suburban dwellers were a bit more likely to go online than their rural counterparts, the researchers found.
But those who are offline are aware of the value of the Internet: 44 of the offline adults surveyed said they have asked a friend or family member to look something up or complete a task on the Internet for them.
And one in four offline adults live in a household where someone else uses the Internet at home, a proportion that has remained relatively steady for over a decade.
One in seven, or 14 percent, of the offline group said they had previously used the Internet, but have since stopped for some reason.
Among the Internet users, most had broadband access, with just three percent using dial-up connections, Pew found.
The report was based on a survey of 2,252 adults from April 17 to May 19. The margin of error was estimated at 2.3 percentage points for the full group, 2.5 points for Internet users and 5.9 points for the non-Internet users.