By Sam Oliver

Published: 10:45 AM EST

An estimated 12 percent of all U.S. homes have an Apple computer, though nearly all Mac owners also have a Windows PC in their home, a new study shows.

The NPD Group's 2009 Household Penetration Study found that Mac home marketshare has crossed the double digit threshold, up from 9 percent in 2008. However, most Macs live in a "mixed system environment," the study said, with 85 percent of Mac homes having a Windows machine as well.

"Multiple computer ownership is a common thread in Apple computer households, with 66 percent of households owning three or more computers, compared to just 29 percent of Windows PC households," the company said. "Apple owning households are decidedly more mobile as well, with 72 percent of them owning a notebook, whereas only 50 percent of households that have a Windows PC own a notebook."

The study found that Mac owners have more computers than the average consumer, and that extends over to other types of electronics, including iPods and navigation systems. Of those surveyed, 36 percent of computer owners had an iPod. The share among Mac owners, though, was 63 percent. Similarly, while 12 percent of computer-owning households have a digital SLR camera, the total is 32 percent for Mac homes.

The survey was of more than 2,300 online panelists.

"While Apple owners tend to own more computers and more electronics devices, there is also a high correlation among Apple owners and more affluent consumer households,” said Stephen Baker, vice president of industry analysis. "Thirty-six percent of Apple computer owners reported household incomes greater than $100,000, compared to 21 percent of all consumers.

He added: "With a higher household income, though, it's not a surprise that those consumers are making more electronics purchases. "The average Apple household owns 48 CE devices whereas the average computer household owns about 24. Apple household owners' actions and purchases can be used by the industry as leading indicators for hot new products and adoption."



In September, NPD Group reported that Snow Leopard, Apple's latest operating system upgrade, was off to a swift sales start. Mac OS X 10.6 had initial sales twice as high as its predecessor, Leopard, and four times better than Tiger. The study credited Snow Leopard's competitive $29 price for its strong start.

Recent new data found that total online share of Mac systems grew 5 percent in September, following the release of Snow Leopard. That study found that the total worldwide online presence of Macs was a 5.12 percent share.