Early retail sales estimates released today by the U.S. Department of Commerce for November show total retail sales increased 6.7% in November, but that sales at non-store retailers increased at more than twice that rate, 13.9%. E-commerce and mail-order sales make up more than 75% of the non-store retailer subsector, the Commerce Department says.

On a month-to-month basis, total retail sales increased 0.2% from October to November, whereas non-store retail sales grew 1.5%, the Commerce Department says. The November estimates show that stores continue to lose ground to e-retailers during the critical holiday sales period. Non-store retailer sales accounted for 8.7% of total adjusted retail sales in November, versus 8.2% in November 2010 and 7.8% in November 2009.

Early data for December show the trend continuing. Store sales grew 2.9% year over year for the week ended Dec. 10, according to the International Council of Shopping Centers and Goldman Sachs Weekly Chain Store Sales Index. For the week ending Dec. 9, meanwhile, online sales increased 15.7% compared to the same period last year, per comScore Inc., which tracks web sales. Sales data released today by ChannelAdvisor Corp. show that the company’s e-retailer clients yesterday—a day marketers have dubbed Green Monday—experienced an overall sales increase of 19% compared with the same day in 2010. Yesterday was the second Monday in December, which is typically one of the top sales days for e-commerce.

Consumer electronics is a prime example of a category of product that consumers increasingly are buying online. ComScore estimates that approximately 30% of all consumer electronics sales in the United States are now bought online, and online sales of consumer electronics grew more than 15% during the third quarter versus the same time a year ago.

Best Buy Co. today reported that its same-store sales of consumer electronics declined 4.8% during the third quarter ended Nov. 26, compared with the same quarter last year. The electronics retailer also reported that same-store sales (including BestBuy.com sales) increased almost 1% during the quarter. On its own, BestBuy.com revenue increased 20% year over year during the quarter, Best Buy says. Best Buy is No. 11 in Internet Retailer’s Top 500 Guide.

Store retailers this week also announced that they’ll be extending their hours to capture sales ahead of Christmas. Sears Holdings Corp. (No. 7 in the Guide) says most Sears stores will stay open until midnight starting Wednesday and lasting through Friday, Dec. 23. Department store chain Macy’s Inc. (No. 17) says it’ll have 14 stores open 24 hours a day in the last days before Christmas and another 27 stores will be open until 2 a.m. Meanwhile, web-only retailer Amazon.com Inc. (No. 1) announced today that it is extending its deadline to qualify for free super saver and standard shipping until Dec. 19.