Via Green Inc., the answer (sorta) to a question I posed a while back:

Shoppers sitting in their living rooms and ordering items like hair-dryers or cameras online used 35 percent less energy, the study found, than people who shopped the old-fashioned way.

“Customer transport” — in other words, driving to and from the mall — accounted for 65 percent of energy and emissions from the brick-and-mortar shopping method.

Click through for caveats. Lots of them.