The case for online shopping

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This really comes down to scale. All products have to be shipped from the warehouse where they're stored after manufacture, and it can be quite a bit greener to cut the retail store -- and all the building, lighting, cooling, heating, and so forth that the store requires -- out of the equation. According to the Center for Energy & Climate Solutions, shipping two 20 pound packages by overnight air -- the most energy-intensive delivery mode -- still uses 40 percent less fuel than driving 20 miles round-trip to the mall or store or wherever you're going; ground shipping -- which is much more efficient than overnight air -- checks in at just one-tenth the energy used driving yourself.
How does that work? While your car is likely to get more miles per gallon than the truck that's likely shipping your stuff (truck freight accounts for about 2/3 of U.S. domestic shipping), your car only has you (and maybe a passenger), while the truck can be hauling up to about 30 tons of cargo (that's a fully-loaded truck at the legal limit for gross vehicle weight). So you, your buddy, your car, and your 40 pounds of package (on the way home) burn about one gallon of gasoline in those 20 miles.
Shipped 1,000 miles in a truck, your package accounts for about 0.1 gallon, and if you choose to ship by air freight, that number hops to 0.6 gallons; it's all thanks to the hundreds of other packages that are presumably along for the ride. And, even though your online order doesn't go from warehouse to your front door in the same loaded truck or airplane, companies like FedEx and UPS are working to upgrade the efficiency of their routes and fleets, since faster, more-efficient service saves them money.

http://www.thehomeofonlineshoppers.com/