Shoppers go to Home Depot to buy materials for that home improvement project; not snacks or to fill up the tank. But that may soon change. Starting in December, it will unveil convenience stores with gas stations at four locations around Nashville, Tenn. Car washes also will be added at two of those locations.

If successful, this pilot program could be expanded it to other of the chains' 1,900 stores.

Home Depot also joins a growing list of retailers that provide gas pumps as an extra amenity. Grocery stores such as Meijer, Kroger, Shop ‘n Save and Giant Eagle as well as warehouse clubs like Sam's Club and Costco all have gasoline service.

Energy Analysts International of Westminster, Colo., states that grocery stores' share of gas sales could grow to 12 percent in 2008 from 5.9 percent in 2002.

“There has long been a move towards the one shopping opportunity and this is just the latest offering,” says Todd Hultquist, an associate with the Food Marketing Institute.