NORTH CANTON, Ohio – A simple change to the design of the gallon milk jug, adopted by Wal-Mart and Costco, seems made for the times. The jugs are cheaper to ship and better for the environment, the milk is fresher when it arrives in stores, and it costs consumers less.

What’s not to like? Plenty, it turns out.

The jugs have no real spout, and their unorthodox shape makes consumers feel like novices at the simple task of pouring a glass of milk.

“It spills everywhere,” said Amy Wise, a homemaker.

But retailers are undeterred by the prospect of upended bowls of Cheerios. The new jugs have many advantages from their point of view.

Experts say the redesign of the milk jug is an example of the changes likely to play out in the American economy over the next two decades. In an era of soaring global demand and higher costs for energy and materials, virtually every aspect of the economy needs to be re-examined, they say, and many products and procedures must be redesigned for greater efficiency.

Pulling that off is vital to lowering the nation’s energy usage without hurting itsquality of life.

“This is a key strategy as a path forward,” said Anne Johnson, the director of the Sustainable Packaging Coalition, a project of the nonprofit group GreenBlue. “Reexamining, ‘What are the materials we are using? How are we using them? And where do they go ultimately?’ I think in this changing economic climate, redesign is a key strategy for managing costs.”

Mary Tilton tried to educate shoppers a few days ago at a Sam’s Club in North Canton, about 50 miles south of Cleveland, luring shoppers with chocolate chip cookies and milk as she showed them how to pour from the new jugs.

“Just tilt it slowly and pour slowly,” Tilton said to passing customers as she added information about the jugs’ environmental and cost savings. Instead of picking up the jug, as most people tend to do, she kept it on a table and gently tipped it toward a cup.

Mike Compston, who owns a dairy in Yerington, Nev., described the pouring technique in a telephone interview as a “rock-and-pour instead of a lift-and-tip.”

The new jug marks a sharp break with the way dairies and grocers have traditionally produced and stocked milk.

Sam’s Club started rolling out the boxy jugs in November, and they are now in 189 stores scattered around the U.S. They will appear soon in more Sam’s Club stores and perhaps, eventually, in Wal-Marts.

Demonstrations are but one of several ways Sam’s Club is evangelizing the containers. Signs in the aisle laud their cost savings and “better fridge fit.”

Some customers have become converts. “With the new refrigerators with the shelf in the door, these fit nice,” said April Buchanan, who was shopping at the Sam’s Club in North Canton.

Others, even those who rue the day their tried-and-true jugs were replaced, praised the lower cost, $2.18 versus $2.58 a gallon.

The question now is whether customers will go along, learning all over again how to pour milk.