By Karen Fernau
The Arizona Republic

More and more, cooking is about saving time.

We buy bagged salads, cooked sausage and boxed lasagna kits. A huge selection of convenience foods makes it easier than ever to save time and energy in the kitchen.

WHAT IT COSTS

The extra cost of a bag of washed, packaged lettuce might not seem like much. But if you eat 30 bags a year, it adds up. Here is what Arizona State researchers determined the per-hour cost you would pay to have convenience products made for you: Shredded Cheddar cheese: $80 Sliced Gala apple: $74.84 Pre-cut celery: $49.22 Boxed lunch kit (Lunchables): $20.06 Washed and bagged romaine lettuce: $13.50 Pre-cut watermelon: $6.12 Frozen bacon-and-egg breakfast: $5.18 Frozen chicken teriyaki: $4.26 Frozen pancakes: $2.97 Pre-cut broccoli: $1.80 Tuna lunch kit: 77 cents Frozen beef stew: 12 cents

Such a deal, right? The answer: yes, and no. These products almost always save time, but convenience has its price.

"I really don't think the consumer thinks much about what they're paying for convenience, and they really should. It can be expensive," says Linda Vaughan, chairwoman of Arizona State University's Department of Nutrition.

If you buy sliced apples, for example, you're paying $74.84 an hour for someone else to do the work.

And if you buy cooked frozen sausage, we have bad news: You'll pay more, but it takes the same amount of time to cook as fresh sausage.

On the flip side, bagged lettuce is a pretty good deal. So are those time-saving tuna lunch kits packed with fish, mayo, relish and crackers - the cost is about the same as if you bought the ingredients separately.

19 products tested

Vaughan recently led student researchers in a series of experiments to determine the money spent on and time saved by convenience foods. Arizona State testers timed the preparation of 19 convenience products, including kids' snacks, bagged produce, meals-in-a-box and frozen pancakes. Testers then clocked the time it takes to make the same item from scratch. The differences in time and the cost of the food revealed exactly how much time is actually saved vs. how much consumers pay.

The results are mixed, but they raise the question: Can convenience cost too much?

Perhaps not. Time-stressed shoppers say they are willing to pay as much as three times more for convenient versions of their favorite food, according to a survey by Information Resources Inc., a Chicago company that tracks consumer spending.

Industry observers wonder whether shoppers are doing the math.

Consumers know they pay "something" for convenience products, but "would rather spend the money than the time," says Stephanie Childs, spokeswoman for the Grocery Manufacturers of America. "Consumers are buying whatever helps them put a meal on the table fast. We Americans are busy."

High exhaustion rate

Consider U.S. Labor Department statistics: More than 47 million women are working full time. One in four of these women are working more than 40 hours a week. Forty-four percent of all workers come home exhausted.

As a result, nearly 75 percent of consumers recently surveyed by the Food Marketing Institute say they serve home-cooked meals three or more times a week, but fewer than half prepare complete meals from scratch