It Costs a Lot When the Kids Move Back In

NEW YORK ( TheStreet) -- So you're looking to save on some household bills?

There are many ways to do that, starting with cutting your cable bill, reducing your mortgage rate with a refinancing deal or even moving to a smaller house.

But one surefire way to make your household budget balloon right back up again is to invite an adult child to move back into your house.

Sure, you may not have much of a choice. According to Gallup 28.4% of Americans in the 18-to-29 age group were "underemployed" as of July 31.

That's triggered a prodigal son-and-daughter return to the nest for almost 22 million American young adults, according to the Pew Research Center and Securian Financial Group, or about 36% of all U.S. young adults between the ages of 18 and 31.

"Most of these young adults are in the dark about the effect they have on their parents' finances," says Michelle Hall, a market research manager at Securian Financial Group. "Nearly 45% say their living at home has no financial impact. Yet elsewhere in the survey, nearly half (44%) of those same people said they are unsure of the impact. They simply do not know how living at home affects their parents financially."

The study points out that only 10% of young adults living at home pay rent, although 49% say they help with some household expenses, such as utility or cable bills. In addition, the study reports that "parents not only keep their adult children living at home in the dark about their finances, few parents make financial demands on them."

A separate study from the National Endowment for Financial Education says that 25% of parents with adult children under the same roof go into debt, while 60% of U.S. parents are "financially supporting" their adult children.

In addition, NEFE says that 13% of parents put off buying a new home, and 7% delayed retirement to help their adults sons and daughters out financially.