Cash costs Americans $200 billion a year - CNBC

The study found that getting paid electronically (either through direct deposit or a payroll card) is often significantly cheaper than receiving a paper check if there are check-cashing fees (for the unbanked).

Who has the cash?

Most of us have some cash on hand, but that amount varies by income and key demographic factors. Here are some key findings from the study:

• Those in households with income of $20,000 to $100,000 a year usually have less than $100 in cash.
• Those under 35 have median cash balances roughly half the size of those over 55, but they pay more in fees than older people.
• Men carry nearly double the amount of cash women do. Men are also slightly more likely than women to always keep some cash on hand. This might explain why men use roughly 50 percent more cash each month than women.
• The self-employed and those who hold multiple jobs have the greatest cash balances.
• Latinos, Pacific Islanders and Native Americans report much higher average cash holdings than white, African-American and, in particular, Asian-Americans.

Is there a lesson here?

Benjamin Mazzotta, a research fellow at Tufts who co-authored this study, believes it has important public policy implications. They include if something should be done to help people on fixed incomes, or those who don't have or want a bank account but need a modern, cost-effective way to pay for things.

(Read more:Employers can't force debit cards on their workers)

"Why shouldn't they have access to reliable, cheap, universally accepted payment instruments like the ones you and I use and take for granted every day, like debit and credit cards and direct deposit?" Mazzotta asked.

The National Consumer Law Center, an advocacy group for lower-income and other disadvantaged Americans, agrees that it's important to give people access to electronic payments, so they don't have to rely on cash. But staff attorney Lauren Saunders isn't convinced that all the new systems are superior to cash, which is so easy to use.

"In the financial world, there are costs to everything," Saunders said.

(Read more: How to complain about your bank)

The center wants people to have access to both cash and electronic payments, whatever works for them.

"We shouldn't discourage cash and push everybody to electronic payments, because a lot of that is being driven by industry looking for ways to get their two cents out of it, to earn fees that you don't get when people pay with cash," she said. "Cash is still very useful."

—By CNBC contributor Herb Weisbaum. Follow him on Facebook and Twitter@TheConsumermanor visit The ConsumerMan website.

Correction:

This story has been updated to correct the cash figure in the headline.