(NBC) - Hey America, want to save $13.8 billion over the next 30 years? Get rid of your dollars.

The greenbacks, that is. Let's use dollar coins instead.

That's the message from a consumer advocacy group and former presidential candidate, Sen. John McCain, who has re-introduced legislation to phase out dollar bills.

Eliminating the dollar bill in favor of the coin would save $13.8 billion over 30 years, says the consumer group Council for Citizens Against Government Waste (CCAGW). At a Capitol Hill briefing on Monday, the group said printing dollar bills may be cheaper than minting coins, but they last only about four years compared with 30 years for a coin.

The savings would nearly triple other recent estimates of the $1 coin's impact, said Aaron Klein, former chief economist for the Senate Banking Committee and Deputy Assistant Secretary of the U.S. Treasury, who conducted CCAGW's analysis on the savings potential.

"The federal government should always be looking for ways to save money, and as the national debt approaches $17 trillion, the implications of Mr. Klein's study amount to much more than pocket change," said Bill Christian, CCAGW's director of government affairs.

The Government Accountability Office, a bipartisan congressional watchdog, has produced five reports in the past 20 years to support the transition to $1 coins. Its last report, in 2011, said the government could save $5.5 billion, a conservative estimate according to advocates.

"It seems to me this one common-sense remedy certainly won't change the equation entirely. But even in this town, $5.5 billion or $13.8 billion is not chump change," said McCain, a Republican of Arizona.

McCain has been joined in his legislative push for the coins by fellow Republican senators Tom Coburn, of Oklahoma and Mike Enzi of Wyoming, as well as Democrats Mark Udall of Colorado and Tom Harkin of Iowa.

Americans have never warmed to dollar coins. The Susan B. Anthony and Sacagawea coins never became widely circulated and President Obama stopped production of presidential coins in December 2011 to reduce costs. Nearly $1.5 billion worth of the coins are stored with the Mint.