Hagel included the cost in a report sent to the House Armed Services Committee, and two top Senate Democrats -- Majority Whip Dick Durbin of Illinois and Dianne Feinstein of California -- announced the figure at a Senate Judiciary Committee subcommittee hearing, The Hill reported.
The Hill said it had obtained the report on Guantanamo operating costs that Hagel had provided to Rep. Adam Smith, D-Wash., the ranking Democrat on the House Armed Services Committee. The Hill said the Pentagon report concluded the United State has spent $4.7 billion to operate the detainee facility since 2002.
"This is a massive waste of money," said Feinstein, who chairs the Senate Intelligence Committee.
The Subcommittee on the Constitution, Civil Rights and Human Rights hearing -- the first since 2009 on closing the facility -- came two months after President Barack Obama announced new steps concerning the closure of Guantanamo.
Durbin said in a release the hearing would take testimony on the indefinite detention of 166 remaining detainees, including 86 detainees who have been cleared for transfer.
"The president has called for the closing of the Guantanamo detention facility and many in Congress support him," Durbin said. "But Congress and the administration have been complicit in the current situation which harms our national security and leaves more than 150 detainees in limbo.
"We need to address the future of the prison swiftly and decisively. This hearing will be the first step toward putting this dark period behind us once and for all."
Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., said it was "shameful" Congress is still debating the matter.
"For over a decade, the indefinite detention of prisoners at Guantanamo has contradicted our most basic principles of justice, degraded our international standing and, by itself, has harmed our national security," he said.
Durbin said at Wednesday's hearing the cost-per-detainee at Guantanamo -- $2.7 million per year, compared to $78,000 at "supermax" prisons -- "would be fiscally irresponsible during normal economic times, but it is even worse when the Defense Department is struggling to deal with the impact of sequestration."
Sen. Ted Cruz, R-Texas, the ranking Republican on the subcommittee, said Guantanamo is the only facility that can hold "terrorists who would work night and day to murder innocent Americans."