Story updated at 10:05 a.m. EDT to include comment from DOE.

Republicans on the House Energy and Commerce Committee have asked U.S. EPA and the Department of Energy to explain billions of dollars that sometimes remain unspent by the agencies at the end of each fiscal year.

The request -- sent in letters to the agencies Monday -- is the latest in Republicans' review of federal budgets to highlight their policy disagreements with the White House. Committee Chairman Fred Upton (R-Mich.) and Oversight and Investigations Subcommittee Chairman Cliff Stearns (R-Fla.) have held several hearings as part of a planned series on cutting agency spending.

The latest letters ask DOE, EPA, the Department of Commerce and the Department of Health and Human Services to list the unexpended balances that will be carried over into fiscal 2012, provide details on the funds carried over from fiscal 2009 and describe all instances when such unobligated funds have offset budget requests to Congress. The agencies have until Nov. 7 to reply.

"The information committee members are seeking is crucial as each government agency will deliver its annual budget request early next year," the Energy and Commerce Committee's Republicans wrote in a news release. "It has become common for agencies to put forth annual budgets without a detailed disclosure of how much federal funding remains from prior appropriations."

Citing data from the Office of Management and Budget, the lawmakers say that DOE had more than $47 billion in obligated balances at the end of fiscal 2010 and more than $8 billion in unobligated funds. EPA had more than $13 billion in obligated balances and more than $4 billion in unobligated funds.

Obligated balances mean the funding is earmarked for a purpose but unspent; unobligated funds have not yet been allocated. A Government Accountability Office report found that some agencies do not report those numbers, and Republicans say the funds could help offset new funding as Congress looks to cut government spending.

A spokesman from EPA did not immediately respond to a request for comment, nor did Democrats on the Energy and Commerce Committee. DOE spokesman Damien LaVera said agency officials "look forward to reviewing the letter and working with the committee to provide them the information they need."

At a hearing earlier this month, EPA Chief Financial Officer Barbara Bennett said such unobligated funds are never drawn from the Treasury. Typically meant for ongoing or delayed projects that might still need it, she said EPA eventually clears the appropriations from its balance sheet (E&ENews PM, Oct. 12).

Click here for the letters to DOE, EPA, HHS and Commerce.