The Energy function covers the Department of Energy's non-weapons work — about $51 billion in FY2024. The biggest buckets are energy programs (renewables, grid modernization, nuclear power R&D — ~$25B), environmental management (cleanup of Cold War-era nuclear weapons sites like Hanford and Savannah River — ~$9B), and the Strategic Petroleum Reserve operations.
DOE runs almost all of its 17 national labs through Management & Operations contracts with non-profit, university, and industry consortia. Battelle Memorial Institute is the largest single operator (Pacific Northwest, Idaho, co-ops Oak Ridge and Brookhaven). Bechtel National runs the Hanford Waste Treatment Plant and partners on Lawrence Livermore. The University of California operates Berkeley Lab and co-operates LLNL. UChicago runs Argonne. UT-Battelle runs Oak Ridge.
A growing slice (~$5B+) flows as loans and grants to private clean-energy manufacturers under the Inflation Reduction Act and the DOE Loan Programs Office — Ford BlueOval City, Tesla Nevada, GM Ultium battery joint ventures, plus utility-scale solar, offshore wind, and hydrogen hub awards.