If we completely scrapped the DoE and put the annual appropriation into buying oil each year (at $100/bbl), we would have 6.6 million barrels of oil each day.
The NNSA is a part of the DOE. The NNSA (National Nuclear Security Administration) designs and maintains the nuclear arsenal. We really ought to keep those guys around.
The rest of the DOE is unnecessary as far as I can tell.
That puts it into perspective.