Funny, as it actually turned out, energy efficiency research for both electricity and transportation has worked very well, as have wind turbines and solar power. And quite a bit of that comes from DOE research.
Fusion reactor? Well, that's still 30 years away.
Of course the vast majority of DOE money is devoted to the nuclear weapons infrastructure and environmental cleanup from decades of nuclear weapon infrastructure.
For instance, take the FY 2012 budget of Los Alamos National lab.
What fraction would you say is on basic science? I expected 30%. More like 4%.
57% NNSA weapons
9% NNSA nonproliferation
7% NNSA 'safeguards and security'
7% work for national security (most likely intelligence agencies)
8% environmental cleanup
4% undefined 'work for others'
4% DOE Energy and Other Programs
4% DOE Office Of Science