Energy Efficient is the 14th track of the second disc of the Halo Wars 2: Original Soundtrack.
MJOLNIR Mix • Blow Me Away • Peril • Ghosts of Reach • 1st Movement of The Odyssey • Heretic, Hero • Flawed Legacy • Impend • Never Surrender • Ancient Machine • 2nd Movement of the Odyssey • In Amber Clad • The Last Spartan •