On the mainstage of VERGE 19, Joel Makower discuss energy efficiency with Amory Lovins, Cofounder and Chief Scientist of the Rocky Mountain Institute. Energy efficiency, a bigger energy “source” than oil, avoids at least twice as much global greenhouse gas emissions as renewables’ remarkable growth. Yet its potential is far larger. Designing buildings, vehicles, and factories as whole systems can save many times more energy than previously thought, and often at lower cost. Systems thinking can also save most of the energy-intensive activities and materials (like steel and cement) often considered hardest to decarbonize.