The United States’ energy system, vast in size and increasingly complex, is the engine of the economy. The national energy enterprise has served us well, driving unprecedented economic growth and prosperity and supporting our national security. The U.S. energy system is entering a period of unprecedented change; new technologies, new requirements, and new vulnerabilities are transforming the system. The challenge is to transition to energy systems and technologies that simultaneously address the Nation’s most fundamental needs—energy security, economic competitiveness, and environmental responsibility—while providing better energy services.

The introductory chapter of the 2015 Quadrennial Technology Review frames these energy challenges and the R&D opportunities, explored in the remainder of the report. It summarizes the state of the system, recent changes, and strategic objectives.