Energy bandwidth studies can serve as foundational references in framing the range (or bandwidth) of potential energy savings opportunities in U.S. manufacturing. This bandwidth study is one of a series of six energy bandwidth studies on lightweight structural materials manufacturing. The study examines energy consumption and potential energy savings opportunities in U.S. glass fiber reinforced polymer composites manufacturing. The study relies on multiple sources to estimate the energy used in the manufacturing of the lightweight material for four application areas (automotive, wind energy, aerospace, and pressure vessels), accounting for approximately 47% of overall U.S. glass fiber production in 2010. Energy savings opportunities for the six manufacturing sub-processes studied are based on technologies currently in use or under development.