Manufactured homes are an important source of affordable housing for nearly seven million Americans, particularly low-income residents. Unfortunately, energy efficiency in manufactured homes lags behind that of site-built homes. This study examines the potential for and benefits of energy efficiency in manufactured homes. It assesses the current housing market, characterizes energy use, and analyzes the cost-effective potential for energy efficiency improvements throughout the manufactured housing sector. Results highlight substantial potential for programs and policies to mobilize energy efficiency in manufactured homes.