RESNET (Residential Energy Services Network) is a non-profit organization that aims to improve the energy efficiency of homes and buildings through the development of national standards and certifications. It is best known for the Home Energy Rating System (HERS) Index, which serves as a nationally recognized system for inspecting and calculating a home's energy performance. RESNET provides training and certification for HERS Raters and offers resources for homeowners, builders, and energy professionals to improve energy efficiency.