States invest in energy efficiency largely because it is a low-cost resource that can displace the need for traditional supply-side investments including electricity generation and transmission and distribution (T&D). Regulators and utilities account for costs and benefits using cost-effectiveness tests that inform utility and regulatory decision making about system operation and new resource investments. Synapse Energy Economics compiled the DSESP based on research on state practices as well as surveys and interviews with state agency staff, program administrators, and other stakeholders. This tool can help states answer questions like “How do our practices compare to other states?” and “What can we learn from other state practices?” The DSESP also features a list of guidance documents to inform state efforts in estimating a range of utility and non-utility energy efficiency system impacts. This topic brief highlights how the DSESP can advance energy efficiency as a resource and help states implement appropriate cost-effectiveness strategies.