Energy efficiency supports the reliability and resilience of our electricity system. However, these benefits are typically not included in electric system planning, decision making, and cost-effectiveness analysis. This report examines energy efficiency's contribution to reliability in terms of electricity supply, transmission and distribution infrastructure, and wholesale power markets. Efficiency's benefits include supporting system reserve margins and functioning as a nonwires alternative to address grid congestion. Drawing lessons from a number of case studies, the report concludes with recommendations to help policymakers and stakeholders capture the full range of efficiency's reliability benefits.