The provision of reliable, secure, and affordable electricity is essential to power economic growth and development. The power system is at risk from an array of natural, technological, and man-made threats that can cause everything from power interruption to chronic undersupply. It is critical for policymakers, planners, and system operators to safeguard their systems and plan for and invest in the improved resilience of the power sector in their countries. Through holistic resilience planning, actors can anticipate, prepare for, and adapt to the threats and stresses on the power system. Resilience planning identifies the threats, impacts, and vulnerabilities to the power system, and devises strategies to mitigate them. What are threats to the power system? Power sector vulnerabilities-weaknesses within infrastructure, systems, or operationsare susceptible to natural, technological, and human-caused threats. Impacts from these threats include potential fuel supply shortages for transportation and energy generation, physical infrastructure damage, shifts in energy demand, and disruption of electricity supply to the end user. 2 These disruptions, in turn, adversely affect critical services and facilities (e.g., hospital services, water treatment, and communications networks). As such, it is vital to understand threats to the power system and their associated impacts. NREL/TP-7A40-73618 | May 2019 NREL prints on paper that contains recycled content.