A power outage (or blackout) is the complete loss of electrical supply, often triggered by severe weather, earthquakes, equipment failure, or grid overload. Outages range from brief transient faults and voltage drops (brownouts) to severe, long-lasting blackouts, as well as rolling blackouts used when demand exceeds supply. Critical facilities like hospitals and telephone exchanges rely on backup generators and lead-acid battery rooms to maintain safety and communication during these events. Notable examples include the California electricity crisis of 2000–2001 and the 2019 California power shutoffs, which were implemented to prevent wildfires from faulty transmission lines. To prevent damage, power grids must balance generation and load every second, using protective relays to avoid cascading failures, though modern systems build in redundancy to resist large-scale collapses.