Main breaker
The large double-width switch at the top of your panel that cuts power to the whole house at once.
The main breaker is the single oversized switch — usually at the very top or bottom of your [service panel](/glossary/service-panel) and labeled with an amp rating like 100, 150, or 200 — that controls all the power feeding your home. Flipping it OFF de-energizes every circuit at once, which is what you want before a flood reaches outlets or when an electrical emergency forces you to kill power fast. Safety guidance is to switch off the individual branch breakers first, then the main, and to reverse the order (main first, then branches) when restoring power. Know where yours is and that you can reach it without standing in water — see [how to shut off your utilities in an emergency](/guides/how-to-shut-off-utilities-in-an-emergency).