What causes a partial blackout?

A partial blackout affecting only specific rooms, appliances, or one side of a house while other areas retain full electrical power is typically caused by one of several distinct electrical issues. Common causes include a tripped upstream Ground Fault Circuit Interrupter (GFCI) receptacle, a loose wire nut or terminal connection inside a junction box, a tripped double-pole breaker where only one internal pole opened, or a dropped neutral or hot line from the utility company's overhead or underground service drop. When an incoming utility line fails, half of your home's 120-volt circuits lose voltage entirely. You can troubleshoot partial power loss safely by checking your service panel layout and observing neighboring homes. You can verify that your corrective action is successful when resetting tripped breakers, securing loose junction box connections, or contacting your electric utility company to repair a dropped service line restores full electrical power to the affected rooms.