Electrical wiring is the network of conductors that distributes electricity through a building. It runs from the service entrance, through panels and subpanels, to outlets, switches, lights, and equipment. Wiring is hidden inside walls and ceilings, but it is the nervous system of any modern building.

Wiring must be sized correctly. Wire gauge determines how much current it can carry safely. Too small a wire for the load, and it overheats — a fire risk. Circuit breakers and fuses protect against overloads and short circuits. Grounding provides a safe path for fault current.

Codes regulate wiring in detail. The National Electrical Code in the United States sets standards for installation, materials, and protection. Inspectors check wiring before walls are closed up, because mistakes are hard to find later.

Modern buildings also include low-voltage wiring for data, security, and controls. These systems often share pathways with power wiring but must be kept separate to avoid interference.