Residential wiring follows NEC (National Electrical Code) standards that specify minimum wire sizes for different circuit types. Most homes use three main wire gauges: 14 AWG for 15A lighting circuits, 12 AWG for 20A outlet circuits, and 10 AWG for 30A dedicated circuits.
General lighting circuits use 14 AWG wire on 15A breakers. Standard outlet circuits use 12 AWG wire on 20A breakers. Kitchen countertop, bathroom, garage, and outdoor outlets require 20A circuits (12 AWG) per NEC. Dedicated appliance circuits (dryers, ranges, water heaters) use larger wire — typically 10 AWG for 30A, 8 AWG for 40A, or 6 AWG for 50A.
The main service entrance cable connects the utility meter to the main breaker panel. Common sizes: 100A service uses 4 AWG copper or 2 AWG aluminum; 200A service uses 2/0 AWG copper or 4/0 AWG aluminum. Most modern homes are wired for 200A service.
NM-B (Romex) is the standard for interior residential wiring — a non-metallic sheathed cable with two or three conductors plus ground. UF-B is rated for underground/outdoor use. THHN/THWN is used in conduit. MC cable (metal-clad) is used where additional protection is needed.
All residential circuits require an equipment grounding conductor. NM-B cable includes a bare copper ground wire. The ground wire is the same gauge as the circuit conductors (14 AWG ground on 15A circuits, 12 AWG on 20A circuits). The main grounding electrode conductor to ground rods is typically 6 AWG copper.
Disclaimer: This guide is for informational purposes only. Always consult a licensed electrician and follow local building codes for actual installations. Wire sizing depends on specific conditions including ambient temperature, conduit fill, and derating factors.