Wire Color Code
Black or red is hot, white is neutral, green is ground.
By Jonathan West · reviewed 2026-10-07 ·how we research these
In United States home wiring under the National Electrical Code (NEC), black and red wires are hot conductors, white or gray wires are neutral conductors, and bare copper or green wires are equipment grounds. A white wire is not guaranteed to be neutral in every situation, because switches and 240-volt circuits sometimes use a white conductor as a hot wire.
Wire color alone cannot confirm whether an electrical conductor carries voltage. Previous repairs, faded insulation, or altered connections can leave unexpected voltage on any conductor, so you must always turn off the circuit breaker and test each wire before touching it.
United States Household Wire Color Meanings
United States residential wiring follows national standards that identify conductor functions by insulation color. Under the National Electrical Code, published as NFPA 70 by the National Fire Protection Association, the color on a conductor tells you whether it carries current, returns current, or provides safety grounding.
The code sets strict requirements for grounded conductors and equipment grounding conductors, but it does not specify a single required color for hot conductors. A hot conductor cannot use white, gray, or green insulation. Black and red are standard practice for hot conductors in houses, while blue and yellow are often used for travelers, feeders, or larger systems.
Never assume a white wire is neutral. In switch loops and certain 240-volt circuits, a white wire can carry full voltage.
Wire Color Code Chart for Homes
This reference table lists the conductor insulation colors used in standard residential branch circuits. It outlines the role each color plays and highlights critical safety considerations.
| Color | System Role | Notes |
|---|---|---|
| Black | Ungrounded conductor (Hot) | Standard hot conductor in 120 V circuits, carries voltage from panel to load. |
| Red | Ungrounded conductor (Hot) | Common hot conductor in 240 V circuits, 3-way switches, and multi-wire branch circuits. |
| Blue or Yellow | Ungrounded conductor (Hot) | Often used for travelers, feeders, or larger systems, carries line voltage. |
| White or Gray | Grounded conductor (Neutral) | Returns current to panel, hot in switch loops and some 240 V cables where re-identified. |
| White with three stripes | Grounded conductor (Neutral) | Permitted by NEC Article 200 for grounded conductors. |
| Bare copper | Equipment grounding conductor | Directs fault currents to earth, permitted for equipment grounding under code. |
| Green or Green with yellow stripe | Equipment grounding conductor | Reserved under NEC 250.119 for equipment grounding, never used as hot or neutral. |
Switch Loops and 240-Volt Circuit Exceptions
A white wire does not always serve as a neutral conductor. In a two-wire switch loop, power travels down to a light switch and returns to the fixture through a cable that contains only one black wire and one white wire. The NEC allows the white conductor to serve as a hot wire in this configuration, but it must be permanently re-identified with black or red tape or paint at its terminations.
Standard 240-volt branch circuits use two hot conductors, commonly black and red, along with an equipment grounding conductor. A neutral wire is included only when an appliance, such as certain clothes dryers or cooking ranges, requires 120 volts for internal controls or clocks. A 240-volt-only circuit has no neutral, and any white conductor used as a hot wire in that cable must be permanently re-identified with tape or paint.
Wiring a clothes dryer, range, electric vehicle charger, or any 240-volt branch circuit requires a licensed electrician in most jurisdictions. Any work at the main electrical service panel is also work for a licensed electrician.
Device Terminal Screw Colors
Electrical devices such as receptacles and switches follow a terminal color convention that pairs with the conductor insulation colors. Connecting the correct conductor to its matching terminal screw maintains correct circuit polarity.
Standard duplex receptacles use brass-colored screws for hot conductors and silver-colored screws for neutral conductors. A green screw connects directly to the bare copper or green equipment grounding conductor. Standard wall switches use brass screws for the hot conductors. These color pairings follow widespread manufacturer conventions, but you must always read the manufacturer instructions included with the device before making connections.
Cable Jacket Colors Versus Wire Insulation Colors
The outer jacket of nonmetallic cable, commonly called NM-B or Romex, follows an outer color convention that indicates the wire gauge inside the sheath. Conductor insulation colors inside the cable remain black, white, and bare copper, regardless of the outer sheath color.
In modern nonmetallic cable, a white outer jacket contains 14 American Wire Gauge (AWG) conductors, a yellow outer jacket contains 12 AWG conductors, an orange outer jacket contains 10 AWG conductors, and a black outer jacket contains 8 AWG or 6 AWG conductors. These jacket colors represent the common US manufacturing convention, and the conductor gauge is also printed directly on the jacket. The circuit breaker in your service panel must match the smallest conductor gauge connected to the circuit. You can verify gauge requirements on our wire gauge chart.
Why Wire Colors Cannot Guarantee Safety
Color coding indicates intended function, but it does not guarantee that a wire is safe to touch. Previous property owners or unqualified installers may have wired connections incorrectly, mixed hot and neutral legs, or neglected to mark a re-identified white conductor.
Older homes present additional challenges. Older cloth-insulated wiring has no reliable color identification, and some older houses have no equipment grounding conductors present in the boxes. Insulation can also discolor or fade from age and heat over decades of service.
Always switch off the circuit breaker at the electrical panel before opening any electrical box. Never rely on color to decide if a wire carries current. Test the circuit first with a non-contact voltage tester, and confirm your tester functions properly on a known live circuit before using it. Verify zero voltage between hot, neutral, and ground using a tool shown in our guide on how to use a multimeter.
Thermostat Low-Voltage Wire Colors
Heating and cooling systems use low-voltage control wiring that operates at 24 volts, which carries far less shock risk than 120-volt or 240-volt household wiring. You must still switch off power at the furnace or air handler before handling these wires to avoid shorting out the equipment control board.
Thermostat wiring follows a general trade convention rather than an enforceable color standard. Red typically provides 24-volt power to the R terminal, white connects to heating at the W terminal, yellow controls cooling at the Y terminal, green operates the indoor fan at the G terminal, and blue or black serves as the common wire at the C terminal. Because these colors are not standardized across all equipment, review our instructions on how to install a thermostat, examine the terminal labels on your furnace control board, and photograph existing wiring before disconnecting any lead.
International and Non-Residential Wiring Systems
Color standards differ outside the United States. In the United Kingdom and across the European Union, harmonized fixed wiring uses brown for live, blue for neutral, and green-and-yellow stripes for earth grounding. Australia and other countries enforce their own electrical codes and color requirements. United States rules do not apply to installations in those regions.
Direct current systems, electronic circuits, and automotive wiring do not follow residential AC rules. Automotive wire color systems vary by vehicle manufacturer and model year, and those systems fall outside the scope of home electrical standards.
When to Call a Licensed Electrician
Certain electrical situations require professional intervention. Call a licensed electrician for any work inside the main service panel, any meter base repairs, and any work involving 240-volt circuits. You should also call an electrician if your home contains aluminum wiring, active knob-and-tube wiring, or cloth-sheathed conductors without grounding.
Stop work and contact a professional immediately if you find wires that do not match recognizable color patterns, discover burn marks inside an electrical box, detect a burning odor, or feel an electrical tingle when touching a metal switch plate or junction box.
- Work inside the main electrical service panel or meter enclosure.
- Installing or modifying 240-volt circuits for appliances or equipment.
- Homes with aluminum branch wiring or cloth-insulated knob-and-tube wiring.
- Junction boxes that lack an equipment grounding conductor.
- Signs of heat damage, scorched insulation, or burning smells near wiring.
- Any electrical installation where you are uncertain of circuit connections.
Common questions
What color is the hot wire in a house?
In standard US residential wiring, black and red wires are hot conductors. The National Electrical Code permits other colors such as blue and yellow for hot conductors, but a hot wire can never use white, gray, or green insulation.
What color is the neutral wire?
The neutral wire, known in the code as the grounded conductor, is white or gray, or another color with three continuous white stripes. In typical household cables, the white wire serves this function except where it is re-identified as hot.
What does it mean if a box has both black and red wires?
Both black and red wires are hot conductors. They commonly appear together in 240-volt appliance circuits, multi-wire branch circuits sharing a neutral, or multi-way lighting circuits using travelers.
What color is the ground wire in household wiring?
The equipment grounding conductor is either bare copper, insulated in solid green, or green with a yellow stripe. Under NEC section 250.119, green and green with yellow stripes are identified specifically for grounding.
Can a white wire ever be used as a hot wire?
Yes. The NEC allows a white wire to serve as a hot conductor in certain switch loops and 240-volt cable assemblies, but it must be permanently re-identified with black or red tape or paint at every termination point.
What do wire colors mean in the UK and Europe?
In harmonized UK and European wiring, brown is the live conductor, blue is the neutral conductor, and green-and-yellow striped is the earth ground conductor. These systems differ entirely from US residential wiring standards.