House Electrical Wiring: What You Need to Know

Updated: Dec. 03, 2023

Before you take on your next home wiring project, arm yourself with basic information about the electrical cable and wiring that you’re likely to see.

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wire electrical cable basics
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Electrical Cable Types: The Basics

The wire and cable aisle at your home center can be a pretty confusing place. We’ll teach you how to identify different electrical wire types and their uses, and how to determine the size of individual wires and their purposes. You’ll be able to cut through the confusion, get exactly what you need and ensure that your wiring is safe.

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wire cutters
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Electrical Wire vs. Electrical Cable

People often use these terms interchangeably, but there’s a difference:

  • A cable assembles two or more wires in a single jacket.
  • Wires are the individual insulated or bare conductors inside the jacket.
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wire sizes gauge

Wire Gauge

Wires come in different sizes/gauges to work with the amperage of the circuit in which they’re used. It’s counterintuitive, but the larger the number, the smaller the wire.

The most common work gauge sizes you’ll find in residential work are 14-gauge and 12-gauge. Larger appliances such as electric stoves, electric water heaters, electric dryers and central air units will often use 10-, 8- or even 6-gauge wire.

If you’re adding an outlet, you need to use wire that’s the same gauge as the existing wiring. How do you tell your old wiring gauge? Here’s a simple visual.

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cable by the numbers
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Cable by the Numbers

An electrical cable is classified by two numbers separated by a hyphen, such as 14-2. The first number denotes the conductor’s gauge; the second denotes the number of conductors inside the cable.

For instance, 14-2 has two 14-gauge conductors: a hot and a neutral. This cable also contains a bare copper wire as the ground. Individual conductors are also color-coded, which tells you their purpose in the circuit.

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cables outer sheath color coding

Outer Sheath Color Coding

The color of a cable’s outer sheath tells you the gauge of the wire inside the sheath as well as the amperage rating for the circuit.

WHITE = 14-gauge wire, 15-amp circuit

YELLOW = 12-gauge wire, 20-amp circuit

ORANGE = 10-gauge wire, 30-amp circuit

BLACK = 8- or 6-gauge wire, 45- or 60-amp circuits. Check sheath labeling for gauge and circuit specifics.

GRAY = Underground cable. Since all UF (underground feeder) cable is gray, check the sheath labeling for gauge and circuit specifics.

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Cords, Chargers and Cables
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Not All Cable Is Color-Coded

Cable-sheath color coding started in 2001 and is still voluntary. If you have older wiring, don’t assume it complies with the current color coding. However, most manufacturers now follow the standard color code.

Wiring problems and mistakes are all too common, and if left uncorrected have the potential to cause short circuits, shocks and even fires. Planning to buy smart devices? Here’s what you need to know about smart home wiring.

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wire color coding

Wire Color Coding

This code is standard for all conductors. The colors you’re most likely to find in your home are the following:

BLACK (OR RED) = HOT. Hot wires carry current from the panel to the device, which could be a switch, receptacle, light fixture or appliance. There are other colors for hot wires, but they’re much less common.

WHITE = NEUTRAL. Neutral wires carry the current back to the panel, completing the circuit.

BARE (OR GREEN) = GROUND. In the event of a ground fault, the ground wire provides a path for the fault current to return to the panel, opening the breaker or blowing the fuse and cutting off the flow of electricity.

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nonmetallic cable

NM-B – Nonmetallic Cable

This is the most common type of electrical cable in homes built since the mid-’60s. “Nonmetallic” simply means that the outer jacket is not metal. It’s often referred to as Romex, which is a brand name. Typically, NM-B cable has either two conductors and a ground, or three conductors and a ground. The conductors are individually insulated, wrapped in paper and sheathed in plastic. Ground wires are either bare copper or insulated in green.

14-2 Used for general lighting and receptacle circuits. 15-amp circuit maximum.

14-3 Used for three-way switches and split receptacle circuits. 15-amp circuit maximum.

12-2 Used for 20-amp kitchen, bathroom, laundry and garage receptacles; 230-volt heating circuits up to 3,700 watts; and 115-volt circuits up to 1,800 watts. Can be used anywhere in place of 14-2.

12-3 Same uses as 12-2, with the addition of three-way switches and split receptacle circuits.

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underground feeder cable
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UF – Underground Feeder Cable

UF is used primarily to bring power to detached garages, outbuildings or outdoor lighting. The insulated conductors are molded into the sheathing. Depending on the situation, UF is either direct-buried or run in conduit. It must be protected from physical damage by conduit where it exits the ground and is exposed. Understand wiring color codes so you can finish the job safely.

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metal-clad cable
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MC – Metal-Clad Cable

MC cable is common in unfinished areas where the cable would otherwise be exposed and subject to physical damage. It’s also sometimes used inside walls. A bare aluminum wire is in continuous contact with the metal sheathing. The combination of aluminum wire, sheathing and metal boxes grounds the circuit.

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stranded wire vs solid wire

Stranded Wire vs. Solid

Stranded wire is more flexible than solid. If you’re pulling wire through conduit, stranded wire makes it easier to get around corners and bends in the conduit. However, if the situation requires pushing wires through a conduit, you’ll want to use solid wire.

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Types Of Electrical Wires Common Specialty Cables For Electrical Wiring
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Common Specialty Cables for Electrical Wiring 8

Here’s a list of other specialty cables and wires you’ll find at home centers and hardware stores:

  • Type SE Cable (service-entrance cable)
    • Type SE cable is similar to Type NM-B cable because it’s a factory assembly of insulated wires and a grounding wire. Type SE cables have a flame-retardant and moisture-resistant nonmetallic sheath. It’s often used as a substitute for Type NM-B cable for electric ranges, electric clothes dryers, air conditioning units and similar large appliances and equipment. It’s also a popular option if you need to install a feeder circuit from your main service panel to a sub-panel.
  • Type USE Cable (underground service-entrance)
    • Type USE can be individual wires or a multi-conductor cable. It cannot be used for interior wiring because it lacks flame-retardant properties. It’s intended for outdoor use. It would be a good option for running power to a large detached shop building. Here are a few ways to run an outdoor electrical wire.
  • Mobile home feeder cable
    • This is a convenient assembly of four wires for supplying 100 amps of power to a mobile or manufactured home. It’s labeled as “2-2-2-4 Aluminum Mobile Home Feeder.” Translation: It consists of two #2 AWG hot wires, one #2 AWG Neutral wire and one #4 AWG ground wire. This assembly lacks an overall outer sheath because the wires are approved for direct burial in the earth. The four wires are twisted together at the factory for ease of installation in the field.
  • Twisted well pump cable
    • This is another convenient assembly of wires without an overall plastic sheath, approved for direct burial to supply power for submersible well water pumps at residential and farm properties. The individual insulated wires are similar to Type USE wires and can withstand harsh underground conditions. It’s available in lots of sizes depending on the installation requirements.
  • URD cable (underground rural distribution)
    • This is a classification of large cables used for distributing electrical power. This would be a good option for distributing electrical power to multiple buildings on a single property, such as a home, a shed, a storage building and so on. It’s often labeled as “2/2/4 Aluminum URD.” Translation: The factory assembly consists of two #2 AWG hot wires and one #4 Neutral wire. This particular example does not have a ground wire. However, this cable assembly is available in many configurations and sizes, with or without a ground wire.
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Types Of Electrical Wires Common Specialty Cables For Low Voltage Wiring
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Common Specialty Cables for Low-Voltage Wiring 9

  • Landscape lighting cable
    • This is used for low-voltage outdoor lighting for landscaping, accent or security lighting. It’s approved for outdoor use, suitable for direct burial and is sunlight resistant.
  • Thermostat cable
    • This is used for thermostat wiring and other similar types of control wiring. It’s available in lots of sizes and configurations. It’s also used for doorbell wiring. This cable is approved for in-wall use. It will often be labeled as Type CL2 (Class 2 Circuits).
  • Audio cable
    • This is a power-limited circuit and communications cable for whole-house audio systems. It’s approved for in-wall use. It will often be labeled as Type CL2 (Class 2 Circuits) or CM (Communication Circuits).
  • Security system cable
    • Similar to an audio cable, it’s a power-limited circuit cable intended for whole-house security systems. It’s approved for in-wall use. It will often be labeled as Type CL2 (Class 2 Circuits), Type CL3 (Class 3 Circuits), CMR (Communication Riser), or Type FPLR (Fire Power Limited Riser). It’s a multipurpose low-voltage cable.

Types Of Electrical Wires Common Specialty Cables For Low Voltage Wiring
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  • Speaker wire
    • This is the transparent wire we use for connecting speakers and woofers to our audio equipment or audio system wall jacks. Beware: This type of speaker wire is NOT approved for in-wall use.
  • Computer network cable
    • CAT 5E and CAT 6 computer network cables are used for high-speed data transmission for computers, modems, routers, printers and similar equipment connected to a data network. These ethernet cables are approved for in-wall use. They do not come from the factory with pre-installed connectors. This type of cable needs to be terminated at wall jacks or crimped connectors. These cables contain the familiar grouping of four twisted pairs of wires. They will often be labeled as Type CM (Communication), Type CMR (Communication Riser), or CMP (Communication Plenum). Lots of types and configurations are available. Beware: Ethernet cables with pre-assembled, factory-installed connectors are usually not rated for in-wall use. They’re intended for interconnecting computer equipment in a room, not permanently installed inside walls, floors, and ceilings.
  • Coaxial cable
    • This is often referred to as “RG6″ cable. It’s used for video signals, closed-circuit TV and broadband internet access. Approved for in-wall use, this cable usually has several layers of shielding to eliminate electronic interference from nearby electrical sources. It’s often labeled as Type CM (Communication), CL2 (Class 2 Circuits) or Type CATV.
  • Telephone cable
    • Yes, in the modern era of cellphones you can still buy telephone cable for installing landline phones. This type of cable is approved for in-wall use. The round cable consists of four 24 AWG wires. It’s typically labeled as Type CM (Communication) and is not a substitute for ethernet cable.