Behind the walls of every home runs a network of wiring that powers your lights, outlets, and appliances. Knowing the common types of electrical cables helps you understand what an electrician is talking about, plan a renovation budget, and recognize the right product when you see it on a job. That said, this guide is for understanding only. Electrical wiring must be installed by a licensed electrician to current National Electrical Code (NEC) requirements, with proper permits and inspections, and you should never work on live circuits.
Below is a plain-language overview of the cable and wire types you are most likely to encounter in residential and light commercial settings, along with their typical uses.
- Cable Versus Wire
- NM Cable (Romex)
- UF Cable (Underground Feeder)
- THHN and THWN Wire
- Metal-Clad and Armored Cable (MC and AC)
- Service Entrance Cable (SE and USE)
- Low-Voltage and Specialty Cables
- Understanding Wire Gauge
- Color Coding of Conductors
- Choosing the Right Cable for the Job
- Why You Must Hire a Licensed Electrician
- Final Thoughts
Cable Versus Wire
People often use the terms interchangeably, but there is a distinction. A wire is a single conductor, usually copper or aluminum, that may be solid or stranded. A cable is two or more wires bundled together inside a protective jacket. Most of the products below are technically cables because they group multiple conductors for a complete circuit.
NM Cable (Romex)
Non-metallic sheathed cable, commonly known by the brand name Romex, is the workhorse of modern residential wiring. It bundles two or more insulated conductors plus a bare ground wire inside a flexible plastic jacket. NM cable is used for most interior branch circuits, including outlets, switches, and lighting, in dry, protected locations inside walls and ceilings.
The jacket is color-coded by wire gauge in many products, for example white for 14-gauge and yellow for 12-gauge, which corresponds to the circuit’s amperage rating. NM cable is not rated for wet or exposed outdoor use.
UF Cable (Underground Feeder)
Underground feeder cable looks similar to NM but is built to be moisture-resistant and direct-burial rated. The conductors are embedded in solid, water-resistant insulation rather than loosely jacketed. UF cable is used for outdoor circuits and runs that go underground to detached garages, outdoor lighting, sheds, and pumps. It can be buried directly in the ground at the depth required by code.
THHN and THWN Wire
THHN and THWN are individual insulated conductors, not bundled cables, identified by their insulation type. These single wires are pulled through conduit, the rigid or flexible tubing that protects wiring in exposed or industrial locations. THHN is rated for dry and damp conditions, while THWN is also rated for wet locations. You will see these used in conduit runs, garages, basements, and commercial installations.
Metal-Clad and Armored Cable (MC and AC)
Metal-clad (MC) and armored cable (AC, sometimes called BX) wrap the conductors in a flexible metal sheath for added physical protection. They are common in commercial buildings and in residential applications where wiring is exposed or requires extra durability, such as basements and utility areas. The metal armor helps shield the conductors from damage.
Service Entrance Cable (SE and USE)
Service entrance cable carries power from the utility connection or meter into the home’s main panel and to large appliances. SE cable is used above ground, while USE is rated for underground service. Because these conductors carry the full electrical service, they are heavy-gauge and handled only by qualified electricians and utility professionals.
Low-Voltage and Specialty Cables
Not every cable in a home carries household current. Several low-voltage and signal cables are common:
- Coaxial cable (coax): Carries television, cable, and some internet signals, recognizable by its single center conductor and shielding.
- Ethernet (Cat5e, Cat6): Twisted-pair cabling for wired internet and data networks.
- Thermostat and doorbell wire: Thin low-voltage conductors for control systems.
- Speaker and security wire: Low-voltage cabling for audio and alarm systems.
These low-voltage cables are generally safer to handle, but anything tied into line-voltage power still belongs in a professional’s hands.
Understanding Wire Gauge
Cable size is described by American Wire Gauge (AWG), where a smaller number means a thicker wire that carries more current. Common residential gauges include 14-gauge for 15-amp lighting circuits, 12-gauge for 20-amp circuits, and heavier gauges for appliances and service. Using the wrong gauge for a circuit’s load is a serious fire hazard, which is one reason code compliance and professional installation matter.
Color Coding of Conductors
Inside a cable, the individual conductors are color-coded to indicate their function, which helps electricians wire safely and consistently. In typical North American residential wiring, black and red wires are hot conductors carrying current, white is the neutral, and green or bare copper is the ground. These conventions matter because miswiring a hot and neutral, or failing to properly ground a circuit, creates a shock and fire hazard. Understanding the color code helps you follow what an electrician is doing, but it is not a license to start connecting wires yourself.
Choosing the Right Cable for the Job
Selecting a cable is about matching it to the environment and the load. A few general principles guide the choice:
- Indoor, dry, protected runs typically use NM (Romex) cable.
- Underground or wet outdoor runs require UF cable or conductors in conduit rated for the conditions.
- Exposed or industrial areas call for conduit with THHN/THWN conductors or armored cable for physical protection.
- The circuit load and length dictate the wire gauge, since undersized wire overheats and longer runs may need a heavier gauge to limit voltage drop.
A licensed electrician weighs all of these factors against code requirements, which is exactly why the selection is not a guessing game.
Why You Must Hire a Licensed Electrician
Selecting and installing electrical cable is not a casual DIY task. Electrical work must comply with the NEC and local codes, typically requires permits and inspection, and carries real risks of fire, shock, and electrocution if done improperly. Always hire a licensed, insured electrician for wiring work, never work on energized circuits, and let a professional confirm the correct cable type, gauge, and protection for each application.
Final Thoughts
The common types of electrical cables, from NM Romex and UF underground feeder to THHN conductors in conduit, armored MC cable, and low-voltage coax and Ethernet, each serve a specific purpose in a home’s electrical system. Understanding them helps you follow a contractor’s plan and budget intelligently. Just remember that knowing the names is no substitute for professional installation. Leave the wiring to a licensed electrician working to code.
