Electrical Wire Types and Uses: Complete Guide for Homeowners

Walk down the wire aisle at any Home Depot and you face a wall of colored jackets, gauge numbers, and three-letter codes that mean nothing without a translation key. Knowing the basic electrical wire types and uses turns that wall from intimidating to navigable in about ten minutes — and it can save hundreds of dollars on a remodel where electricians charge by the hour to interpret the same code. This guide breaks down the wires that actually appear in residential work, where each one belongs by code, and how to pick gauge and amperage without guessing.

Reading the Wire Label

Every spool of building wire is printed with a sequence of letters and numbers that tells you exactly what is inside. A typical residential wire might read “14/2 NM-B 600V WG.” Breaking that down: 14 is the gauge (American Wire Gauge or AWG), 2 means two current-carrying conductors plus a ground (WG, with ground), NM-B is the cable type (Non-Metallic, type B), and 600V is the maximum voltage rating.

The smaller the AWG number, the thicker the wire and the more current it carries. A 12-gauge wire is thicker than 14-gauge. A 6-gauge is thicker still and used for high-draw appliances like ranges and water heaters.

NM-B (Romex): The Workhorse of Residential

Non-metallic sheathed cable, sold under the Romex brand by Southwire, makes up roughly 80 percent of the wire in a typical American home. It comes with two or three insulated conductors plus a bare copper ground inside a flexible plastic jacket. The jacket color tells you the gauge instantly — white for 14 AWG (15-amp circuits), yellow for 12 AWG (20-amp), orange for 10 AWG (30-amp), and black for 8 AWG (40 to 50-amp).

NM-B installs only in dry, protected locations inside the home — through stud bays, drilled joists, and inside walls. It must be at least 1.25 inches back from the front of a stud or have a nail plate, per NEC 300.4. Never run NM-B in conduit underground or in a wet location. A 250-foot roll of 12/2 NM costs about $145; a 14/2 roll runs around $95.

THHN/THWN: Conduit and Wet Work

Individual conductors marked THHN (Thermoplastic High Heat Nylon-coated) or THWN (Thermoplastic Heat and Water-resistant Nylon-coated) are the building blocks of any wiring run inside conduit. They come in solid copper for sizes 14, 12, and 10 AWG and stranded for 8 AWG and larger. THWN is rated for wet locations and is the standard for underground PVC conduit and exterior runs.

Color coding signals function: black, red, and blue for hot phases; white or gray for neutral; green or bare for ground. A 500-foot roll of 12 AWG THHN runs about $90. Most subpanel feeds, garage circuits, and outdoor lighting use THWN in conduit.

UF-B: Direct Burial Without Conduit

Underground Feeder cable looks like NM-B with a solid plastic jacket instead of the layered paper-and-plastic of Romex. UF-B can be buried directly in the ground without conduit at a minimum depth of 24 inches, or 12 inches if protected by GFCI and limited to 20 amps. It is the standard for detached garage feeds, post lights, and well pumps within 100 feet of the panel.

Pull UF-B through a sleeve where it exits the ground or passes under a driveway. UV exposure breaks down the jacket over years, so the part above grade should be protected by conduit or run inside a building.

MC and AC: Metal-Clad Cable

Metal-Clad (MC) cable wraps insulated conductors in a flexible aluminum or steel spiral armor. It is required in some commercial settings and in residential areas where rodent damage or fire concerns push above NM-B’s rating — basement ceilings in some jurisdictions, multi-family construction, and through fire-rated assemblies.

Armored Cable (AC, also called BX) is similar but uses the armor itself as part of the grounding path. Newer construction typically specs MC instead of AC because MC includes a dedicated green ground conductor inside the armor. A 250-foot coil of 12/2 MC runs about $235.

Service Entrance and Feeder Cable

SE (Service Entrance) and SER cable carry the heaviest power loads in a residential install. SER is used to feed a subpanel from the main panel — the three insulated conductors plus a bare ground handle 100 to 200 amps depending on gauge. A typical 100-amp subpanel feed uses 2-2-2-4 SER aluminum or 3-3-3-5 SER copper.

The main service drop from the meter to the main panel uses SE-U or SE-R cable, sized by the service rating: 4/0 aluminum for 200 amps, 2/0 aluminum for 150 amps, 1/0 aluminum for 100 amps. Most utilities require their own technicians to make this connection.

Common Gauges and Their Amperage

• 14 AWG copper: 15 amps — bedroom and general lighting circuits
• 12 AWG copper: 20 amps — kitchen counter receptacles, bathroom circuits, garage outlets
• 10 AWG copper: 30 amps — electric dryers, large window AC units
• 8 AWG copper: 40-50 amps — electric water heaters, smaller ranges
• 6 AWG copper: 55-65 amps — electric ranges, EV chargers, hot tubs
• 4 AWG copper: 70-85 amps — small subpanel feeds
• 2 AWG copper: 95-115 amps — 100-amp subpanel feeds

Low-Voltage Wire Around the House

Not every wire in a modern home runs at 120 or 240 volts. Thermostat wire (18/5 or 18/8) connects HVAC components. Cat6 Ethernet handles data drops. RG6 coaxial runs satellite and cable TV. 14/2 or 12/2 landscape wire feeds low-voltage path lights at 12 to 15 volts.

Doorbell and chime wire is typically 18/2 solid copper. Audio speaker wire ranges from 16 to 12 gauge depending on run length and impedance. None of these require permits or licensed electricians in most jurisdictions, which makes low-voltage work a good DIY entry point.

Where Each Wire Lives in the House

Walk through a typical 2,200 square-foot home and you will find NM-B in every wall and ceiling, THWN running through PVC conduit from the panel to the EV charger in the garage, UF-B buried out to the shed, SER feeding the subpanel in the basement, low-voltage Cat6 and coax in a structured wiring panel near the entry, and 18/5 thermostat wire running between the furnace and the wall stat. The mix is normal — there is no single wire type that does everything.

Code Basics That Drive Wire Selection

The National Electrical Code (NEC) updates every three years, but a few rules drive most residential wire decisions. AFCI breakers are required on most living-space circuits since 2014. GFCI protection is required on kitchen, bath, garage, basement, outdoor, and laundry receptacles. Tamper-resistant receptacles are required throughout dwellings. EV charger circuits typically need their own 40 or 50-amp 240-volt feed.

Pull a permit before any meaningful electrical work. An inspector signs off on wire type, gauge, breaker sizing, and box fill — the four things that most commonly fail when a homeowner does electrical without guidance. The $75 to $200 permit fee is cheap insurance against a panel fire or a denied homeowners claim later.