Wire and Cable Basics
First, understand the difference between wire and cable:
- A wire is a single conductor that carries an electrical current through a circuit.
- A cable is a collection of wires encased in a protective jacket.
Most conductors are copper, which is corrosion resistant and a better conductor than aluminum. Aluminum serves as a less expensive, lightweight alternative.
The American Wire Gauge (AWG) system provides standard wire gauge sizes. The higher the gauge number, the smaller the diameter of the wire. See the Wire Gauge chart below for examples. The National Electrical Code (NEC) mandates the regulations for wire and cable for electrical applications.
Wiring and cable installation should be left to a licensed electrician and requires a permit and inspection. Applicable codes must be observed and the manufacturer’s instructions for use and safety must be followed. Contact a licensed electrician for questions about connections or wiring.
Key Electrical Definitions
- Amperage: The amount of electric current moving through a circuit
- Wire Gauge Amp Rating: The electrical load capacity of a particular wire size
- Voltage: The difference in electrical potential between two points
- Voltage Drop: The difference between measurements at each terminal of a device
- Wattage: The amount of electrical power that’s used or produced
Wire Amperage Chart
The wire amp chart above will help you understand the correct amperage ratings for different types of wire. This ampacity chart is a general reference only. Always defer to electrical codes and manufacturer’s specifications.
Electrical Wire Gauge Chart
The AWG wire size chart above will help you determine recommended circuit lengths for voltage drop. This is a general reference only. Defer to electrical codes and manufacturer’s specifications.
Types of Electrical Wire
TFFN, THHN and THWN are designations for three common types of wire.
TFFN Wire
Thermoplastic flexible fixture nylon (TFFN) wire:
- Works for fixtures, appliances, control circuits
- Suitable for machine tool wiring if rated MTW
- Stranded conductor
- Rated for 600 volts
- Has PVC insulation and a nylon jacket
- Highly flexible and easy to route and connect
- Oil resistant
- Maximum conductor temperature of 90 degrees Celsius in dry environments
- If also rated as MTW, is suitable for wet conditions and temperatures up to 60 degrees Celsius
- Sunlight-resistance rating required for outdoor use
THHN Wire
Thermoplastic high-heat-resistant nylon (THHN) wire:
- Works for outlets, lighting, appliances, control circuits, machine tools
- Can be stranded or solid
- Rated for up to 600 volts
- Has PVC insulation and a nylon jacket
- Abrasion, oil and chemical resistant
- Maximum conductor temperature of 90 degrees Celsius in dry environments
- Typically marked as THHN/THWN (suitable for wet environments and conductor temperatures up to 75 degrees Celsius) or THHN/THWN-2 (rated for conductor temperatures in wet environments up to 90 degrees Celsius)
- Intended for use in raceways or conduit
- Not suitable for direct burial — must be in a conduit to prevent damage
THWN Wire
Thermoplastic heat- and water-resistant nylon (THWN):
- Works for applications such as outdoor lighting, outdoor power outlets, pool pumps
- Suitable for use in crawlspaces and basements
- Can be stranded or solid
- Rated for 600 volts
- Has PVC insulation and a nylon jacket
- Water and oil resistant
- Suitable for wet environments
- Maximum conductor temperature of 90 degrees Celsius in dry conditions and 75 degrees Celsius in wet conditions; when also designated THWN-2, rated for 90 degrees Celsius in wet and dry conditions
- Not suitable for direct burial – must be in a conduit to prevent damage
THHN vs. THWN Wire
THHN and THWN wire are both suitable for residential, commercial and industrial settings, are both rated for 600 volts and are rated for conductor temperatures up to 90 degrees Celsius in dry locations. However, THHN is only suitable for dry locations unless it also has a THWN designation. THWN wire is water-resistant and suitable for wet locations with conductor temperatures up to 75 degrees Celsius. THWN-2 cable is rated for conductor temperatures in wet environments up to 90 degrees Celsius.
Types of Cable
A home contains many types of cable, from the cable that connects your home to an electrical utility, to the cable that connects speakers to a sound system.
Category Cable: This cable, also known as ethernet cable, is in phone and data networking systems. Cat 5e and Cat 6 are the most common variety for networking in homes and small businesses. The conductor pairs are twisted together to prevent crosstalk and interference from other paired conductors in the cable, as well as external interference. The higher the megahertz (MHz) capability, the more twists per foot.
Coaxial Cable: This is a metallic cable that carries television and video signals. It connects to video equipment and features a central conductor with a dielectric insulator, metallic shield and plastic jacket. Coaxial cable with Bayonet Neill-Concelman quick-attach/release connectors is known as BNC cable.
Doorbell Wire: Doorbell wire connects a wired doorbell or video doorbell to a home electrical system. 18-gauge wire is the most common variety.
Lamp Cord: A type of flexible cord for lamps, small appliances, radios and other similar products that don’t exceed 150 or 300 volts, depending on the type. Lamp cord is available between 18- and 12-gauge sizes in a variety of colors.
Landscape Lighting Low-Voltage (LV) Cable: This cable works for outdoor accent lighting, landscape lighting and security lighting but is not suitable for 120-volt circuits. Applications shouldn’t exceed 150 volts. It’s suitable for sunlight and is available between 16- and 8-gauge sizes. Some LV cable is suitable for direct burial.
NM-B: This is a non-metallic sheathed cable in residential building wiring. It’s used only in dry, interior, protected locations in branch circuits for outlets, lighting and other residential applications. NM-B is available between 14 AWG and 6 AWG with two or three conductors and a bare ground.
Pole Transformer (Multiplex Service Drop): Overhead cabling that transmits power from the electrical utility to the service entrance of a home. The cable contains multiple wires twisted around each other for flexibility and strength. Insulation protects the conductors from weather, ultraviolet (UV) rays, etc. This cable also includes a neutral wire that might be insulated or bare.
Preassembled Whips: These are pre-cut lengths of armored cable designed to increase jobsite productivity. The assemblies come with pre-stripped THHN conductors and pre-installed zinc diecast snap-in fittings.
Residential Grounding Wire: This bare copper wire is available in 4-, 6-, and 8-gauge solid or stranded construction. It’s commonly used to connect a home’s electrical system to grounding electrodes. 8-gauge solid copper wire can also be used to bond metal components around swimming pools.
Security System/Fire Alarm: This is a specialized type of low-voltage cable that carries power and information to hardwired cameras, motion detectors, smoke and fire alarms, etc. Shielded cable has protection against interference. Cable used in fire alarm systems must be rated for that application and have a flame-resistant jacket.
Service Entrance Cable: This cable includes individual conductors rated XHHW/XHHW-2 or THHN/THWN, in a flame-retardant jacket. Depending on the type, SE cable feeds power from the electric utility to the main service disconnect of a home or commercial building, or from the main panel to a subpanel. It can be exposed to direct sunlight and used in wet or dry locations.
- SER (Service Entrance, Round): SER cable includes two or three hot insulated conductors, an insulated neutral and a bare ground running parallel in a round jacket. SER is used aboveground to feed service from the panel to other panels in residential and commercial buildings
- SEU (Service Entrance, Unarmored): Bare neutral conductor strands are helically wound around the two parallel insulated conductors, with no ground. It’s used for single-family residential buildings to convey power from the service drop to the meter base and from the meter base to the main service disconnect.
Speaker Wire: Speaker wire includes two copper conductors in a protective jacket. It’s used in sound systems to transport a low-voltage electrical current to speakers.
Sprinkler Wire: Multi-conductor sprinkler wire is suitable for direct burial on applications up to 30 volts. It’s used in central controls for underground sprinkler systems and is available in 18-gauge construction with up to 25 conductors.
Thermostat Wire: Used in heating and air conditioning systems, along with bell and alarm systems, thermostat wire is available in 20- or 18-gauge sizes with up to 10 conductors.
Underground (UF-B) Wire: This is a copper wire suitable for direct burial on 120-volt residential branch circuits. It comes in a gray jacket and can be used for deck lighting, outdoor water features, and landscape lighting.
Underground Residential Distribution (URD) Cable: Used for secondary distribution and underground service applications at 600 volts or less, such as from a pad transformer to a home service entrance. It’s suitable for direct burial or placement in ducts but is not for use inside a home, connection to a service panel or as building wire. It’s acceptable in wet locations in triplex or quadruplex. Conductors are stranded, compressed aluminum. The neutral conductor has a yellow, triple-extruded stripe.
Other Cable Types
In addition to the common types of wire and cable above, you’ll also find these cables in some applications.
Armor-Clad (AC) Cable: AC cable includes thermoplastic-insulated conductors rated for 600 volts and an aluminum bonding wire inside interlocking aluminum armor. The bonding wire maintains electrical continuity throughout the cable, allowing the armor to serve as the equipment grounding path.
Automotive Cable or Primary Wire: This is a general-purpose thermoplastic (GPT) wire. Normal applications are within motor vehicles with limited exposure to fluids, physical wear and abuse.
Flexible Cord: Typically used for industrial machinery, washing machines and large appliances, portable tools, equipment and extension or power cords, flexible/power cord has its own naming convention based on a letter code, with a common option being SJEOOW:
- S: service cord (when not followed by a J, V or P; also indicates a rating of 600 volts)
- J: junior service cord, 300 volts
- T: thermoplastic
- E: elastomer, thermoplastic that looks and feels like rubber
- O: oil-resistant outer jacket
- OO: oil-resistant outer jacket and oil-resistant insulation
- P: parallel cord (light duty, flat)
- V: vacuum cleaner cord (light duty, round)
- W: sunlight- and moisture-resistant
Metal-Clad (MC) Cable: MC cable is common for commercial electrical work, applications that require running cable through concrete or in other commercial environments. Individual THHN wire conductors and grounding wire run through an aluminum interlocked armor.
Mobile Home Feeder: This cable connects a mobile home to a supply of electricity where permanent wiring is required. It’s suitable for direct burial and use as underground service entrance cable. It typically includes four insulated aluminum conductors — two hot conductors, a white-striped neutral and a green grounding conductor — rated for 600 volts.
Submersible Pump Cable: This includes copper conductors that are heat-, moisture-, oil- and gasoline-resistant. It’s rated for maximum conductor temperatures of 60 or 75 degrees Celsius, depending on type, with two or three conductors. It’s used for power and circuits for submersible pump systems.
How to Identify Wires and Cables
Information printed on wire and cable jackets helps identify the capabilities of the wire to allow pros to select the correct product for a job. Information includes the wire material, gauge and voltage rating, and an NEC letter code that identifies the attributes of the wire.
Common Residential Electric Wiring Attributes
You’ll often see combinations of these letters and attributes in residential wiring:
- T: thermoplastic insulation
- FF: flexible fixture
- H: heat resistance
- HH: high heat resistance
- W: suitable for wet locations
- N: nylon coating, resistant to damage by oil or gas
- X: synthetic polymer, flame-resistant
Wire Colors
Industry-standard wire jacket coloring identifies a wire's purpose:
- Black: Hot wire for switches or outlets
- Red: Hot wire for switch legs and connections to hardwired smoke detectors
- Blue and Yellow: Often installed as hot wires pulled through conduit; blue is often used for three- or four-way switch applications, and yellow commonly serves as switch legs to control fans, lights, etc.
- White: Neutral (can be hot if marked with black or red to indicate it's no longer a neutral)
- Green and Bare Copper: Grounding purposes only
Installation may differ from industry standards. Always assume a wire is energized, regardless of its color, until you test it.
Common Applications for NM-B Cable
NM-B cable is common in residential wiring and, depending on codes, light-duty commercial wiring. NM-B creates circuits that send power to light switches, electrical outlets, appliances, water heaters and more.
Designations of NM-B cable indicate the gauge of the wire and the number of conductors. For example, 12/2 NM-B includes 12-gauge wire and two conductors. Different jacket colors also indicate the gauge of the wire inside. We list wire gauge amp ratings and wattage limits for different types of NM-B cables below, along with common uses. Note that NM-B cable must use a temperature rating of 60 degrees Celsius, regardless of the temperature ratings of the individual conductors.
Use the information below as a general guide only. Actual ampacity and wattage limits depend on factors such as ambient temperature, how many current-carrying wires are in the cable, insulation type, temperature ratings of the wires, and the connected devices and terminals. Any electrical installation requires confirmation of correct wire size, conductor ampacity, load and breaker rating, and must follow NEC requirements and the manufacturer’s specifications.
14-Gauge NM-B Cable
Cable With 14-Gauge Wire: Amp Rating, Wattage Limits and Jacket Color
- Allowable Amps: 15 amps
- Recommended Continuous Wattage (80% load) at 120 volts: 1440 watts
- Maximum Wattage at 120 volts: 1800 watts
- Typical Jacket Color: White (two conductors) or blue (three conductors)
Cable with 14-Gauge Wire: Applications
Depending on device specifications, applications include:
- Light Fixtures and Wall Switches: 14/2 NM-B cable with ground
- Grounded, General-Purpose 15A Receptacles: 14/2 NM-B cable with ground
- Level 1 Electric Vehicle Charger (12 amps or less): 14/2 NM-B with ground
- Ceiling Fan/Light/Switch: 14/3 NM-B cable with ground
- Three-Way Switches: 14/3 NM-B cable with ground
12-Gauge NM-B Cable
Cable With 12-Gauge Wire: Amp Rating, Wattage Limits and Jacket Color
- Allowable Amps: 20 amps
- Recommended Continuous Wattage (80% load) at 120 volts: 1,920 watts
- Maximum Wattage at 120 volts: 2,400 watts
- Recommended Continuous Wattage (80% load) at 240 volts: 3,840 watts
- Maximum Wattage at 240 volts: 4,800
- Typical Jacket Color: Yellow (12/2) or purple (12/3)
Cable With 12-Gauge Wire: Applications
Depending on device specifications, applications include:
- Dishwasher (20 amps or less): 12/2 NM-B cable with ground
- Refrigerator (20 amps or less): 12/2 NM-B cable with ground
- Freezer (20 amps or less): 12/2 NM-B cable with ground
- A/C Window Unit (20 amps or less): 12/2 NM-B w/ ground
- Bathroom Exhaust Fan/Light: 12/2 NM-B cable with ground
- Workshop Outlet (20 amps or less): 12/2 NM-B cable with ground
- Exhaust Fan/Light/Heater: 12/3 cable with ground
10-Gauge NM-B Cable
Cable With 10-Gauge Wire: Amp Rating, Wattage Limits and Jacket Color
- Allowable Amps: 30 amps
- Recommended Continuous Wattage (80% load) at 120 volts: 2,880 watts
- Maximum Wattage at 120 volts: 3,600 watts
- Recommended Continuous Wattage (80% load) at 240 volts: 5,760 watts
- Maximum Wattage at 240 volts: 7,200
- Typical Jacket Color: Orange (10/2) or pink (10/3)
Cable With 10-Gauge Wire: Applications
Depending on device specifications, applications include:
- Wall Heater (30 amps or less): 10/2 NM-B with ground
- Clothes Dryer (30 amps or less): 10/3 NM-B with ground
- Single Oven (30 amps or less): 10/3 NM-B with ground
The NEC limits maximum breaker sizes for the small copper conductors above, regardless of the insulation type or higher ampacities in tables:
- 14AWG: 15A
- 12AWG: 20A
- 10AWG: 30A
8-Gauge NM-B Cable
Cable With 8-Gauge Wire: Amp Rating, Wattage Limits and Jacket Color
- Allowable Amps: 40 amps
- Recommended Continuous Wattage (80% load) at 240 volts: 7,680 watts
- Maximum Wattage at 240 volts: 9,600 watts
- Typical Jacket Color: Black (8/2) or gray (8/3)
Cable With 8-Gauge Wire: Applications
Depending on device specifications, applications include:
- Wall Oven (40 amps or less): 8/3 NM-B with ground
- Cooktop (40 amps or less): 8/3 NM-B with ground
6-Gauge NM-B Cable
Cable With 6-Gauge Wire: Amp Rating, Wattage Limits and Jacket Color
- Allowable Amps: 55 amps
- Recommended Continuous Wattage (80% load) at 240 volts: 10,560 watts
- Maximum Wattage at 240 volts: 13,200 watts
- Typical Jacket Color: Black (6/2) or gray (6/3)
Cable With 6-Gauge Wire: Applications
Depending on device specifications, applications include:
- Double Oven (50 amps or less): 6/3 NM-B with ground
- Double Oven Range (50 amps or less): 6/3 NM-B with ground
NM-B cable jacket colors may vary by manufacturer and by the age of the cable.
Electrical Tools and Accessories
Boxes: These house wiring, outlets or switches for lights, ceiling fans, kitchen appliances, etc.
Circuit Breakers and Fuses: These devices prevent damage by interrupting the current during an overload or short. Homes built after the 1960s typically use circuit breakers rather than fuses.
Electrical Tape: This black adhesive tape can be used to identify wire, repair or splice electrical cable and insulate wire.
Outlets and Adapters: When wires are connected to an outlet or adapter, it allows the electrical current to power anything plugged into it, such as a kitchen appliance.
Non-Contact Electrical Tester: Testers let you check a circuit to see if it’s carrying electrical current.
Wire Connectors: These connect two or more wires together. See our DIY Basics video: How Do I Connect Two Wires?
Wire Cutter or Cable Cutter: This tool is used to cut directly through wire or cable. Different cutters are suitable for different types of wire and cable.
Wire Stripper: This device removes the plastic casing to expose the bare wire underneath. Most strippers offer multiple slots for a variety of wire sizes, while some have an adjustment dial to set the correct size.
Residential Wiring and Cable Key Points
- A wire is a single conductor, while a cable is a collection of multiple wires.
- Installing electrical wire and cable requires following local codes and manufacturer’s specifications.
- The National Electric Code designates wire and cable for specific applications.
- Wire type and gauge determines how much current a wire can safely handle.
- Wires and cables have naming and color conventions that help identify type and capabilities.
- Lower-gauge wire has a larger diameter, can carry more current and is suited for higher-wattage power use.
- The right electrical tools are necessary for safe, efficient electrical work.
Lowes.com has wire and cable for home and commercial electrical applications, as well as the tools, materials and accessories necessary for a safe, code-compliant installation. At a Lowe’s store, a Lowe’s Red Vest associate can help with wiring and cable needs, as well as any other items necessary to do the work right.
Wire and Cable FAQ
Find answers to common questions about wire and cable to understand how different types work for different applications.
What Are Capabilities of 12-Gauge vs. 14-Gauge Wire?
12- and 14-gauge electrical wire have different amperage and wattage limits. In NM-B cable, 12-gauge wire is rated for 20 amps with a recommended continuous wattage of 1,920 watts on a 120-volt circuit and 3,840 watts on a 240-volt circuit. 14-gauge electrical wire is smaller, so the maximum 14-gauge wire amperage in NM-B cable is rated lower at 15 amps. The wire is recommended for continuous wattages of 1440 watts or less on a 120-volt circuit. It’s typically not used on a 240-volt circuit in residential electrical wiring.
What Is 12 AWG Wire Used For?
12 AWG or 12-gauge wire in NM-B cable is suitable for use on 20-amp circuits. Depending on the amperage requirements of the appliances and fixtures, 12-gauge wire can conduct power to refrigerators, dishwashers, bathroom exhaust fans and workshop electrical outlets.
How Do Wire Gauge and Amps Relate to Each Other?
The NEC (National Electrical Code) sets maximum amp ratings for each electrical wire gauge. In general, the lower the wire gauge, the larger the diameter of the wire and the more amps (or electrical current) the wire can carry.