Electrical Terms Glossary

Understanding common electrical terminology to help you communicate with your electrician

A

AC (Alternating Current)
The type of electrical current used in homes and businesses. The flow of electricity periodically reverses direction, which is different from DC (direct current). Standard household power in the US is 120V AC at 60Hz.
AFCI (Arc-Fault Circuit Interrupter)
A safety device that detects dangerous electrical arcs and shuts off power to prevent fires. Required by code in bedrooms, living rooms, and most living spaces. Often combined with GFCI protection in newer homes.
Amp (Ampere)
The unit of measurement for electrical current flow. Think of it like water flow through a pipe. Common household circuits are 15 or 20 amps. Your electrical panel's capacity is measured in amps (100A, 200A, etc.).
Ampacity
The maximum amount of electrical current a wire or device can safely carry without overheating. Wire gauge determines ampacity—thicker wires can carry more current.

B

Ballast
A device that regulates current to fluorescent and HID lights. Older magnetic ballasts have been largely replaced by more efficient electronic ballasts. If your fluorescent lights flicker or hum, the ballast may need replacement.
Bonding
Connecting metal parts of the electrical system together to ensure they're all at the same electrical potential. Proper bonding prevents shock hazards and helps circuit breakers trip when needed.
Box (Electrical Box / Junction Box)
An enclosure where electrical connections are made. All wire connections must be made inside a box—exposed wire splices are a code violation and fire hazard.
Branch Circuit
An individual circuit that runs from your electrical panel to outlets, lights, or appliances. Most homes have multiple branch circuits, each protected by its own breaker.
Breaker (Circuit Breaker)
A safety device that automatically shuts off power when a circuit is overloaded or short-circuited. Found in your electrical panel. Unlike fuses, breakers can be reset after they trip.
Bus Bar
A metal strip inside your electrical panel that distributes power to the circuit breakers. Your panel has hot bus bars (carrying power) and neutral/ground bus bars.

C

Circuit
A complete path for electricity to flow from the source, through a device, and back. When you flip a switch, you're completing or breaking a circuit.
Conductor
A material that allows electricity to flow through it easily. Copper and aluminum are common electrical conductors. The wires in your walls are conductors.
Conduit
A protective tube that houses electrical wires. Can be metal (EMT, rigid) or plastic (PVC). Required in exposed locations and commercial buildings.
Current
The flow of electricity through a conductor, measured in amps. Like water flowing through a pipe, current is the actual movement of electrons.

D

DC (Direct Current)
Electrical current that flows in one direction only. Batteries produce DC power. Solar panels generate DC, which must be converted to AC for home use.
Dedicated Circuit
A circuit that serves only one appliance or outlet. Required by code for major appliances like refrigerators, dishwashers, microwaves, and HVAC equipment.
Demand Load
The actual amount of electrical power being used at any given time. Electricians calculate demand load to properly size panels and circuits.
Dimmer Switch
A switch that controls light brightness by varying voltage. Modern dimmers work with LED bulbs but must be rated for LED use. Older dimmers may cause flickering with LEDs.
Double-Pole Breaker
A circuit breaker that controls both hot wires in a 240V circuit. Used for large appliances like dryers, ranges, water heaters, and EV chargers.

E

Electrical Panel (Breaker Box / Load Center)
The main distribution point for electricity in your home. Contains circuit breakers and connects to your utility meter. Common sizes are 100, 150, and 200 amps.
EMT (Electrical Metallic Tubing)
Thin-walled metal conduit commonly used in commercial and exposed residential installations. Provides physical protection for wires.
EV Charger (Electric Vehicle Charger)
Equipment that charges electric vehicles. Level 1 uses standard 120V outlets. Level 2 requires a 240V dedicated circuit (typically 40-50 amps) for faster charging.

F

Fault
An abnormal condition in an electrical system, such as a short circuit or ground fault. Faults can cause breakers to trip or create safety hazards.
Feeder
The wires that carry power from the main panel to a sub-panel or from the meter to the main panel.
Fish Tape
A tool electricians use to pull wires through walls, ceilings, and conduit. Essential for adding circuits to existing construction.
Fuse
An older overcurrent protection device that melts when overloaded, breaking the circuit. Must be replaced after tripping. Largely replaced by resettable circuit breakers in modern homes.

G

Gauge (Wire Gauge)
A measurement of wire thickness. Lower numbers = thicker wire. Common residential sizes: 14 gauge (15A circuits), 12 gauge (20A circuits), 10 gauge (30A circuits). AWG = American Wire Gauge.
Generator
A device that produces electricity, typically from fuel combustion. Standby generators automatically power your home during outages. Proper installation requires a transfer switch.
GFCI (Ground Fault Circuit Interrupter)
A safety device that instantly shuts off power when it detects current flowing through an unintended path (like through a person). Required in bathrooms, kitchens, garages, outdoors, and near water sources.
Ground (Grounding)
A safety connection to the earth that provides a path for fault current. The bare copper or green wire in your electrical system. Essential for safety and proper operation of GFCI/AFCI devices.
Ground Rod
A metal rod driven into the earth to provide a grounding connection for your electrical system. Typically 8 feet long copper or copper-clad steel.

H

Hertz (Hz)
The unit measuring electrical frequency—how many times per second AC current alternates. US power is 60Hz. Some appliances from overseas require 50Hz power.
Home Run
A dedicated wire that runs directly from a device to the electrical panel without connecting to other outlets or devices along the way.
Hot Wire
The wire that carries current from the panel to your devices. Usually black or red. This is the "live" wire that can shock you if touched.

I

Insulation
The protective covering around electrical wires that prevents current leakage and contact. Wire insulation is rated for specific temperatures and conditions (THHN, NM, etc.).
Inverter
A device that converts DC power to AC power. Used in solar systems, battery backup systems, and some generators. Quality inverters produce "pure sine wave" power that's safe for sensitive electronics.

J

Junction Box
An enclosed box where wires are connected or spliced. All electrical connections must be made inside junction boxes with accessible covers.
Joule
A unit of energy. Surge protector ratings use joules to indicate how much energy they can absorb. Higher joule ratings = better protection.

K

Kilowatt (kW)
1,000 watts. Used to describe the power consumption of large appliances and the output of generators. A typical home might use 10-15 kW during peak demand.
Kilowatt-Hour (kWh)
The unit your utility uses to bill you. One kWh = using 1,000 watts for one hour. Your electric meter tracks kWh consumption.
Knockout
Pre-scored holes in electrical boxes that can be "knocked out" to allow wire entry. Unused knockouts must remain closed.

L

LED (Light Emitting Diode)
Energy-efficient lighting technology that uses 75-80% less energy than incandescent bulbs. LEDs last 15-25 times longer but require compatible dimmers.
Load
Any device that uses electricity—lights, appliances, motors, etc. "Load calculation" determines how much electrical capacity your home needs.
Load Center
Another name for your electrical panel or breaker box. The central point where power is distributed to branch circuits.
Low Voltage
Electrical systems under 50 volts, including doorbells, thermostats, landscape lighting, and security systems. Generally safer but still requires proper installation.
Lumen
The unit measuring light output. A 60W incandescent bulb produces about 800 lumens. When shopping for LEDs, compare lumens rather than watts.

M

Main Breaker
The large breaker at the top of your panel that controls power to all other breakers. Turning this off disconnects power to your entire home (but not the meter).
Meter
The device that measures your electricity consumption. Your utility company reads it to calculate your bill. Smart meters transmit readings automatically.
Multi-Wire Branch Circuit (MWBC)
A circuit that shares a neutral wire between two hot wires on opposite phases. Common in older homes. Requires special handling and a double-pole breaker or handle tie.

N

NEC (National Electrical Code)
The standard for safe electrical installation in the US. Updated every three years. Local jurisdictions may adopt the NEC with modifications. Your electrician follows NEC requirements.
Neutral Wire
The white wire that completes the circuit by returning current to the panel. The neutral carries current during normal operation and should never be confused with the ground wire.
NM Cable (Romex)
Non-metallic sheathed cable commonly used in residential wiring. Contains hot, neutral, and ground wires inside a plastic jacket. "Romex" is a brand name that's become generic.

O

Ohm
The unit of electrical resistance. Higher resistance = less current flow. Ohm's Law (V=IR) relates voltage, current, and resistance.
Outlet
A point in the electrical system where current is taken to supply equipment. Includes receptacles (plug outlets), lighting outlets, and hardwired connections.
Overcurrent
Current that exceeds the rated capacity of a wire or device. Circuit breakers and fuses protect against overcurrent conditions that could cause fires.
Overload
When a circuit carries more current than it's designed for. Signs include warm outlets, flickering lights, and frequently tripping breakers.

P

Panel Upgrade
Replacing your electrical panel with a larger capacity unit. Common upgrades: 100A to 200A. Often needed for EV chargers, heat pumps, or when adding significant electrical loads.
Permit
Authorization from your local building department to perform electrical work. Required for most electrical projects. Ensures work is inspected for safety and code compliance.
Phase
The timing relationship of AC power waves. Residential service is typically single-phase (two hot legs 180° apart). Commercial buildings often use three-phase power.
Pigtail
A short piece of wire used to connect multiple wires to a single device terminal. Proper pigtailing technique ensures reliable connections.
Polarized Plug
A plug with one blade wider than the other, ensuring it connects hot to hot and neutral to neutral. Important for safety in many appliances.

R

Raceway
An enclosed channel for wires, including conduit, wireways, and cable trays. Protects wires and allows for future changes.
Receptacle
The technical term for an electrical outlet where you plug things in. Standard household receptacles are 15A or 20A, 120V.
Resistance
Opposition to current flow, measured in ohms. All conductors have some resistance. High resistance causes heat, which is why loose connections are dangerous.
Romex
Brand name for NM (non-metallic) cable, commonly used as a generic term. The plastic-sheathed cable found in most residential walls.

S

Service Entrance
The point where utility power enters your home, including the meter, service cable, and main disconnect. The utility owns everything up to the meter; you own everything after.
Short Circuit
When current flows through an unintended path, bypassing the load. Creates very high current that trips breakers instantly. Often caused by damaged wire insulation.
Single-Pole Breaker
A breaker that protects one hot wire on a 120V circuit. The most common type in residential panels.
Smart Switch
A switch that can be controlled remotely via app, voice assistant, or automation. Most require a neutral wire, which older homes may lack.
Subpanel
A secondary electrical panel fed from the main panel. Used to add circuits in garages, workshops, additions, or when the main panel is full.
Surge Protector
A device that protects equipment from voltage spikes. Whole-house surge protectors install at your panel. Point-of-use protectors plug into outlets.

T

Tamper-Resistant Receptacle (TR)
An outlet with built-in shutters that prevent children from inserting objects. Required by code in all new residential construction. Marked "TR" on the face.
Three-Way Switch
A switch that works with another three-way switch to control a light from two locations. Common at stairs and long hallways. Has three terminals plus ground.
Transfer Switch
A device that safely switches your home's power source between utility and generator. Prevents dangerous backfeed to utility lines. Required for permanently installed generators.
Transformer
A device that changes voltage levels. Step-down transformers reduce voltage (utility pole to home). Low-voltage lighting uses small transformers.
Tripped Breaker
A breaker that has automatically shut off due to overload, short circuit, or ground fault. The handle moves to a middle position. Reset by turning fully off, then on.

U

UL Listed
A product tested and certified by Underwriters Laboratories as safe for its intended use. Always look for UL listing on electrical products.
Ungrounded Outlet
An older two-prong outlet without a ground connection. Cannot safely power three-prong devices. Upgrading often requires running new wiring.
USB Outlet
A receptacle with built-in USB ports for charging devices without adapters. Modern versions include USB-C with Power Delivery for faster charging.

V

Volt (Voltage)
The unit measuring electrical pressure or force. Standard US household circuits are 120V. Large appliances (dryers, ranges, EV chargers) use 240V.
Voltage Drop
The loss of voltage over distance in a wire. Causes dim lights and underperforming equipment at the end of long runs. Solved by using larger wire gauge.

W

Watt
The unit of electrical power. Watts = Volts × Amps. A 100W light bulb uses more power than a 60W bulb. Your electric bill is based on watt-hours consumed.
Weatherproof
Equipment rated for outdoor use. Outdoor outlets require weatherproof covers that seal when plugs are inserted. Different ratings exist for wet and damp locations.
Whole-House Surge Protection
A surge protection device installed at your electrical panel that protects all circuits from voltage spikes. Provides first-line defense against lightning and utility surges.
Wire Nut
A twist-on connector used to join two or more wires together. Properly sized wire nuts are essential for safe, code-compliant connections.

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