Home Wiring Terms & Electrical Basics Guide

Who is this “home electrical guide” for?

This is for the general public to help understand electrical terms and the basics of how the United States power grid and your home works. After you are done reading this, you should be able to better communicate your electrical needs to a trained electrician.

NOTE: This is NOT a technical wiring guide for DIY electricians as electricity is dangerous and all electrical jobs should be handled by trained and certified professionals.gallon.”

This article will cover the following:

U.S. Power Grid

The United States electricity grid is a complex system in which electricity is generated at centralized power plants and decentralized units and is transported through a system of substations, transformers, transmission lines, and distribution lines that deliver the product to its end user, the consumer. Since large amounts of electricity cannot be stored (other than a large-scale rechargeable battery stationary energy storage product like Tesla’s Megapack), it must be produced as it is used.

Read more on the EPA’s website: https://www.epa.gov/green-power-markets/us-electricity-grid-markets

Electricity meter

An electric or energy meter measures the total power consumed over a time interval, typically expressed in kilowatt hours. Electric utilities use electric meters installed at customers’ premises for billing and monitoring purposes. The meters are usually calibrated in billing units, and read once each billing period. These meters are owned by the electrical company who supplies the energy and usually located outside of the building.


In electricity, the phase refers to the distribution of a load. A phase is the current or the voltage between an existing wire. Its waveform of electronic signals can be analyzed and visualized by an oscilloscope. An oscilloscope is a digital device that draws a graph showing the instantaneous signal voltage as a function of time.

Single Phase

The most common system is the single-phase system, which is mainly used in homes. A home’s single-phase system is derived from the US grid’s three-phase system with the use of a transformer to supply the proper voltage.

Three Phase

A three-phase system is standard in industrial or commercial buildings to provide the power needed for heavy loads. This system uses three wires, instead of the standard two, to provide more power and is considered to be “more efficient”.

Breaker panel, breaker box, or “fuse box”

The main circuit breaker panel is a junction box that safely distributes the power supply to your house. The circuit breaker box also houses smaller sub-switches that connect with specific areas of your house. These switches are called breakers, and their function is to prevent electrical fires by automatically shutting off the power when something goes wrong.

Circuit Breaker

A circuit breaker is designed to protect electrical circuits from damage. It does it by interrupting the current flow, it prevents the risk of fire, and protecting equipment.


A single pole breaker is ideal for household use with 120-volt circuits and 15-40 amps. The construction consists of one hot wire and one neutral wire.


The two poles on a double breaker are primarily used for a 240-volt circuit, 20-200 amps. This is used for dryers, EV chargers, and HVAC units.


Busbars are metal bars that conduct large amounts of current located in the back of a breaker panel. They are often made from materials such as copper or aluminum, and every home electrical panel has at least one busbar to distribute ac power evenly throughout the rows of circuit breakers. A circuit breaker plugs into this to receive power.


The volt is the unit of measurement for electrical potential, potential difference, and electromotive force in SI. It is equal to the voltage required to produce one watt of power when the current carrying capacity is one ampere.


The majority of light fixtures and indoor appliances in the United States use 120 volts, which is typically referred to as “line voltage” by those in the electrical industry.


240 volts is usually used for dryers, EV chargers, and heavy equipment. This is a more robust 3-prong or 4-prong plug. 


An ampere (or amp) is the unit of measure for electrical current. Current is represented by the letter “I” in equations, and it simply measures how quickly electrons flow through a conductor.

Wire gauge

The width of the wire is known as a gauge, and this affects the current it can carry safely.


A 12/2 wire is designed for a 20 amperage-rated circuit breaker and is typically utilized in lighting and outlet circuits as well as for refrigerators.


A 12/3 wire is used in buildings for circuits that use higher amperage than the standard 20 amps.


The 10/2 wire can handle heavy loads and is generally rated for loads as high as 70 amps.


A 10/3 wire is used for wiring 220-volt four-pronged outlets that power large appliances.


A 8/3 wire is used only indoors for wiring to appliances such as stoves and dryers throughout homes and buildings. It has a 40 amp rating.


A 6/3 wire rating is typically 55 amps.

Multimeter & voltage testers

These are tools to detect voltage. A voltage tester simply tells you if there is voltage present on a wire, whereas a multimeter can measure the level of voltage on the wire.

NM (Non-Metallic) Sheathed Cable (Romex®)

A non-metallic sheathed cable is an assembly of 2 or more insulated (typically three) conductors, with a protective outer layer or sheath made of material that is resistant to moisture and flame. 

Black “hot” wire

The black wire is the “hot” or active wire as it carries electricity from the breaker panel into the switch or light.

White “neutral” wire

The white wire is the “neutral” or unused electricity and current that gets sent back to the breaker panel.

Bare copper “ground” wire

Most ground wire is uncoated, or “bare.” It’s also often called grounding wire because it’s the most popular type of copper wire. Even though it doesn’t have a coating, bare copper still conducts electricity better than other types of copper wire.

Wire nuts

A cone-shaped (commonly plastic) device with a conductive interior and an insulating exterior that is applied over two (or more) wires to make an electrical connection.

Electrical switches

An electrical switch either completes or breaks the path of an electric current, stopping or starting the flow of electricity.

Two way switch

A two-way switch has two positions. In one position, the light is on. In the other, the light is off. This is the kind of switch you have in many rooms. There is one place to turn the light on or off. When you turn it on, you are completing a circuit, so the electricity is flowing to the light. When you turn it off, you have interrupted the flow.

Three-way switch

Three-way switches are used to control lights from two different points in a room. They are connected to a hot wire from the electric panel and a wire that connects to the light. However, they have two special wires that connect to each other, called travelers. These two wires create their own internal circuit so that if a light is off, either switch can turn it on. If the light is on, either switch can turn it off.


A device that either increases or decreases the brightness of an electric light.

Electrical outlets & receptacles

An outlet is a box where you can plug in your electronics. Receptacles are openings in the box that outlets fit into. The average outlet will have two three-prong receptacles. Fun fact, US’s three-prong wasn’t the standard until 1971.