Sarah, who was replacing her kitchen outlet, called us last month very confused and somewhat embarrassed because of her purchase on a standard outlet replacement she thought she was making at the hardware store. When she got home and opened the package of her new replacement, she noticed it only had one set of plug slots (not two) like she’s used to. Sarah was not sure if she was having an issue with the outlet. So, she contacted GOG Electric to find out if she had made a mistake. Rather than having bought a standard two receptacle duplex outlet, Sarah bought a single receptacle outlet. It is easy to confuse a single receptacle with a duplex receptacle; therefore, people have trouble deciding what type of receptacle they need when needing one. This article will explain what a duplex receptacle is, how a duplex receptacle differs from other types of receptacles, and why knowing the differences matters for safety, code compliance, and general convenience throughout your everyday life.
The Face You See Every Day: Understanding the Duplex Design
The duplex outlet is commonly found in a home. A duplex outlet has two vertical, side-by-side receptacles that share a common connection for electrical current but otherwise operate independently of each other (they have separate hot and neutral terminals). After removing the wall cover and wall box, you will find one plastic body with two sets of terminals for each receptacle; or an interconnected set of terminals with a tab that allows for both receptacles to be connected to the same circuit with a single electrical box. The receptacle’s face has a small center screw opening to hold on the cover plate and two oval openings to accept plugs: each opening has a narrow hot lead, a wide neutral lead and a round ground lead. All other residential outlets are compared to the duplex outlet. If you want to learn more about how to incorporate a duplex outlet into a complete modern residential electrical system, see our recommendations for the best electrical outlets and switches for modern residential applications.
Counting Receptacles: The NEC Definition vs. Everyday Language
An area of confusion that many people are faced with is if a duplex outlet is one or two outlets. According to the National Electrical Code (NEC), a “receptacle” is defined as “a contact device installed at an outlet for connecting one plug.” In this way, a duplex is made up of two receptacles mounted on one yoke. Therefore, even though many electricians and homeowners will call this entire device an “outlet,” it is treated by the NEC as two separate points for purposes of meeting the required number of receptacle outlets for the wall space. In essence, the duplex meets the requirement of two outlets because it provides two plug-in points from one point of installation. On the other hand, a standard receptacle — the type that Sarah inadvertently purchased — will only provide one plug-in point, and these are used for dedicated circuits where only one item shall be connected, such as a refrigerator, washing machine, or sump pump. The difference physically can be seen with the number of plug slots — a standard receptacle has one set of slots, while a duplex has two.
Single vs. Duplex: Choosing the Correct Device for the Circuit
Duplex and single type receptacles can be used depending on their usage according to NEC rules, but can also be based on requirements associated with other factors.
- Duplex receptacles Living rooms, bedrooms, hallways, and kitchens commonly use general-purpose branch circuits that permit plugging multiple devices into a single wall outlet.
- Single receptacles Typically, these items have an individual branch circuit established for them. Usually, a large appliance has its own individual branch circuit which it cannot share with any other device. An acceptable configuration is one that recognizes that there can be only one refrigerator connected to a 20-amp receptacle.
When you’re changing out an electrical receptacle, if the one being replaced has two receptacles, use a duplex rather than a single. Installing a single receptacle in a general use space is not a code violation; however, it does decrease the number of available receptacles and could result in someone using an extension cord, which creates a risk of fire. When adding circuits to your home, ensure that you are using the correct type receptacle for the intended use of that circuit. For step by step instructions for wiring the receptacle, read our article on how to add an outlet to learn about the wiring process, from pulling the cable to doing the final test.
Beyond the Basic Duplex: Specialized Variations
Modern homes have specialized versions of the traditional duplex (double) receptacle (white or ivory with two square holes) for added safety, convenience and intelligence.
- GFCI Duplex Receptacles: GFCI outlets are used to help prevent electric shock in areas prone to moisture. (Bathroom, kitchen, outdoor, garage) GFCI outlets are designed with TEST & RESET buttons and continuously monitor the balance of electricity in the circuit. A GFCI duplex can also provide protection for receptacles installed on its load terminals.
- Tamper‑Resistant (TR) Duplex: According to NEC regulations for residential building construction, a tamper-resistant outlet has a trap door inside that closes when nothing but an equal amount of power is supplied. From a distance, these look very similar to regular outlets.
- USB‑Charging Duplex: This is a duplex receptacle which includes 1 or 2 USB-A or USB-C Connections combined with the two plug-in receptacles located in the centre of the receptacle and will eliminate the requirement of the bulky plug-in charging adapters, making them ideal for use in bedrooms, kitchens and home offices.
- Switch‑Outlet Combo: An electrical device combining a switch and a receptacle (or plug-in) in one space/double of a duplex. It is particularly convenient in an area where there is need for a switch and an outlet (such as in a bath) or location like a countertop in the kitchen.
Every one of these options is built upon a standard duplex form factor, so when you order a specialty outlet from GOG Electric, you are choosing an item that will fit perfectly in the same electrical box and standard duplex wall plate as a regular duplex device. When you are wiring a switch outlet combination device for your project, you can refer to our switch outlet combo wiring guide to get detailed instructions on how to correctly attach the wire terminals to the switch and the outlet.
Replacing an Old Duplex Receptacle: Practical Tips from the Field
The path that Sarah took to replace her kitchen outlet illustrates more common pitfalls when replacing an electrical outlet. After turning off the breaker and confirming the breaker was off with her voltage tester, she began unscrewing the existing device. When she removed the cover plate from the existing outlet, Sarah discovered that the connecting tab—the small brass bridge connecting the two hot terminals—was intact. The connecting tab allows power to both receptacles through the existing outlet. In some cases, the connecting tab has been broken off of the existing outlet, thus allowing for one receptacle to always have power and one receptacle to have power only when the wall switch is turned on (referred to as a ‘half-hot’ or ‘switched receptacle’).
If you replace an existing outlet that has been wired as two receptacles controlled differently, you must remove the connecting tab from your new duplex receptacle to mirror the existing wiring. Not recognizing this detail could lead to either creating an inoperable switch or creating a duplex receptacle that is always live. The wiring connections for a standard duplex receptacle are as follows: black wire connected to brass terminal, white wire connected to silver terminal, and bare wire connected to green terminal. Be sure to tighten all three terminal screws and tuck the wires neatly into the back of the electrical box before installing the new receptacle. Use a level when installing the receptacle; a crooked receptacle looks unprofessional and will not allow plug connections to be made properly.
Why GOG Electric’s Duplex Receptacles Are Built to Last
GOG Electric makes duplex outlets for everyday use that can take the abuse of removing and installing cords frequently, having objects apply force against them, and being exposed to cleaning solutions. Our standard duplex receptacles use thick gauge brass contacts for durability and grip force after thousands of inserts, nylon housings that won’t crack, and clear markings on the installation screws to allow for easy installation. We have all types of duplex configurations; standard duplex, tamper-resistant duplex, Ground Fault Circuit Interrupter Duplex, duplex with integrated USB ports, and duplex Switch/combo. All outlets are UL Listed and made to the same dimensional specification so that they will fit in standard wall plates and boxes without modification or alteration. When Sarah exchanged a single outlet for a GOG Electric tamper-resistant duplex, she sent us a picture of the completed job; a low, clean code-compliant installation that blends with her existing kitchen outlets. It’s what we design to do.
Frequently Asked Questions
What is the difference between a duplex outlet and a regular outlet?
A duplex receptacle is a common electrical outlet with two spaces for plug-in devices (the average person will refer to that type of outlet as a “regular outlet”). A true duplex receptacle gives you two receptacle openings mounted on one yoke, but a single receptacle (less common) consists of a single receptacle opening. When you buy a “standard outlet,” you will almost always be purchasing a duplex receptacle.
Is a duplex receptacle one outlet or two?
According to the national electrical code (NEC) definition, a duplex receptacle consists of two (2) separate devices, mounted to a single yoke, and counted as two (2) receptacle outlets as specified by the code’s rules on wall-space measurement standards. Many people incorrectly use the term “outlet” to describe the entire assembly when, in fact, the two (2) plug-in points make up the single outlet.
What does a duplex outlet look like?
On one flat plastic face of a duplex receptacle, there are two identical rows of receptacles that have their receptacle contacts arranged vertically. Each row has three holes: the narrow hot, the wider neutral, and the round ground; there is a single screw holding the wall plate to the receptacle housing. This type of outlet is the standard wall outlet that is installed in the majority of homes in North America. The receptacle that is single in construction differs from a duplex receptacle in that there is only one set of the three holes (contacts), and the face of the outlet may be primarily round or oval shaped.
What are the 4 types of outlets?
Most outlets can be divided into four functional categories: standard duplex receptacles (the typical two-plug outlets); GFCI outlets (outlets with ground-fault protection, identifiable by TEST and RESET buttons); AFCI outlets (arc-fault protection and less common as a receptacle type); and USB-charging outlets (standard or GFCI form factor outlets with USB ports). New construction requires tamper-resistant (TR) receptacles to be the mandated version of the standard duplex.
In general, when we think about an outlet we usually don’t have to think of exactly what type it is; however, when you go to buy a duplex receptacle, you will quickly learn that there are many different types of outlets (more than one). After reading through this blog, you should be able to identify a duplex receptacle as being an outlet with two plugs, how many outlets it counts as under code (two only), and what types of duplex receptacles are typically found in your local hardware store. There’s no question as to which duplex receptacle you should purchase once you understand that all GOG Electric duplex receptacles built are designed for ease of use and long-lasting durability. GOG Electric manufactures duplex receptacles from basic white tamper-proof model ™ to smart-ready USB charger for your convenience, and so your new outlet will hold strong for 10 years.
