The Grading Scale: Breaking down confusing receptacle grades and subgrades

By Stephen Carr | Jun 15, 2022
Illustration of a socket with a smiling face and a sad face. Image by Shutterstock / Jim Larkin.
Recently, I was reading the wiring devices section of a specification. The requirement for receptacles was “commercial industrial specification grade, heavy-duty.” 




Recently, I was reading the wiring devices section of a specification. The requirement for receptacles was “commercial industrial specification grade, heavy-duty.” Even though I have seen this type of language before, this was the first specification I read that did not follow the requirement with a catalog number. I didn’t know which type of receptacle to put in my estimate.

I started working in this industry at a wholesale house in 1971. We sold a very simple selection of wiring devices. Our No. 1 seller was a Leviton 5320I, a residential-grade receptacle. We also carried some more expensive receptacles in Bryant and Arrow-Hart. These were specification-grade receptacles. The only significant changes to receptacles in the 1970s were new features, such as ground fault interrupting and surge suppression.

When I started working for electrical contractors, we had three choices: residential, commercial and specification grades. Hospital-grade receptacles were introduced a little later. I became aware of one more grade of receptacle when I purchased a new house about 30 years ago: the “it should be illegal.” Anything I plugged into them just fell out. I imagine they were a counterfeit product with a fake UL label.

Before I continue, I would like to qualify what is important to me as an electrical estimator when it comes to wiring device grades: cost. I acknowledge that some types of wiring devices may have labor-saving features. However, it is more important to meet the requirements of the specifications when selecting wiring devices to put in an estimate. You would not want to put $1 receptacles in your estimate, and then end up being required to install $15 receptacles in the project.

Grades and subgrades

Here is a list of words I currently see referred to as wiring device grades in electrical specifications: residential, commercial, construction, specification, industrial and hospital. After a lot of research, it turns out some of these terms can be descriptive or marketing terms. One manufacturer’s representative told me they are aware of the confusion the large number of descriptions are causing, and they were working to simplify their offerings. He also said they were consolidating grade categories because of the economy of scale.

Let’s try to simplify this. Depending on who you ask, there are four or five grades: residential, commercial, industrial, specification and hospital. Some manufacturers consider the hospital-grade to be an optional feature of their industrial-grade receptacle. There are also subgrades, such as heavy-duty and extra-heavy-duty. Within each of those grades are many options, including ground fault interruption, surge suppression, isolated ground and how wires are attached to a device.

What’s the deal with all these descriptions?

Another source of confusion remains as many manufacturers use the same catalog number for wiring devices of different qualities. Let’s look at the 5362 receptacle, which has been referred to in project specifications as a specification-grade receptacle for as long as I have been an estimator. I checked the websites of several manufacturers and found the following: Hubbell describes it as commercial/industrial grade, Leviton describes it as an extra-heavy-duty industrial receptacle, Legrand calls it a hard-use specification-grade receptacle and Eaton calls it a heavy-duty industrial-specification grade receptacle. Just to make it a little more confusing, some manufacturers add a prefix that modifies the description. Add “HBL” in front of a Hubbell 5362, and you get an industrial extra-heavy-duty specification-grade receptacle.

So, what’s the deal with all these grades and subgrades? They are about the quality and capability of the wiring device. Residential-grade wiring devices don’t have to be very tough. In our homes, we tend to plug things in and leave them. If we knock a plug out of a receptacle at home, it is a minor inconvenience. If a plug gets knocked out in a hospital bedroom, someone could die.

There are industry specifications on how the various grades of receptacles must perform. Hospital-grade, one of the toughest receptacles, is subjected to contact stressing, assembly security testing, abrupt plug removal testing and impact testing. After the stress testing, the receptacle is tested for ground contact temperature rise, resistance and fault current. All this testing is done to very high standards.

If you are bidding a project with many wiring devices, it is important to make the right selections for your estimate. I checked Trade Service for pricing information for a 5362W and found prices ranging from $4.11 to $9.73 in the average market price column. If the requirements for your estimate are vague, ask for clarification, or qualify your proposal for which wiring devices you are including.

Header image by Shutterstock / Jim Larkin. 

About The Author

CARR has been in the electrical construction business since 1971. He started Carr Consulting Services—which provides electrical estimating and educational services—in 1994. Contact him at 805.523.1575 or [email protected], and read his blog at

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