Electric Safety: 4 Common Mistakes Using Extension Cords

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Electric Safety: 4 Common Mistakes Using Extension Cords
Article updated 11/28/2023

Electrical cords and extension cords are common everywhere.

From homes to the workplace, they are one of the most commonly used and most likely abused tool that we have.

Often utilized for simple things like plugging in the space heater at work or stringing decorative lights during holidays, the easiest option for consumers is to go online or to the nearest hardware section of a store and purchase an inexpensive cord. If the price, length of cord and type of connector meet our needs, we will likely purchase the item and not think anything else about it.

Choosing an extension cord is more involved than that.

Plan ahead before buying an extension cord. Know what it will be used for and where it’s going to go. It’s also important to know how much power the equipment you’ll be plugging into it uses.

IEEE Informational Paper

IEEE has an informational paper that describes what to do and NOT to do with electrical equipment cords and extension cords.

Here are a few examples:

  • DON’T plug extensions cords together.
    • Get one that is the correct length you need. It may be tempting to just string them together, but resist the temptation. Extending the length of an extension cord by “daisy-chaining” can lead to overheating the cord by overloading it, creating a serious fire hazard.
  • DON’T exceed the rating of the cord.
    • This is a common mistake in offices that allow space heaters. All extension cords have wattage limits, and these limits must be respected. Again, you are looking at a fire hazard if the cord is overloaded. Some of the cheaper extension cords use internal wiring that is size 16 gauge, rated for only 10 amps. A typical 1500 watt space heater draws 12.5 amps, obviously overloading a 16-gauge extension cord. To be safe, plug the heater directly into the wall and skip the extension cord or power strip altogether.
  • DON’T allow the cords to become a trip hazard.
    • Spending a little extra up front on a cord that is longer but able to be stored out of the way of foot traffic is better than having someone injure himself or herself because of tripping over the cord. However, do not use metal staples or nails to secure a temporary power cord.
    • Keep in mind that the National Electrical Code does not allow extension cords in lieu of permanent wiring (NEC 400.8(1) – 2014 Version). See this OSHA section (specifically 1910.305(g)(1)(iv)) for other restrictions as well as the following OSHA interpretation letter for more guidance. Another good interpretation letter can be found here.

And my personal favorite:

  • DON’T use extension cords to connect wires in the attic or above suspended ceilings/ANYWHERE.
    • These are just accidents waiting to happen. A common violation is found in the installation of ceiling-mounted electrical equipment like projectors in training and meeting rooms (as in the following photo). These locations must have a receptacle mounted flush with the ceiling with the unit’s power cord visible at all times.


See IEEE’s complete list.


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Ken Sellars

Ken Sellars is an instructor of electrical safety, NEC, Grounding/Bonding and Arc Flash Safety courses nationwide. Read more about Ken.

This Post Has 43 Comments

  1. Liko

    Thank you. Just the information I was searching for.

    1. Ken Sellars

      You are welcome. I’m glad we could be of assistance!

      1. Karen

        Hi i just moved into a friend of mines house..im making the attic as comfortable as i can for now there is no electric in attic but theres 2 seperate outlets in kitchen right outside the stairs leading to the attic can i run an orange drop chord from outlet and hook a power surge to it to plug a few different things in and then could I take another orange drop cord and run it from a separate Outlet in the kitchen up there with separate power surge plugged in to it will that work if not what do you suggest cuz there’s no way getting around adding any electrical up there I just want to make sure I do this in a safe way

        1. Hugh Hoagland

          That is a job for an electrician. Code requires permanent wiring to be installed by a qualified person according to the National Electric Code. This is also state law in every state. Using temporary cords for permanent purposes are one of the most common ways houses burn down.
          Thanks for asking. Keep your home safe!

        2. Ken Sellars

          This arrangement is not recommended. There is a commonly-cited electrical code violation that goes something like this, “You cannot use extension cords in lieu of permanent provisions for power.” Such an arrangement invites a failure and a subsequent fire, especially when going from one room to another, like kitchen to attic. Extension cords should only be used temporarily, and immediately put away when not in use. This way they are attended while in-use and are not left plugged in. An unattended cord has been the cause of many fires and electrocutions over the years. For temporary use, certainly use an extension cord, but once the task is complete, it is best to unplug it and store it properly…and of course, ALWAYS inspect the cord before use, ensuring ground pins are intact, no cuts or nicks or in the insulation, and no other issues exist. One more recommendation – always use GFCI protection when using extension cords. You can purchase in-line units that provide GFCI protection that can be stored with the cord when not in use.

      2. brian

        Ken, can 2 extension cords connected together (daisy chain) be used temporarily? does OSHA prevent this say for like an hour or so?

        1. Ken Sellars

          Any daisy chaining of cords will violate their listing per UL 817. Here is a direct quote from an OSHA interpretation letter: “The employer must follow all marked warnings and limitations associated with that cord, including a warning contained on a tag affixed to the cord that provides, “Do not plug one extension cord into another.” If an employer disregards such a warning tag, it would be using the cord in a manner outside of its intended application. This would be a violation of 29 CFR 1926.403(b)(2).” Obviously if you are using an extension cord at home, you are not subject to OSHA rules, but in the workplace, ignoring instructions on included documentation, including listing and labeling instructions, qualifies as an OSHA violation. Basically, if you need a longer cord, the only correct answer is to purchase a longer cord that has been listed/labeled for that distance. As the article states, this avoids overheating issues from voltage drop, and allows full rated amperage at the user-end of the extension cord.

  2. Danielle

    Hello there! Is it ok to plug an extension cord in a power cord?

    1. Ken Sellars

      If you are asking if it is okay to plug one extension cord into another extension cord, the general answer is that it is not a good idea. Each cord length has a specific ampere rating based upon the cord’s internal wiring size and distance of those wires. If you add another in-line, you could easily exceed the allowed or desired voltage drop on the circuit, causing a lower-than-standard voltage on the receptacle-end of the cord. This could result in a low supply voltage to the device being utilized, and this condition could cause equipment failure and present a fire hazard as well. It is recommended to always purchase the length of cord that is needed for your application, and then be sure to not overload the cord. The rating is required to be included on the cord per the listing agency’s mandate. I always recommend that you purchase the largest-size cord that you can afford to minimize effects of voltage drop and to be able to provide the most wattage as safely possible on the receptacle end. By following this practice, the equipment being utilized will last longer and you will minimize unnecessary risks of fire. And do not forget to use GFCI-protection on the SUPPLY end of your extension cord – a critical link in the electrical safety chain!

  3. Debbie Keys

    I’m looking for clarification/interpretation of the National Electrical Code’s prohibition of use of extension cords in lieu of permanent wiring (NEC 400.8(1) – 2014 Version). I do not see the referenced OSHA interpretation letter. How is “permanent wiring” defined?

    1. Ken Sellars

      My sincere apologies. Somehow the links either disappeared from the article or were overlooked when the article was released. Either way, they are now restored. The most important restriction is listed in OSHA 1910.305(g)(1)(iv) and states (partial quote):

      Unless specifically permitted otherwise in paragraph (g)(1)(ii) of this section, flexible cords and cables may not be used:
      As a substitute for the fixed wiring of a structure;
      Where run through holes in walls, ceilings, or floors;
      Where run through doorways, windows, or similar openings;
      Where attached to building surfaces;
      Where concealed behind building walls, ceilings, or floors; or
      Where installed in raceways, except as otherwise permitted in this subpart.

      To be specific to your question, the idea or definition of “permanent wiring” is referred to in 400.8 of the 2014 NEC as “fixed wiring,” referring to the previous “Uses Permitted” section in 400.7. Basically, if you have uses OUTSIDE of 400.7, then flexible cords or cables should NOT be used in this application. Anything outside of these allowances would have to be approved by your Authority Having Jurisdiction, which usually would be the city/county/state electrical inspector, or the Federal version of this on any Federal properties. To be transparent, the term “permanent” is not well defined in the NEC, but the wording “fixed wiring” is intended to mean normal building wiring, as in conductors in raceways, cable trays, or building cable designed for that purpose. I hope this clears things up a little. If not, please let me know.

  4. Hilton Homes

    Your tips are very helpful! It was so informative and it really does help people especially since a lot of people tend to plug extension cords together! Thanks for this information.

    1. Ken Sellars

      It is critical to stay on top of electrical safety, even with things like extension cords and power strips. Thanks for your kind comments.

  5. Tim

    If one complies to all the safety recommendations associated with use of extension cords, why is it unsafe to run an extension cord in the attic?

    1. Ken Sellars

      In general, all cables have heat restrictions and overall use restrictions. Attics can get very hot, and extension cords may not be rated for this type of heat, which could cause the cable insulation to break down prematurely and would be a fire risk. Also, you must look at the manufacturer’s use restrictions in accordance with its listing and labeling and only use extension cords per the manufacturer’s allowance. One more point – an extension cord is never meant to be used in the place of permanent wiring provisions. The idea of a cord is for temporary power only. If I am using one in an attic, it sounds as if a receptacle should be permanently installed near the equipment needing the power. This is a much safer installation in general.

  6. Jonathan

    what if i’m hooking up an alarm device like this, https://www.amazon.com/gp/product/B0006BCCAE/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1 , https://www.amazon.com/BINZET-Transformer-120V-130V-Convertor-Regulator/dp/B00JRX360W/ref=pd_rhf_ee_p_img_14?_encoding=UTF8&psc=1&refRID=2CTJNQFBZKWG47PD4BDN . I was planning on having it hooked up to a back up battery source in the garage (upc) for security reasons but was gonna have an extension cord connecting them. Is there any other way? I don’t think its a good idea to put a backup battery in the attic, but that seems like the only other option. would that be safe?

    1. Ken Sellars

      Extension cord is not the answer. You can get rated wiring for this at any electrical supply store. Ask for security/fire alarm wire and they can give you a 2-wire cable made just for this purpose. Run this from your UPS DC output to your alarms. This will be a code-compliant installation.

  7. Jonathan

    I appreciate that information, Thank you


    Hello. Can you plug an extension cord into a water cooler? Where is there a definition of “portable” to determine whether those bottled water machines delivered are considered portable/ Thanks

    1. Hugh Hoagland

      The reasoning for NOT using an extension cord is fire and voltage drop. While the water cooler is “technically portable”, you are not moving it around and plugging and unplugging the cord regularly. In that case it should be a permanent plug. This eliminates two possible failed connections that could cause shock or fire over time.

      If it is being moved, be sure the cord is adequately protected and that it can carry the current. The goal of the NEC is to prevent shock and fire (NFPA is primarily a firefighter’s organization).

  9. David

    I want to run a small device in my attic, using 2 Watts or less. Would a power strip or extension lead still be unwise? I can’t think of any other way to power it.

    1. Hugh Hoagland

      This is not allowed via the NEC. I would never do this since it is a potential fire hazard IF the power strip fails. According to NFPA, failed power strips are one of the number one causes of house fires. The best way is to a licensed electrician install a plug or direct wire the device. Anything in the attic is heavily stressed due to temperature changes and should be VERY high quality and designed for that use.

  10. Richard W Dyer

    Hey Hugh,

    Great article but I still have a question. Working construction, in a large building, is it daisy chaining to use a short GFCI plug (12-18 inches) between a non-GFCI building outlet and an extension cord that is being used to power HEPA air scrubbers, lights, fans, and or power tools? Also, I read in the HEPA air scrubbers add on Amazon that because there is a fuse or GFCI inside the scrubber, they can be daisy chained. Is this true? If so then can a GFCI line cord be used between more than one extension cord?

  11. Joe Dirt

    This article is written and rules like this were put into place to get the NECA contractor’s more work. Plain and simple. If you really worked construction and knew the actual challenges and didn’t just sit at a desk and think of ways to get more work for your members, you would know this. There is nothing wrong with plugging two extension cords into each other as long as the load and voltage changes are considered while doing it. We are qualified and certified professionals on the job. To say you can only use one extension cord is nonsense.

    1. Ken Sellars

      Joe, we are not involved with NECA (although I highly respect them as an organization), so I am not sure where that comment comes from. I have in fact worked construction for many years, and was a licensed electrical contractor for many years. I still hold a Master’s Electrical license just in case I ever have to go back to my tools. I have worked industrial, military, utility, and commercial electrical work, in construction, maintenance, repair – just about all facets of the electrical trade. By you stating that you are “qualified and certified”, and then continuing on to say that you can plug one extension cord into another, you may want to consider important things like product listing/labeling requirements, and the National Electrical Code section 110.3(B), which requires people to follow listing/labeling requirements. UL 817 is the standard for evaluating cord sets and power supply cords, or what we call “extension cords.” The idea of daisy-chaining directly violates one of the required markings on such cords, that is required to state, “Do not plug one extension cord into another.” By doing so, one directly violates this instruction, and this fact has been proven on many OSHA inspections, resulting in direct citations. No one is questioning an electrician’s or engineer’s ability to not overload a cord, but that is simply not all of the picture.

  12. Jimbo

    Ok I have a brinks timer with one single plug can I use an extension with this to power 2 lights ? Tungsten says 1250 w thanks .

    1. Ken Sellars

      It depends on several things: Is the timer rated for that high of a load? If the lights are 1250 watts each, that is over 20 amps on a 120 volt circuit. Most likely the Brinks timer you have is only rated to a max of 20 amps, and that is probably not continuous amps. Also, you cannot use temporary cords, like extension cords, in lieu of permanent provision for power. If this is a temporary install, in certain circumstances you would be allowed to use a temporary cord. OSHA has several rules in regards to extension cords, as does the NEC. It would be good to review these in detail to get further clarity on extension cord allowances. See OSHA 1910.305 and NEC chapter 400.

  13. Ellie

    I am trying to run a cord from on outlet on a southern wall to a western wall and need outlets at 2 locations on the western wall. The total length required is 15ft and I need outlets at 15ft and at 10 ft. How can I achieve this safely? I’m trying to avoid plugging extension cords or surge protectors into one another.

    1. Hugh Hoagland

      Hire a qualified electrician. This is the right way for anything not temporary.

    2. Ken Sellars

      Is this a temporary install, or permanent? Be careful not to use extension cords as a replacement for proper permanent wiring. This is a violation of the National Electrical Code, and if in the workplace, also violates OSHA electrical requirements. Your question leads me to believe that you need actual receptacles installed by a licensed electrician (if permanent). If this is a temporary situation as defined in the NEC, Article 590, then flexible cables like extension cords may be used. Companies do make Y-adapters that are made for the situation you describe. You can plug one cord into the wall for supply, and then plug in your required cords for temporary loads. Be careful to purchase only listed adapters (called Power Taps in the UL Listing) and use the items within their amperage and voltage limitations.

  14. LittleE

    I live in a newish mobile home and an electrician just installed a new GFCI outdoor outlet for me with a bubble cover. From there, I ran a brand new extension cord (outdoor light duty 16 Gauge/13AMP) to the backyard and connected two very small low voltage LED outdoor floodlights. This is such a small draw that I hope it’s OK to plug in the two outdoor lights into the 3-outlet end of the extension cord. I am trying to learn about residential electrical. Halloween and Christmas light time is coming up and I need a website with info on how to do this right.

  15. Internet Cabling Auckland

    You will get clear details from the article on the 4 common mistakes while using the extension cords. I really loved it and thank you very much for sharing this article with us. You have a great visualization and you have really presented this content in a really good manner.

  16. Henry

    Mr. Sellars,
    Thank you very much for your article and responses.
    We have a tenant running extension cords (daisy-chained) into an egress stair into the garage then over (being supported) by electrical conduits and other MEP elements to charge his electric vehicle.
    Many red flags. Tripping hazard and the other dangers mentioned in your article.
    I am trying to find references that the UBC (Uniform Building Code) and NFPA that address the potential hazards of this tenant’s actions.
    Any assistance you can lend will be much appreciated.

    1. Ken Sellars

      Glad to help. Sorry for the delay. There are definitely several things violated here. Daisy chaining directly violates the UL listing of extension cords, which in turn automatically violated the NEC section 110.3(B) which states, “Installation and Use: Equipment that is listed, labeled, or both shall be installed and used in accordance with any instructions included in the listing or labeling.” On the UL listing, the instructions should specifically state, “DO NOT PLUG ONE EXTENSION CORD INTO ANOTHER.” By violating this, the user has created a fire hazard, introduced possible excess voltage drop, and definitely endangers building occupants. On this alone, I would require the cord to be removed. Another issue is the typical statement that electrical inspectors use, and it goes like this: You cannot use extension cords in lieu of permanent provisions for power.” In other use, if I need a receptacle, I need to install a receptacle. Finally, the NEC has a specific article covering EVs, and it requires a specific dedicated receptacle for each EV. This is in Article 625 of the National Electric Code, and 625.40 states that each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit, and that circuit can have no other outlets.” By charging his EV on a set of extension cords, plugged into a general purpose outlet, he is potentially overloading the circuit and again creating a fire hazard. The only good solution is to install a dedicated 120 volt 20 amp circuit for this purpose. I hope this helps your situation.

  17. Scarborough

    These are very good tips. I was reminding a coworker to day about this and now I’m going to email this article to him for yet another safety reminder. He deserves it!

  18. Joseph Carroll

    Can an electrical plug from a piece of equipment (in this case a carpentry say) be “Taped” to the plug of an extension cord to prevent the plug from being unplugged? Also, could this be interpreted as a form of daisy chaining as the saw probably should be plugged directly into an outlet?

    1. Ken Sellars

      Hello Joseph. As far as taping an extension cord plug to a piece of electrical equipment, the question arises as to why the extension cord is being used. The idea of an extension cord is to use that cord for temporary use, as in plug it in, use it, and when that activity is complete, put the extension cord away. There is a favorite phrase used by many inspectors that goes like this on the citation, “Extension cord used in lieu of Permanent Provision for Power.” I call it the 3-P rule. In other words, if I use an extension cord and it is taped in place, tie-wrapped in place, or secured by plastic staples, etc., I am possibly using that cord outside of its intended purpose. Again, plug it in, use it, and when the job is complete, stow the cord in its proper place.

      There is nothing that prevents the user from taping the cord in place to prevent dust/dirt from entering, but my suspicion as an inspector would be that the user needs to install a receptacle for that machine. Another item to be aware of is the equipment listing and labeling. If that equipment makes any statement similar to “unit must be plugged into a wall outlet,” then the use of an extension cord is technically a violation of equipment listing/labeling, which by default makes it a violation of the National Electrical Code and OSHA (in the USA). All equipment must be used in accordance with its listing and labeling.

      As for the cord itself, always read and follow the instructions on the tag. It probably says something like this: “A cord set not marked for outdoor use is to be used indoors only. Inspect thoroughly before use. Do not use if damaged. See product label for specific wattage. Do not plug more than specified number of watts. Do not run through doorways, holes in ceiling, walls or floors…the list goes on and on showing on the required tag on the listed cord. One of those bullets is this: “ALWAYS UNPLUG WHEN NOT IN USE.” This statement is required to be followed per its listing. If I tape an extension cord to equipment and leave it plugged in, that most certainly violated the intent of use of the manufacturer.

  19. Sue

    I’d like to stack my washer and dryer since the laundry room is just too small with the dimensions of the appliances (front loaders). Therefore I need to put them to another spot in the laundry room. Doing that – the power cord for the washer is about 3 feet too short. The Samsung power cord has a clip at the end and the longest I get this cord is the one that’s on the machine (5 feet). So I think my only option is to use a short extension cord (even when I read everywhere not to use an extension cord). Or what option do I have other than the extension cord?
    Any thoughts – recommendations?
    Any idea why Samsung does not produce longer power cords if we should not use an extension??

    1. Ken Sellars


      Extension cords are meant as a temporary solution, and should be used as such. The answer is to have a receptacle installed at the new location for your appliance – in this case, your washer. You can purchase heavy duty extension cords that would certainly handle the load of a washer, but often, manufacturers will state in the instructions to plug directly into a wall outlet. Following such instructions maintain warranty requirements and ensure that electrical products are used within their designed safety limits. As a good rule of thumb, you should never use an extension cord in lieu of permanent provision for power. In other words, if you need a permanent solution, install a code-compliant receptacle that is within reach.

      Abuse of extension cords is a very common cause of house and business fires every year across the world. I would, however, contact Samsung and see if they offer any better solutions. It is worth an email or phone call to find out.

  20. Frank

    Simple can you daisy chain multiple GFCI cords?

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