I am wiring a small workshop, using conduit. I was shocked to see how expensive THHN/THHW cable is, with respect to NM-B: at local big-box store, 100ft of 14/2 NM was $33, whereas 100ft of THHN was about $20 (so $60, almost double the price of NM, for 2 conductors plus EGC).

I am wondering about the pros and cons of using NM instead of THHN. Issues I see, for various options, are as follows:

  1. Just run exposed NM ? Probably against code, but it's just a detached shop and won't be inspected. I'm using conduit for outlets, but this is for lighting wiring in the ceiling, so out of reach; OTOH, it might be tempting to hang things on it. Probably a terrible idea.

  2. Run NM inside conduit ? Might be tough, due to its stiffness. OTOH, I'm using pretty big conduit (3/4" for just 2 14ga conductors plus EGC) and only two bends max.

  3. Pull the conductors out of the NM jacket and use these in the conduit ? How difficult would this be ? Don't want to have to rip the jacket the whole way, but once one conductor is pulled out (probably the EGC) the others should be easy. I've heard varying opinions on whether the wire inside the jacket of NM is actually THHN. I've read it doesn't have as "slippery" insulation, so doesn't pull as easily as real THHN. I've also read it's un-marked, so technically against code, but I probably don't care.

  4. Bite the bullet and pay much more for real THHN.

  5. Use armored cable such as MC or BX.

  • As an aside, it seems odd that a price that is presumably so commodity-driven (copper) would be so variable. Jul 23, 2018 at 18:46
  • 2
    Don’t forget armored cable as a possibility.
    – Tyson
    Jul 23, 2018 at 18:52
  • @Tyson Thanks for the idea. There seems to be two types of armored cable: BX is barely more expensive than NM; MC is $43 (for 100ft of 14/2). I need to research the differences between those two types. Jul 23, 2018 at 19:29
  • When used with metal conduit the conduit can be the ground, thhn is usually dual rated then also so it can be used in wet locations where NM is limited to dry locations.
    – Ed Beal
    Jul 23, 2018 at 19:30
  • Thanks for those points. However, this won't be a wet location. And I already decided to use a ground wire (when I did the outlets using conduit and THHN). I suppose I could do this ceiling lighting differently. Might be best to keep to the same methods though: thus arguing for buying NM and extracting the conductors. Jul 23, 2018 at 19:46

2 Answers 2


I pay $48-52 per 500ft for #12 THHN/THWN-2. I do not use #14 at all.

My preferred supplier is City Electric, and I shop around other proper electrical supplies, and Menards on 11% off days.

I do not buy ground wire because I use EMT properly, I use enough conduit clamps to hold it where it belongs, and I refrain from routing it unguarded in places at risk for damage or pullout.

When I find an odd situation where I worry about EMT parting, I dive into my junk drawer and find some old solid THHN or Romex that I had pulled out earlier, and strip down a bare wire of enough length to link the two junction boxes on either side of the danger zone.

By the way, I use stranded THHN/THWN-2. After the pleasure of working with stranded THHN/THWN in conduit, the idea of choking NM down a conduit is laughable.

You cannot strip the sheath off NM as a "cheap" way to get THHN. The reason is obvious once you work with the various wire types, but NM wire insulation doesn't even begin to compare to THHN insulation and it will too easily take damage. You are also relying on being able to strip sheath 100% perfect with no damage to either black or white insulation. It is also not marked, so it is not legal to use. And then you only have solid wire, which is more alligator wrestling.

The other big problem with shucking NM is you are stuck with only 2 wire color choices. I stock 9 colors of THHN and 10 colors of tape. If you're buying just a few rolls of THHN, consider colors other than white black red.

  1. I don't know whether running exposed NM is legal in your shop. Conduit is very convenient for lighting. Do not hang anything on electrical cables or conduit. If you want hangers for low voltage wiring or anything else, put them up there while you're up there.
  2. Your statements are inconsistent: one hand is hanging oversized conduit and running superfluous ground wires, the other hand is wringing over the cost of wire. Make up your mind. Either you're trying to save money or do a good job. I wire my lighting grids with 1/2" EMT and 2 THHN wires. Easy peasy.
  3. As mentioned, individual wires inside NM will get damaged if pulled through conduit.
  4. If THHN is much more expensive, you're sourcing at the wrong place. The big-box stores really getcha on small reels, and shamelessly overcharge on most other electrical parts too. (just not the ones you're likely to price-check). Big-box are not gods of pricing, or even selection; they are gods of being open at 9:30pm on a Saturday. They also have some freakish "Pied Piper" effect on consumers; it's almost impossible to convince folks to stop shopping at big-box.
  • 1
    I think I can answer the question as to why that pied-piper effect exists: your average electrical supply house isn't going to be open much (if at all) outside 9-5 working hours, meaning that it's going to be closed when the average DIYer is shopping, 99 times out of 100. (The one I've used is open for a few hours on Saturdays, but that's it.) Jul 23, 2018 at 22:26
  • Thanks @Harper for your thoughts. We have a City Electric and I like it. Not being a professional electrician though, it'd be silly for me to buy 500ft spools. It is wild though, the way per-foot price drops off with larger spools, especially for something where the price should be driven by a commodity. I agree with you about stranded THHN (used 12ga for my outlets). Jul 23, 2018 at 23:23
  • I'm not concerned with code, and I totally understand that you don't hang stuff on wiring. Somebody down the road might not though. So scratch option #1. Jul 23, 2018 at 23:25
  • I was unaware that the conductors within NM do not have as good insulation as THHN. Thanks for that info. Scratch option #3. Jul 23, 2018 at 23:26
  • 1
    I dont care about code either, I care about safety. However I am also a scrupulous researcher and every time I have seen a Code requirement that I thought was stupid, I gave it an honest look and found the requirement actually did serve safety and I had simply been unaware of all the considerations. The only ones I do not like are "AFCI everywhere", I feel wire in metal conduit is adequately protected by breaker and/or GFCI. Jul 23, 2018 at 23:35

Option 6: shop somewhere that is not going to rip you off on something as basic as 14AWG THHN.

Your intuition that NM and THHN should be priced similarly per wire-foot (length of cable * number of conductors in cable) is indeed correct -- the copper content is the main driver of the price of the finished product. (At an online supplier I use as a pricing reference, 14AWG THHN is 9 cents to the foot, while 14/2 W/G NM is 25 cents to the foot.)

So, we can conclude from this data that the big-box store is ripping you off on the THHN. As Harper suggests, an electrical supply house won't do that to you, so I would suggest finding one local to you and asking them for a price instead.

  • No, City Electric wants $70 for a 500ft roll of stranded 14ga THHN, whereas big-box has it for $45 (but based on Harper's quote above for 12ga, seems like CE is quoting me a mighty high price). Meanwhile, City Electric does not sell 100ft rolls. If I were a pro, or someone who uses as much as Harper seems to, I'd be happy with 500ft rolls, but I'll never use that much. So the $20 for 100ft at big-box doesn't seem so bad. But once you get below 500ft, apparently copper is not the main driver of price (which effect I've also seen on NM). Jul 24, 2018 at 18:33
  • Called a different City Electric location, quoting $64 and $40 for 12ga and 14ga, respectively (500ft of stranded THHN). After I asked if contractors get a lower price and got a slippery answer. But again, my main problem is that I have no use for 500ft rolls, and that's where the per-foot price gets reasonable. Jul 24, 2018 at 18:40
  • Yeah, it depends on the electrical supply, they have the oprion to charge you contractor prices, just they may be reluctant to if they think you're going to be a thousand-question wanting-to-return-everything hell customer. The latter belongs at Home Depot. I open by telling them I don't like big box prices nor their selection. That sets their expectation. Jul 24, 2018 at 21:44

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