What actually changed in the NEC 2026

Most of the NEC 2026 is the same as the 2023 — we compared Table 310.16 cell by cell from 8 AWG all the way to 2000 kcmil and found zero differences. What did change is concentrated in a few places: the small-conductor rows at the top of Table 310.16, the article letters in 250.122, and a handful of table numbers. The renumbering is the part most likely to bite you, because an old article number still lands on a real article — just the wrong one.

Table 310.16 changed for real, not just cosmetically

The ampacity table people actually use every day picked up two new rows and lost one. Everything from 8 AWG down through 2000 kcmil is untouched, so if you work mostly in feeder and service sizes, nothing here affects your numbers.

240.4(D) grew an entry to match

The small-conductor overcurrent list went from seven entries to eight. The new one covers 14 AWG copper-clad aluminum at 10 A, and it carries conditions: a continuous load at or below 8 A, and overcurrent protection from a device marked as supporting that conductor size or from specific fuse classes.

This and the new Table 310.16 row are two halves of the same change. Neither one stands on its own — the conditions live in 240.4(D), and no calculator can verify them for you, because it cannot see your load profile or read the marking on your breaker.

10 A is a standard breaker rating now (since 2023, not 2026)

This one trips people up because it is often filed under 2026 changes when it actually landed in the 2023. In the 2017 and 2020 editions the standard rating list started at 15 A and 10 A appeared only in the supplementary fuse list. From 2023 onward, 10 A is the first entry of the main list, and the supplementary fuse list no longer carries it.

250.122 letters shifted — and the old letter is now a different subject

This is the change most likely to cost you time, because nothing errors out. You look up the article you have always looked up, you land on a real article, and it is about something else.

One clarification worth noting: the 2026 wording spells out that upsizing driven by ambient temperature correction or conductor bundling adjustment does not trigger the proportional EGC increase. That was already the accepted reading from 2020 onward; the 2026 just stops leaving it to interpretation.

Table numbers that moved

• Box fill volume allowance is Table 314.16(B)(4) in the 2026. Older references point at (B)(1). The seven rows of values are unchanged between 2023 and 2026.
• The box fill section now runs through 314.16(B)(6), which brings terminal blocks and similar devices into the itemized count. Earlier editions stopped at (B)(5).

One thing that is not a change, but is widely gotten wrong

EMT does not stop at trade size 4. Article 358.20(B) puts the maximum at trade size 6, and Chapter 9 Table 4 lists dimensions for both 5 and 6 inch EMT in the 2023 and the 2026 alike, with identical values. We know this precisely because we had written a data-integrity check that assumed a 4 inch ceiling — it flagged correct data as corrupt until we checked it against the printed text.

So what should you actually do

1. 1

   Check what your jurisdiction adopted

   Adoption runs on its own schedule, state by state. Plenty of work in 2026 is still being inspected against the 2020 or the 2023. The edition your AHJ enforces is the one that matters, not the newest one published.

2. 2

   Re-check any article numbers you have memorized in 250.122

   That is the one place where muscle memory sends you to a wrong-but-real article.

3. 3

   Leave feeder and service sizing alone

   From 8 AWG up, the ampacity values are identical to the 2023. There is no need to redo work that was correct last year.

AmpRule is not affiliated with or endorsed by NFPA. NEC and National Electrical Code are trademarks of the National Fire Protection Association. Always verify against the edition adopted by your AHJ.