Article 120 in the 2026 NEC provides the requirements for branch-circuit, feeder, and service load calculations. And like many articles in the NEC, it has a “Part 1. General.” Articles that have a Part 1. General start off with Section 1 Scope. The verbiage here is a bit difficult to visually take in, but the chart that is the Figure for Informational Note 120.1 makes the layout of Art. 120 easy to see. Right below that Table 120.4, which provides references for specific-purpose calculation requirements that are not in Chapters 5, 6, or 7 or that amend or supplement the requirements of Art. 120. For example, if you’re installing fixed resistance heaters the table directs you to Sec. 425.4.
The five subsections of Sec. 120.5 pertain to the actual calculations:
(A) Voltages. Unless other voltages are specified, use the ones listed here (e.g., 120, 120/240, 208Y/120, etc.).
(B) Fractions of an ampere. You can round to the nearest whole ampere and drop decimal fractions smaller than 0.5.
(C) Floor area. Calculate from the outside dimensions of the building. For dwelling units, specific structures (e.g., porches) are not included.
(D) Direct current loads. You can use the dc equivalent (e.g., VA in place of W).
(E) You are not required to calculate continuous loads at 125%.
If you have non-incident loads you can use the single largest of those loads when calculating the total load [Sec. 120.6]. For feeders and services, these can be loads that are unlikely to be used at the same time. For branch-circuits, feeders, or services, these can be loads that are prevented from running at the same time.
The general requirements of Art. 120 end with those for Power Control Systems (PCS) [Sec. 120.7]. Because a PCS is a type of energy management system, it must comply with Art. 130, Part II [Sec. 120.7(A)]. Part II is entitled, “Power Control Systems (PCS).” And it also has a “General” section [Sec. 130.50]. At first blush, this looks like all of the general requirements should be in one place or the other. But the general requirements in Art. 120 are for load calculations using a PCS. They are not general requirements for PCS. What the “General” in Sec. 130.50 says is that Part II contains additional requirements for PCS.
