Dwelling Load Calculations in the 2026 NEC — Article 120 Standard and Optional Methods
This is where the Calculations portion earns its name: 8 of the 30 scored Master calculation items and 4 of 24 Journeyman items sit in "Services … Load Calculations," and the Residential Wireman exam leans on it too. Everything below is from the 2026 text, and several numbers changed from 2023 — old worksheets will give wrong answers.
NFPA 70 National Electrical Code, 2026 edition · Reviewed 2026-09-19
This is where the Calculations portion earns its name: 8 of the 30 scored Master calculation items and 4 of 24 Journeyman items sit in "Services … Load Calculations," and the Residential Wireman exam leans on it too. Everything below is from the 2026 text, and several numbers changed from 2023 — old worksheets will give wrong answers.
1. Housekeeping rules — 120.5 to 120.7
- Nominal voltages to use: 120, 120/240, 208Y/120, 240, 347, 416Y/240, 480Y/277, 480, 600Y/347, 600 (120.5(A)).
- Fractions of an ampere: below 0.5 drop it; 0.5 and above round up (120.5(B)).
- Floor area: outside dimensions; for dwellings, exclude open porches, detached garages, and unfinished spaces not adaptable for future habitable use (120.5(C)).
- 2026 change — 120.5(E): load calculations do not multiply continuous loads by 125%. The 125% still applies when you size the conductors and OCPD (210.19/210.20, 215.2/215.3, 230.42(A)), but not when you compute the load.
- Noncoincident loads (120.6): where two loads can't run at the same time, use only the larger (the A/C-versus-heat rule).
- Power control systems (120.7, new): a listed PCS per Article 130 may cap the calculated load; the controlled loads are taken at the PCS setting, which must be ≤ 80% of the OCPD rating; non-controlled loads are calculated normally.
This is where the public part ends.
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