Panelboard & Feeder Load Calculation

Build a multi-category panelboard or feeder load schedule with NEC Article 220 demand factors applied per category — general lighting, receptacles, kitchen, motors, HVAC, and more — then evaluate feeder conductor sizing and bus utilization.

AVAILABLEAUTOMATED CHECKS ONLYSTANDARDS-AWAREINTERMEDIATENECWHAT DO THESE STATUSES MEAN?

NEC • ART. 22015 LOAD CATEGORIESNONCOINCIDENT HVACBUS UTILIZATION CHECK

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Overview

Commercial panelboard and feeder load calculations are more nuanced than a simple sum of connected loads because NEC Article 220 applies different demand factors to different load categories — receptacles in office buildings get a 50% demand factor above 10 kVA, commercial kitchen equipment gets a further reduction, and noncoincident heating and cooling loads allow only the larger to be counted. Getting these category-specific rules right in a single spreadsheet is error-prone; this calculator applies each rule automatically as loads are entered. Add loads by category — General Lighting, Track Lighting, Show-Window Lighting, Receptacles (non-dwelling or office/bank), Dwelling Fixed Appliances, Non-Dwelling Fixed Equipment, Commercial Kitchen Equipment, Motors, HVAC (Cooling, Heating, Heat Pump, Supplemental Heat, Ventilation) — and the Results tab shows connected load, calculated demand load, and the sizing current side by side in a category breakdown chart. Set your bus rating to get a utilization gauge and warning if the sizing current exceeds the bus or main rating. Spare and future circuit capacity can be tracked as included in present demand, future/planning only, or excluded and shown separately. The Trace tab provides a step-by-step calculation citing every NEC Article 220 section applied. The tool covers system configurations from 120/240 V 1φ through 480 V 3φ delta and supports NEC 2017 and 2020 (2026 references are available but calculation is disabled pending full adoption). The Design Challenge tab generates panelboard sizing problems with evaluated results. A Self-Test tab verifies the calculation engine.

App preview

A live look at the app you'll launch — every control on the left drives the visualizations on the right in real time.

Inside the lab

Example data — not a real field report

Overview with panel load schedule — Overview — build a mixed-use panelboard load schedule (general lighting, receptacles, appliance, kitchen equipment, HVAC, motor) and the tool returns the calculated demand load per NEC Article 220 in real time.

Results and sizing — Results & Sizing — connected load vs. demand load vs. sizing load side by side, with the minimum feeder ampacity and the recommended standard OCPD per 240.6, plus a utilization gauge.

Step-by-step calculation trace — Calculation Trace — every demand factor printed line by line with citations to the specific NEC 220 section applied (220.12, 220.14(H)/(I), 220.42, 220.44, 220.56, 220.60), so each reduction is defensible in a plan review.

Design challenge mode — Design Challenge — randomized commercial panelboard scenarios (office, retail, kitchen, mixed-use) with your submitted feeder size graded against the correct answer and a diff of the demand factors that drove the result.

NEC code references summary — Code / References — every applicable NEC 2017/2020/2026 section summarized with the exact demand factors pulled from Tables 220.42, 220.44, 220.55, 220.56 for your inputs so the calculation is verifiable by hand.

Learn and scope — Learn & Scope — the distinctions between connected, calculated, and sizing load; when demand factors apply vs. when 100% is required; and an explicit list of what the calculator does not cover (dwelling-unit optional method, motor feeder 430 rules).

Deterministic self-test harness — Self-Test — a deterministic test harness runs the calculation logic against known-answer commercial panel scenarios so you can verify the tool matches worked examples in the NEC Handbook and textbooks.

What you'll do

01Identify which NEC Article 220 demand factor applies to each load category — general lighting (220.42), non-dwelling receptacles (220.14(H)), office receptacles (220.14(I)), commercial kitchen (220.14(J)), and fixed appliances (220.53) — and apply each correctly
02Explain the noncoincident load rule for HVAC systems under NEC 220.60 and determine which of heating and cooling is included in the feeder demand calculation
03Distinguish connected load, calculated demand load, and sizing current and explain why all three values are used in different parts of the design
04Set a bus rating and evaluate feeder sizing current as a percentage of bus capacity, identifying the NEC thresholds at which warnings apply
05Apply the correct demand factor for receptacle loads in office or bank occupancies under NEC 220.14(I) compared to general non-dwelling receptacles under 220.14(H)
06Trace every demand factor calculation in a mixed-use commercial panelboard load schedule to the specific NEC Article 220 section that governs it

What this lab is not

Not a design document, stamped calculation, or approval record.
Not a substitute for engineering analysis by a licensed professional.
Not a reproduction of NEC tables — values are computed and cited, and you must verify against the code edition enforced in your jurisdiction.
Not connected to live equipment and not a safety device.

Calculation basis

References NEC. Results are computed from the entered inputs and cited back to the referencing clause or table number — no code text or table is reproduced verbatim.

Simplifying assumptions are stated in the lab itself; where a model is intentionally conceptual, the lab says so rather than implying study-grade accuracy.

Standards basis: Standards-aware. Validation state: Automated checks only (last checked 2026-08-15).