Commercial Load Build-Up Calculator

Build a commercial service load from the ground up across 13 occupancy types — stacking general lighting, receptacle, motor, HVAC, sign, and special loads with NEC Article 220 demand factors applied per category, with a load stack chart, what-if scenarios, load balance analysis, and calculation trace.

AVAILABLEAUTOMATED CHECKS ONLYSTANDARDS-AWAREINTERMEDIATENECWHAT DO THESE STATUSES MEAN?

NEC • ART. 22013 OCCUPANCY TYPESMOTOR + SIGN LOADSWHAT-IF SCENARIOS

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Overview

Commercial service load calculations are more complex than residential because NEC Article 220 applies different demand factors to different load types and occupancies — and a mixed-use building with office, restaurant, retail, and parking areas requires each area's loads to be calculated under the correct rules and then aggregated. This calculator builds the complete commercial load bottom-up. Select occupancy type (Office Building, Bank, Retail/Store, Restaurant, Warehouse, Manufacturing/Industrial, Hospital, Hotel/Motel, School/University, Religious Facility, Parking Garage, Workshop, or Mixed-Use with multiple areas), then add load entries by category: general lighting entries (VA/ft², square footage), receptacle entries (non-dwelling per 220.14(H), office/bank per 220.14(I)), motor entries (HP and FLC per Article 430), special receptacle entries, and for mixed-use buildings, additional area entries. NEC 2017 and 2020 editions are supported. The Results tab shows a load stack chart (connected vs. demand-adjusted per category), sizing basis, OCPD and conductor sizing context, and motor contribution calculation. The Trace tab walks every demand factor applied with NEC section citations including 220.14(F/H/I/K), 220.42(A), 220.43(A/B), 220.46(A/B), 430.6(A), and 600.5(A). The Verify tab runs validation checks and flags assumptions or warnings. A Load Balance Analysis section evaluates phase loading. A What-If Scenarios section allows toggling load inclusions to model alternative service sizes. Five named presets — Office, Retail, Restaurant, Industrial, and Motor — provide starting points. The NEC Reference Panel surfaces all active code sections. A Learn tab covers demand factor theory, load type distinctions, and a knowledge check quiz. Supports NEC 2017 and 2020.

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

Commercial Load Build-Up — Overview with Restaurant preset — Overview tab: Restaurant preset loaded at 3,500 ft² with lighting, receptacles, kitchen equipment, HVAC, and motor loads. Dashboard tiles show 99.2 kVA connected, 79.1 kVA calculated demand, and a 250 A service.

Commercial Load Build-Up — Calc Trace — Calc Trace tab: every demand factor walked step-by-step with the governing NEC 220 section cited — general lighting per 220.42(A), receptacles per 220.14(H)/220.44, kitchen equipment per 220.56, and the 125% largest-motor adder per 430.24/220.50.

Commercial Load Build-Up — Results with motor contribution — Results tab: motor contribution table shows FLC read from the NEC 460 V column and converted back at 208 V, plus the 430.24 feeder ampacity calculation grouped by voltage/phase and a plain-English calculation-notes list.

Commercial Load Build-Up — Proposed Design & What-If Scenarios — Proposed Design tab: sizing basis, MCA/MOCP echo, and the What-If Scenarios panel for toggling categories on/off to model alternate service sizes without editing inputs.

Commercial Load Build-Up — Code Refs — Code Refs tab: consolidated view of every active NEC section — 220.14(F/H/I/K), 220.42(A), 220.43(A/B), 220.44, 220.46(A/B), 220.56, 430.6(A), 430.24, and 600.5(A) — with the values as applied in the current edition.

Commercial Load Build-Up — Learn Mode — Learn tab: guided coverage of demand-factor theory, connected vs. calculated load, motor-contribution treatment, and a knowledge check to confirm you can defend the numbers on a plan review.

Commercial Load Build-Up — Office preset — Office preset: 1.3 VA/ft² general lighting from Table 220.42(A) with the 220.43 office/bank receptacle floor applied, contrasting with the restaurant occupancy so you can see how the same tool sizes very different services.

What you'll do

01Apply the correct NEC Article 220 demand factor for each commercial load category — general lighting (220.42), non-dwelling receptacles (220.14(H)), office/bank receptacles (220.14(I)), show-window lighting (220.43(A)), track lighting (220.43(B)), fixed motor loads, and sign outlets (600.5(A))
02Build a multi-category commercial load schedule for a single-occupancy and a mixed-use building and explain how each area's loads are calculated separately before aggregation
03Apply NEC 430.6(A) motor full-load current table values to calculate motor contribution to the feeder load, including the 125% continuous-load treatment of the largest motor
04Distinguish connected load from demand-adjusted load for a mixed commercial service and explain how demand factors reduce the required service conductor ampacity below the sum of connected loads
05Use the What-If Scenarios section to evaluate how removing or deferring specific loads affects the minimum service size
06Trace every demand factor applied in a completed load schedule to the specific NEC Article 220 section that governs it using the Calculation Trace tab

Try a guided scenario

Assemble a commercial occupancy load and watch ordering effects.

Commercial load buildup · NEC Calculation Practice

No sign-in required. Progress is saved on this device.

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).