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.
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
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
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