Panelboard & Feeder Load Calculation

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.

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

• 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