NEC Article 220 Service Load Calculator
A spreadsheet-grade Article 220 service and feeder load calculation with Residential and Commercial templates, itemized through five categories, with a live running total and a button that exports the finished table into a Revit drafting view.
What it calculates
- Residential template: dwelling-unit general lighting plus 220.52(A)/(B) small-appliance (2×1,500 VA min.) and laundry (1×1,500 VA min.) circuits, Table 220.55 Column C range demand, dryer demand VA, and the 220.82 optional-method total for comparison against the standard method
- Commercial template: general lighting by Table 220.12 occupancy unit load, Table 220.44 receptacle demand (first 10 kVA at 100%, remainder at 50%), and Table 220.56 kitchen-equipment diversity for 3+ units
- Both templates: fixed/specialty equipment load, and mechanical/HVAC load with 220.60 non-coincident grouping plus the 430.24 largest-motor 125% rule
- Total connected load, total demand load, demand amperes, and a recommended standard service size
Typical inputs
- Residential or Commercial template selection
- Occupancy type and floor area, or a manual connected-VA override
- Service voltage and phase
- One row per load item: description, quantity, rating, and unit (VA / amps / kW / HP)
Known limits
- Verified end-to-end for one scenario (Retail/Mercantile, Commercial template) — see the screenshots on the overview page. The Residential template and multiple non-coincident HVAC groups are not yet separately validated.
- The exported drafting-view table is authored at view scale 1; changing the view's scale afterward makes the table no longer true paper size.
Frequently asked
Is there a separate calculator for residential vs. commercial load calculations?
No — one tool, two templates. Switching the template changes which Article 220 method and demand tables apply (220.52/220.55/220.82 for Residential, 220.12/220.44/220.56 for Commercial) without leaving the calculator.
Why calculate both the standard and optional residential methods?
The optional method (220.82) is simpler and often gives a lower service size, but it only applies to dwelling units meeting specific criteria. The Residential template runs both, so you can confirm you're allowed to use the optional result before relying on it.
Does the Service Load Calculator work for residential (dwelling unit) projects?
The calculator supports the dwelling-unit path in code (220.52 small-appliance and laundry circuits are folded into the general lighting category per 220.14(J)), but that path has not yet been run end-to-end inside Revit the way the commercial scenario has — treat it as unvalidated until confirmed against a known-good calculation.
What does the exported table actually contain?
A drafting view named "SYMATEQ - SERVICE LOAD CALCULATION" with an itemized table matching the on-screen categories — connected load, demand factor and demand load per line, plus the totals and recommended service size — ready to drag onto a sheet.
Autodesk and Revit are registered trademarks of Autodesk, Inc. SYMATEQ is not affiliated with, endorsed by, or sponsored by Autodesk, Inc. SYMATEQ Electrical Calculators is an independent add-in for Autodesk® Revit®. Calculations are engineering aids and do not replace review by a licensed professional engineer or confirmation with the authority having jurisdiction.