Calculate residential electrical service size per NEC 2026 Article 120. Supports both Standard and Optional calculation methods with NEC 310.12 conductor sizing.
Based on NEC 2026 Article 120, NEC 310.12
Professional Verification Required: All calculations are for reference and estimation purposes only. Results must be verified by a licensed Professional Engineer (PE), licensed electrician, or qualified person before use in any installation, design, or permit application.
Reference: NEC 2026 Article 120*Input Nameplate Ratings (VA or Watts)
Dwelling units: 2 VA per square foot of living space.(reduced for LED adoption)
Only the larger of heating or cooling load is included.
100% of first 8 kVA, 40% of remainder, plus 100% HVAC.(threshold lowered)
Residential service conductors sized at 83% of rating.
EVSE calculated at 100% nameplate. Continuous load 125% factor no longer applies to load calculation.
IMPORTANT LEGAL DISCLAIMER
For Reference Only: This calculator is provided for educational and informational purposes only. It is not intended to be a substitute for professional engineering design, advice, or certification.
Code Compliance: Calculations are based on the 2023 National Electrical Code (NEC®). However, local codes, amendments, and Authority Having Jurisdiction (AHJ) requirements vary by location and may supersede standard NEC requirements.
Verify with Your AHJ: Local Authority Having Jurisdiction (AHJ) requirements take precedence over all general code references. Contact your local building department or electrical inspector to confirm applicable codes, amendments, and permit requirements before beginning any electrical work.
No Liability: SparkShift, LLC and its affiliates assume no liability for errors, omissions, or the use/misuse of this tool. Users are solely responsible for verifying all results against applicable codes and standards before installation. Always consult a licensed electrician or Professional Engineer (PE).
NEC Reference: NEC 2026 Article 120, NEC 310.12
© 2026 SparkShift, LLC. Calculations are for reference only.
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