NEC Load Calculation for Residential Service (NC Adopted Code)
Calculate the minimum electrical service size for a residential dwelling using the NEC Standard Load Calculation method (Article 220) as adopted by North Carolina (2020 NEC / NCEC).
General Lighting & Receptacle Load
Small Appliance & Laundry Circuits
Fixed Appliances (enter nameplate VA or watts each)
Dryer
NEC 220.54: Use nameplate or 5,000 VA minimum, whichever is larger. Demand factor 100%.
Cooking Equipment
NEC Table 220.55: Demand factor applied based on nameplate kW rating.
Heating & Cooling (Largest Load — NEC 220.60)
Only the larger of heating or cooling is used (NEC 220.60). Heat pump: use compressor + supplemental heat per 220.60.
Service Voltage
Formulas & Method (NEC Article 220 — Standard Calculation)
- General Lighting Load (NEC 220.12 / Table 220.12):
VA = Floor Area (sq ft) × 3 VA/sq ft - Small Appliance Circuits (NEC 220.52(A)):
VA = Number of Circuits × 1,500 VA (minimum 2 circuits) - Laundry Circuit (NEC 220.52(B)):
VA = Number of Circuits × 1,500 VA (minimum 1 circuit) - Demand Factors — Lighting + Small App + Laundry (NEC Table 220.42):
First 3,000 VA @ 100% + Next (up to 120,000 VA) @ 35% + Remainder @ 25% - Fixed Appliances (NEC 220.53):
If ≥ 4 appliances: Total VA × 75%; if < 4: Total VA × 100% - Dryer (NEC 220.54):
Demand VA = max(Nameplate VA, 5,000 VA) × 100% - Cooking Equipment (NEC Table 220.55, Column C):
≤ 8.75 kW: use nameplate; 8.75–12 kW: 8,000 VA; >12 kW: 8,000 + 400 VA/kW above 12 - Heating / Cooling (NEC 220.60):
Use the larger of total heating VA or total cooling VA (non-coincident loads) - Total Load:
Total VA = Lighting Demand + Fixed Appliance Demand + Dryer Demand + Range Demand + HVAC Demand - Minimum Service Ampacity:
I (Amps) = Total VA ÷ Voltage (240V standard)
Assumptions & References
- Based on 2020 NEC (NFPA 70) as adopted by North Carolina (NC Electrical Code).
- Uses the Standard Load Calculation method per NEC Article 220, Part III.
- Floor area excludes open porches, garages, and unfinished spaces not adaptable for future use (NEC 220.12).
- Minimum 2 small appliance branch circuits (NEC 210.11(C)(1)) and 1 laundry circuit (NEC 210.11(C)(2)) are required.
- For heat pumps with supplemental electric heat, enter the total combined VA of compressor + supplemental heat in the heating field, per NEC 220.60.
- NC requires a minimum 100-ampere service for new single-family dwellings (NEC 230.79(C)).
- This calculator does not account for electric vehicle charging (NEC 625), solar/battery systems, or optional calculation methods (NEC 220.82–220.87).
- Always verify with the local Authority Having Jurisdiction (AHJ) and a licensed NC electrical contractor.
- References: NEC 2020 Articles 210, 220, 230; NC Building Code Council electrical amendments.