Service Load Calculation (Residential)
Standard demand factors over lighting, appliances, range, dryer, HVAC; output minimum service ampacity.
Example
You enter
- Conditioned area (ft²) 2000
- Small-appliance circuits (min 2) 2
- Laundry circuits 1
- Fixed appliances total (W) 6000
- Range nameplate (W) 12000
- Dryer nameplate (W; 5000 minimum) 5000
- HVAC cooling (W) 5000
- HVAC heating (W) 8000
You get
- Total demand 32625 W
- Required ampacity 135.9 A
- Next standard service 150
Checked against published worked examples from: NFPA.
Details, formula, and sources
Formula or tableStandard method: general lighting and receptacle demand per NEC Table 220.45 (3 kVA at 100%, to 120 kVA at 35%, rest at 25%); range per Table 220.55 Column C; dryer per 220.54 (5 kW minimum when present); fixed appliances at 100% (the 75% of 220.53 needs an appliance count -- service-load-standard applies it); larger of heating or cooling per 220.60.
Source and editionNEC 2023 (NFPA 70). Article 220.
Free accessFree read-only access at nfpa.org/freeaccess.
What governsEstimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
API field namesarea_ft2, small_appliance_circuits, laundry_circuits, fixed_appliances_W, range_W, dryer_W, hvac_cooling_W, hvac_heating_W, total_demand_W, required_A, next_standard_A
- Voltage 240 V single-phase split for dwelling unless user suppliesANSI C84.1 nominal
- Demand factor for first 3 kVA general lighting 100% (per NEC 2023 Table 220.45)NEC 2023