Residential Service Calculator

NEC Article 220.82 Optional Method

• Applicability: Single-family dwellings served by single 120/240V or 120/208V service
• Air Conditioning vs Heating: Include larger of A/C or heating load, not both (NEC 220.60)
• General Loads: First 10 kVA at 100%, remainder at 40%
• Ranges: Use NEC Table 220.55 demand factors (typically 8 kW for standard range)

Standard Service Sizes

• 100A Service: Minimum for modern homes, adequate for homes <2000 sq ft with gas heat/water
• 150A Service: Good for 2000-2500 sq ft homes with some electric appliances
• 200A Service: Standard for new construction 2500+ sq ft, all-electric homes
• 400A Service: Large homes (>4000 sq ft), extensive electric heating/appliances

Required Branch Circuits

• NEC 210.11(C)(1): Minimum 2 small appliance circuits (kitchen/dining)
• NEC 210.11(C)(2): Minimum 1 laundry circuit
• NEC 210.11(C)(3): Minimum 1 bathroom circuit
• NEC 210.52: Receptacle spacing requirements (6 ft/12 ft rules)
• GFCI/AFCI: Required in bathrooms, kitchens, garages, outdoors, bedrooms

Calculation Tips

• Square Footage: Use outside dimensions, include all floors except unfinished basements
• Future Expansion: Consider potential additions (hot tub, EV charger, pool)
• Electric Vehicles: Level 2 charger adds 40-50A load
• Solar PV: May require service upgrade for interconnection
• Resale Value: 200A service is standard for modern homes

Common Appliance Loads