Intermediate
NEC Demand Factor Formulas
NEC 220 demand factor formulas — residential lighting, range, dryer, and commercial kitchen equipment demand calculations.
Formulas
Lighting: first 3,000 VA @ 100% + remainder @ 35%
NEC Table 220.42 — dwelling unit lighting/receptacle demand
Range ≤ 12 kW: use 8 kW demand
NEC Table 220.55 — household cooking equipment
Range > 12 kW: 8 kW + 400W per kW over 12
NEC Table 220.55 — ranges over 12 kW
Dryer: 5,000W or nameplate (whichever larger)
NEC 220.54 — household dryer
4+ fixed appliances: 75% of total
NEC 220.53 — fixed appliance demand
Variable Definitions
VA=Volt-amperes (apparent power)(VA)
kW=Kilowatts (real power)(kW)
Worked Example
2,000 sq ft home: general lighting + 2 small appliance + 1 laundry circuit.
- General lighting: 2,000 × 3 VA/ft² = 6,000 VA
- Small appliance: 2 × 1,500 = 3,000 VA
- Laundry: 1 × 1,500 = 1,500 VA
- Total: 10,500 VA
- Demand: first 3,000 @ 100% = 3,000 + remaining 7,500 @ 35% = 2,625
- Demand total = 5,625 VA
Answer: 5,625 VA demand (from 10,500 VA connected)
When to Use
- •Residential service load calculations (NEC 220)
- •Determining minimum service size
- •Commercial kitchen equipment demand reduction
- •Sizing feeders and transformers
Standards & References
- NEC Table 220.42 — Lighting Demand Factors
- NEC Table 220.55 — Range Demand
- NEC 220.53 — Fixed Appliance Demand
- NEC 220.54 — Dryer Demand