Complete Guide to NEC Lighting Load Calculations
The Lighting Load Calculator computes general lighting VA per NEC 220.42 with demand factors. Essential for service sizing, panel schedules, and code compliance.
NEC 220.42 General Lighting Loads
Dwelling Units: 3 VA per sq ft
Other Buildings: Table 220.42 (e.g., 3.5 VA/sq ft for offices)
Demand Factors (Dwelling Units)
| First 10,000 VA | Next VA | Demand % |
|---|---|---|
| 0–10,000 | — | 100% |
| 10,001–120,000 | — | 35% |
| >120,000 | — | 25% |
Other Building Types (Table 220.42)
| Type | VA/sq ft |
|---|---|
| Office | 3.5 |
| Store | 3.0 |
| School | 3.0 |
| Hospital | 2.0 |
Branch Circuit Requirements
- 15A Circuit: 1,440 VA max (120V × 12A)
- 20A Circuit: 1,920 VA max (120V × 16A)
- 80% continuous load rule (NEC 210.19)
Example: 2,500 sq ft Home
- Gross VA = 2,500 × 3 = 7,500 VA
- Demand = 100% of 7,500 = 7,500 VA
- Branch Circuits = 7,500 / 1,440 ≈ 6 × 15A
Commercial Example: 10,000 sq ft Office
- Gross VA = 10,000 × 3.5 = 35,000 VA
- No demand factor for non-dwelling
- Total = 35,000 VA
Fixed Lighting & Receptacles
Add actual wattage of fixed lighting (recessed, track). General receptacles often included in lighting load for non-dwelling.
Panel Schedule Tips
- Balance lighting across phases.
- Use 20A circuits for LED efficiency.
- Document in panel directory.
Common Mistakes
- Forgetting demand factors.
- Using actual LED watts instead of VA/sq ft.
- Mixing dwelling and non-dwelling rules.
- Ignoring outdoor lighting.
Advanced Applications
- Energy Code: Title 24, IECC limits
- LED Retrofits: Lower actual load, same NEC VA
- Smart Lighting: Occupancy sensors reduce demand
- Service Upgrade: Include in total load
Standards & Codes
- NEC 220.42: General lighting
- NEC 210.23: Branch circuits
- IECC: Energy efficiency
Conclusion
Accurate lighting load ensures code compliance and proper panel sizing. Our Lighting Load Calculator applies NEC demand factors instantly. Pair with Load Balance and Breaker Size tools. Build smarter with 1000 Calculators.