NEC Article 220: Branch Circuit & Feeder Load Calculations

NEC Article 220 provides the methods for calculating branch circuit, feeder, and service load requirements. It is one of the most important articles in the NEC because the load calculation determines the size of the service entrance, feeders, branch circuits, and overcurrent protective devices for an entire electrical installation.

Article 220 is organised into five parts:

• Part I (220.1–220.5): General requirements and definitions
• Part II (220.10–220.14): Branch circuit load calculations
• Part III (220.40–220.61): Feeder and service load calculations (standard method)
• Part IV (220.82–220.87): Optional calculations for dwellings and existing installations
• Part V (220.100–220.103): Farm load calculations

Two calculation methods are available: the Standard Method (Part III) and the Optional Method (Part IV). The optional method generally produces a smaller calculated load because it applies a single demand factor to the entire dwelling load, making it popular for residential service sizing.

Table 220.12 provides general lighting load densities in volt-amperes per square metre (VA/m²) or volt-amperes per square foot (VA/ft²) for different occupancy types. These are minimum values that must be used unless the actual connected lighting load is known and higher:

The general lighting load includes all general-use receptacles in dwelling units (Section 220.14(J)). This means the 33 VA/m² for dwellings covers both the lighting and the general-purpose 15A and 20A receptacle outlets.

After calculating the total general lighting load using Table 220.12, Table 220.42 applies demand factors that reduce the calculated load for feeders and services. Demand factors recognise that not all lighting will be on simultaneously:

The dwelling demand factor is particularly powerful. For a 2,500 ft² dwelling:

General lighting load = 2,500 × 3 = 7,500 VA

Demand factor (Table 220.42):
  First 3,000 VA at 100% = 3,000 VA
  Remaining 4,500 VA at 35% = 1,575 VA
  Total demand: 3,000 + 1,575 = 4,575 VA

Reduction: 7,500 → 4,575 VA = 39% reduction

A complete dwelling unit load calculation under the standard method (Part III) includes:

1. General lighting load: Floor area × 33 VA/m² (3 VA/ft²) from Table 220.12. This includes general receptacles.
2. Small appliance circuits: 1,500 VA per circuit, minimum 2 circuits required (Section 220.52(A)) = 3,000 VA minimum.
3. Laundry circuit: 1,500 VA for each laundry circuit (Section 220.52(B)).
4. Apply Table 220.42 demand factors to the sum of items 1–3.
5. Fixed appliances: If 4 or more fixed appliances (other than ranges, A/C, heating), apply 75% demand factor (Section 220.53).
6. Ranges and cooking equipment: Demand factors from Table 220.55 (Column C for ranges rated > 12 kW). One range = 8 kW demand.
7. Dryers: Demand factors from Table 220.54. One dryer = 5 kW or nameplate, whichever is larger.
8. Heating and A/C: Use the larger of heating or cooling load (Section 220.60 — non-coincident loads). Motor loads at 125% per Article 430.
9. EV charging: New NEC 2026 provisions for EV load management per Article 625.

Example: 1,800 ft² dwelling, electric range, dryer, 3-ton A/C, 40-gal water heater

General lighting: 1,800 × 3 = 5,400 VA
Small appliance: 2 × 1,500 = 3,000 VA
Laundry: 1,500 VA
                                 Total: 9,900 VA

Table 220.42 demand:
  First 3,000 at 100%: 3,000
  Next 6,900 at 35%:   2,415    = 5,415 VA

Range (Table 220.55): 8,000 VA
Dryer (Table 220.54): 5,000 VA
Water heater: 4,500 VA

Subtotal (3 fixed appliances < 4, no 220.53 factor):
  5,415 + 8,000 + 5,000 + 4,500 = 22,915 VA

A/C: 3 tons × 3,517 W × 1.25 = 13,188 VA
  (Heating not coincident — omitted)

Total: 22,915 + 13,188 = 36,103 VA

Service size: 36,103 / 240 = 150.4 A → 200 A service

Commercial load calculations follow the same general approach but with different demand factors and additional load categories:

Key differences from residential:

• No small appliance or laundry circuit minimums — only actual connected loads
• General lighting demand factors vary by occupancy type (Table 220.42)
• Receptacle loads: For non-dwelling occupancies, general-purpose receptacles are calculated separately at 180 VA per outlet (Section 220.14(I)), with demand factors from Table 220.44
• Kitchen equipment: Table 220.56 provides demand factors for commercial cooking equipment
• Motor loads: 125% of the largest motor plus 100% of all other motors (Section 220.50)
• HVAC: Calculated based on actual equipment nameplate ratings, with the largest motor at 125%

Table 220.44 — Receptacle demand factors for non-dwelling occupancies:

The optional method (Part IV, Section 220.82) provides a simplified calculation for dwellings that typically results in a smaller calculated load than the standard method. It is permitted for individual dwelling units with a single service or feeder.

The optional method works as follows:

1. Add all loads at 100%: General lighting (Table 220.12), small appliance circuits, laundry circuit, all appliance nameplate ratings, and all motor nameplate ratings.
2. Apply a single demand factor: First 10 kVA at 100%, remainder at 40%.
3. Add heating/cooling (largest): 100% of the larger of heating or A/C load.

Same 1,800 ft² dwelling as above:

Total connected load:
  General lighting: 5,400 VA
  Small appliance: 3,000 VA
  Laundry: 1,500 VA
  Range: 12,000 VA (nameplate, not demand)
  Dryer: 5,000 VA
  Water heater: 4,500 VA
                Total: 31,400 VA

Optional method demand:
  First 10,000 at 100%: 10,000
  Remaining 21,400 at 40%: 8,560
                        = 18,560 VA

A/C: 13,188 VA (same as before)

Total: 18,560 + 13,188 = 31,748 VA

Service: 31,748 / 240 = 132.3 A → 150 A service

Standard method: 200 A service
Optional method: 150 A service — one size smaller!