NEC Article 220 — Load Calculations: The Complete Exam Guide

If there's one skill that separates passing electrician exam candidates from those who struggle, it's load calculations. Article 220 questions appear on virtually every journeyman and master exam, and they require more than just memorization — you have to work through numbers with your codebook open.

The good news: once you understand the structure of an Article 220 calculation, the process is repeatable. There are only a handful of tables and formulas you need to master, and this guide walks through every one of them.

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Article 220 Structure

Article 220 is divided into several parts:

• Part I (220.1–220.5): General rules — scope, voltages to use, rounding
• Part II (220.10–220.14): Branch circuit load calculations
• Part III (220.40–220.53): Feeder and service load calculations (Standard Method)
• Part IV (220.60–220.61): Feeder and service calculations — special conditions
• Part V (220.80–220.87): Optional calculation methods for dwellings
• Part VI (220.90–220.91): Optional calculations for schools and existing installations

Most exam questions pull from Parts II, III, and V.

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General Lighting Load: Table 220.12

Every load calculation starts with general lighting. NEC Table 220.12 lists the unit loads (in volt-amperes per square foot) for different occupancy types.

The values you need for the exam:

Exam tip: Dwelling units are 3 VA/sq ft. This is one of the most commonly tested values in all of Article 220.

How to calculate: Multiply the square footage of the applicable area by the unit load.

Example: A 2,000 sq ft dwelling unit general lighting load = 2,000 × 3 = 6,000 VA

Note: For dwellings, the floor area is calculated from the outside dimensions of the building. Unfinished spaces (not adaptable for future use) and open porches are excluded.

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Step-by-Step Residential Load Calculation (Standard Method)

Here's the standard method (NEC 220.40–220.53) applied to a typical dwelling unit:

Step 1: General Lighting Load (Table 220.12)

• 2,000 sq ft × 3 VA/sq ft = 6,000 VA

Step 2: Small Appliance Circuits (220.52(A))

• Two 20-amp circuits required by NEC 210.11(C)(1)
• 2 circuits × 1,500 VA each = 3,000 VA

Step 3: Laundry Circuit (220.52(B))

• One 20-amp laundry circuit × 1,500 VA = 1,500 VA

Step 4: Subtotal (Steps 1–3)

6,000 + 3,000 + 1,500 = 10,500 VA

Step 5: Apply Lighting Demand Factor (Table 220.42)

NEC Table 220.42 applies demand factors to the general lighting load plus small appliance and laundry circuits:

Applying to 10,500 VA:

• First 3,000 VA × 100% = 3,000 VA
• Remaining 7,500 VA × 35% = 2,625 VA
• Lighting demand total = 5,625 VA

Step 6: Fixed Appliances (220.53)

NEC 220.53: If four or more fixed appliances (other than dryers, ranges, A/C, or heating) are connected, apply a 75% demand factor to their combined load.

Example: Dishwasher 1,200 VA + disposal 900 VA + water heater 4,500 VA = 6,600 VA

• 3 appliances = no demand factor: 6,600 VA
• If 4+ appliances: 6,600 VA × 75%

Step 7: Dryer (220.54)

NEC 220.54: Use either the nameplate rating or 5,000 VA, whichever is larger, for a single residential dryer.

Example: 5,000 VA (minimum) or nameplate kW if higher.

Step 8: Range or Cooking Equipment (Table 220.55)

For a single household range rated over 8¾ kW, use Column C of Table 220.55 to find the demand load.

Example: 12 kW range → Column C = 8,000 VA demand

Step 9: Heating or A/C Load (220.60)

Use the larger of the heating or A/C load (they are considered non-simultaneous loads).

Example: 3-ton A/C at 3,600 VA; heating at 8,000 VA → use 8,000 VA

Step 10: Total Service Load and Ampacity

Sum all demand loads, then calculate the minimum service ampacity:

Total = 5,625 + 6,600 + 5,000 + 8,000 + 8,000 = 33,225 VA

Minimum ampacity at 240V = 33,225 ÷ 240 = 138.4 A → minimum 150-amp service

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The Optional Calculation Method: 220.82

NEC 220.82 provides a simplified approach for dwelling units. Many candidates find this method faster.

Step 1: Calculate the total load:

• General lighting: sq ft × 3 VA/sq ft
• Small appliance and laundry circuits: 1,500 VA per required circuit
• All appliances at nameplate or calculated values (ranges use Table 220.55 or 8 kW min)
• Heating or A/C (larger of the two)

Step 2: Apply Table 220.84 demand factors:

Example: 40,000 VA total load

• First 10,000 × 100% = 10,000 VA
• Next 30,000 × 40% = 12,000 VA
• Total demand = 22,000 VA
• At 240V: 22,000 ÷ 240 = 91.7A → 100-amp service minimum

Exam tip: The optional method often produces a lower calculated load than the standard method, which is why many practitioners prefer it. Both methods are code-compliant.

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Feeder Calculations for Multiple Dwelling Units: Table 220.42

When calculating feeders serving multiple dwelling units (apartments, condos), the general lighting demand factors from Table 220.42 apply to the total general lighting load for all units.

For electric ranges serving multiple units, use Table 220.55. The demand load per unit decreases significantly as the number of units increases — for example, 10 ranges at 12 kW each would not be calculated as 10 × 8 kW.

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Commercial Load Calculations

For commercial occupancies, the process is similar but uses the appropriate VA/sq ft from Table 220.12 and typically does not apply residential demand factors. Commercial loads must also account for:

• Show window lighting (220.14(G)): 200 VA per linear foot of show window
• Track lighting (220.43(B)): 150 VA per 2-foot section (or per linear foot as of NEC 2023)
• Sign loads (220.14(F)): Minimum 1,200 VA for each commercial occupancy

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Key Article 220 Tables to Tab

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Common Exam Mistakes on Article 220

1. Forgetting the 1,500 VA per small appliance circuit (not per outlet — per circuit)
2. Using the wrong demand factor table — Table 220.42 is for dwellings/multi-family; Table 220.44 is for non-dwelling receptacle loads
3. Not including laundry circuit in the Step 2 subtotal before applying Table 220.42
4. Range calculation errors — Table 220.55 has multiple columns and important Notes; read the Notes carefully
5. Not using the larger of heating or cooling — NEC 220.60 says to use only the larger load

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Ready to Practice Load Calculations?

Knowing the method is one thing — working problems under timed conditions is how you build speed for exam day. GetLicenseReady's practice questions include load calculation problems covering residential standard method, optional method, and commercial calculations.

Related reading: NEC Article 210 — Branch Circuits | NEC Article 430 — Motors | How to Pass the Electrician Exam on Your First Try