Residential Load Calculation Cheat Sheet for the Master Electrician Exam

Residential load calculations are a staple of the Texas Master Electrician exam. The standard method outlined in NEC Article 220 is what you need to know.

Step 1: General Lighting Load

Multiply the dwelling square footage by 3 VA per square foot (NEC Table 220.12).

Example: 2,500 sq ft × 3 VA = 7,500 VA

Step 2: Small Appliance and Laundry Circuits

Add 1,500 VA for each of the two required small appliance circuits, plus 1,500 VA for the laundry circuit.

Total: 3 × 1,500 = 4,500 VA

Step 3: Apply Demand Factors

Combine the general lighting load and small appliance/laundry loads, then apply the demand factors from NEC Table 220.42:

• First 10,000 VA at 100%
• Remainder at 40%

Example: 7,500 + 4,500 = 12,000 VA total

• First 10,000 VA = 10,000 VA
• Remaining 2,000 VA × 40% = 800 VA
• Demand total: 10,800 VA

Step 4: Add Fixed Appliances

Add the nameplate ratings of all fixed appliances. If there are 4 or more fixed appliances (other than ranges, dryers, and HVAC), apply a 75% demand factor.

Step 5: Add Range and Dryer Loads

Use NEC Table 220.55 for ranges and Table 220.54 for dryers. A single household range is typically calculated at 8,000 VA. A dryer is typically 5,000 VA.

Step 6: Add HVAC Load

Compare the heating and cooling loads. Use the larger of the two (NEC 220.60).

Step 7: Calculate Service Size

Divide the total VA by 240V to get the minimum amperage.

Practice this calculation method repeatedly. It will appear on your exam.