How This Calculation Works
The electrical load calculator adds up the wattage of all circuits and appliances in your home to determine total power demand. Each appliance draws a specific amount of power measured in watts.
Total watts are converted to amps using the formula: Amps = Watts ÷ Volts. For 120V circuits, divide by 120; for 240V circuits (dryers, ovens), divide by 240.
The NEC (National Electrical Code) requires that your main breaker panel handle at least 100% of continuous loads and 125% of non-continuous loads. Most modern homes need a 200-amp panel.
Common Mistakes to Avoid
- Forgetting 240V appliances. Dryers, ovens, and HVAC units run on 240V and draw significant power. Always include them.
- Not accounting for future growth. Plan for 20–30% headroom above current needs for future additions.
- Overloading circuits. Each circuit should not exceed 80% of its rated capacity for continuous use.
Worked Example
Scenario: A home with 10 general circuits at 1,500W each, plus a 5,000W dryer and 4,000W oven.
Step 1 — General circuits: 10 × 1,500 = 15,000W.
Step 2 — Large appliances: 5,000 + 4,000 = 9,000W.
Step 3 — Total: 15,000 + 9,000 = 24,000W.
Step 4 — Amps at 240V: 24,000 ÷ 240 = 100A. A 200A panel is recommended.