Electrical Load Calculator
Residential Load Calculation
Simplified NEC residential load calculation
Total Appliance Load
Add up total connected load from appliances
Formula
General Load: 3 VA/sq ft | Demand: First 3000W at 100% + remainder at 35% | Service Amps = Total Demand / Voltage
Frequently Asked Questions
What is an electrical load calculation?
An electrical load calculation determines the total power demand of a building to size the electrical service (main panel), feeders, and branch circuits. It follows NEC Article 220 methods, applying demand factors to account for the fact that not all loads operate simultaneously.
What size service do I need for my home?
Most modern homes need 200A service. Smaller homes under 1,500 sq ft may use 100-150A. Larger homes with electric heating, EV chargers, or pools may need 300-400A. A load calculation per NEC Article 220 determines the exact requirement.
What is a demand factor?
A demand factor accounts for the fact that not all electrical loads operate at the same time. NEC provides specific demand factors: general lighting uses 100% for the first 3,000W and 35% for the remainder. Ranges, dryers, and HVAC have their own demand factors.
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