Electrical Load Calculator

About this calculator

Sizing a home's electrical service follows the logic of the NEC Standard Method for dwelling load calculations: general lighting load is figured at 3 VA per square foot of living area, small-appliance and laundry circuits add fixed VA allowances, and large fixed appliances (range, dryer, water heater, HVAC) are added at their nameplate ratings — with demand factors applied to the total, since not everything runs at once. Dividing the resulting total VA by the service voltage gives the required amperage.

This calculator takes a home's floor area, lighting load, and appliance load and returns the total electrical load and service current. Electricians use this calculation to determine whether an existing panel (commonly 100A or 200A) has enough capacity for a renovation or new appliance circuit, and home inspectors and electrical engineers use the same method to verify that a service upgrade is properly sized before signing off on a permit.