Enter your Building Square Footage, appliance ratings (Range, Dryer, Water Heater), HVAC Load, and circuit counts to find your Minimum Service Size — the amperage your service entrance needs. You'll also get a breakdown of Calculated Load, Lighting Load, Appliance Load, and Demand Factor.
Minimum Service Size
--
Calculated Load
--
General Lighting Load
--
Appliance Load
--
HVAC Load
--
Yes, NEC Article 220 requires load calculations for service entrance sizing and panel load determinations. This ensures electrical safety and code compliance for residential installations.
Load calculations determine maximum simultaneous demand based on NEC requirements, not actual usage. The calculation includes safety factors and considers worst-case scenarios that rarely occur in real life.
Connected load is the sum of all electrical equipment ratings. Calculated load applies NEC demand factors and diversity factors to determine the actual expected maximum demand on the electrical system.
The optional method (NEC 220.82) can only be used for single-family dwellings and individual dwelling units with specific conditions. It often results in smaller service sizes than the standard method.
Only include electric appliances in your load calculation. Gas appliances (gas range, gas dryer, gas water heater) should be entered as 0 VA since they don't contribute to electrical load.
NEC requires continuous loads to be calculated at 125% of their rating for conductor and overcurrent protection sizing. This accounts for loads operating for 3 hours or more continuously.
Yes, EV chargers are considered fixed appliances and must be included in load calculations. They typically range from 3.8kW (Level 2) to 11.5kW for residential installations.
Diversity factors are already built into NEC demand factor tables. Additional diversity between panels may be considered by engineers but should follow local code requirements and engineering judgment.