NEC dwelling load — demand factors shrink the connected load
Your service is smaller than your appliances add up to: NEC demand factors reduce the connected load to the calculated load, which sets the service size.
What this diagram shows
A bar comparison of an NEC Article 220 dwelling load calculation. On the left, a tall stacked bar is the connected load — every appliance nameplate added up (lighting and circuits, electric range, dryer and water heater) totaling about 29,700 VA. In the middle, the NEC Article 220 demand factors: 100% of the first 10 kVA plus 40% of the rest, a 12 kW range counted as only 8 kW, and heating or cooling counted as the larger of the two. On the right, a shorter bar is the calculated load of 21,480 VA, which divided by 240 volts is 90 amps and rounds up to a 100 A service on 4 AWG copper.
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Electrical Load Calculator
What size electrical service do you need? Free NEC Article 220 load calculator — Standard or Optional method, minimum service amps and wire size.
