Construction
Service Load Calculator (NEC 220)
NEC 220 Part III standard residential service calculation. 100A vs 200A vs 400A — get it right before the wire goes in.
Service size (A @ 240V)
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- Total load (kVA)
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- After demand factor
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- Minimum amps
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FAQ
Standard vs optional method? +
Standard method (220 Part III) is conservative. Optional method (220.82) gives a smaller answer for most homes. AHJ may require either.
Why is 100A often not enough? +
EVs, heat pumps, and induction ranges push modern homes past 100A. 200A is the new minimum for most new construction.