Size a single-family service with the NEC 220 standard method.
2 small-appliance + 1 laundry circuit included automatically.
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NEC 220 Part III standard method, 120/240 V 1-phase, 2 small-appliance + 1 laundry circuit assumed, fixed appliances at 100%. Simplified — verify the full calc.
Article 220 Part III lays out the standard method for calculating the minimum service or feeder size for a dwelling unit. The calculation starts with general lighting — 3 VA per square foot of floor area (NEC 220.12) — then adds mandatory branch circuit loads: two 20-ampere small-appliance circuits at 1,500 VA each and one laundry circuit at 1,500 VA (NEC 220.52). A demand factor is then applied to this subtotal: the first 3,000 VA is taken at 100%, and the remainder at 35% (NEC 220.42). This factor recognizes that not every general lighting and small-appliance circuit in the home operates simultaneously.
Electric ranges and cooktops follow the Column C demand table in Section 220.55 — a single unit rated up to 12 kW uses a 8,000 VA demand figure, scaling upward by 5% per kilowatt above 12. Electric dryers are sized at the nameplate rating or 5,000 VA minimum per Section 220.54. Fixed appliances such as water heaters are summed at 100% when fewer than four units are present. For heating and cooling, only the larger load is counted — they do not stack (NEC 220.60). Dividing the total calculated VA by 240 V gives the minimum service ampacity, which is then rounded up to the nearest standard panel size.
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