Dwelling Load Calculator — NEC 220 Standard & Optional
Free · works offline · no account · NEC 2023 tables
Service sizing for one-family dwellings, both ways the code allows: the standard method with its per-category demand factors, and the 220.82 optional method most electricians actually use for 100 A+ services. OhmBase shows the full walk-through and compares the two results.
Open the free calculator →How the math works
Standard method: general lighting at 3 VA/sq ft plus 1,500 VA per small-appliance and laundry circuit, taken through the Table 220.42 demand factors (first 3 kVA at 100%, the rest at 35%), plus range demand from Table 220.55, dryer per 220.54, fixed appliances per 220.53, and the larger of A/C or 65% of central heat (220.60). The optional method (220.82) instead takes ALL general loads at nameplate, applies 100% to the first 10 kVA and 40% to the remainder, then adds the larger of heating or cooling.
1,800 sq ft dwelling · 2 small-appliance circuits · 1 laundry circuit (standard method, lighting loads only)
- General lighting: 1,800 × 3 = 5,400 VA
- Subtotal with circuits: 5,400 + 3,000 + 1,500 = 9,900 VA
- Table 220.42 demand: 3,000 + (6,900 × 0.35) = 5,415 VA.
FAQ
- Standard or optional method — which should I use?
- Whichever gives the smaller service, as long as its conditions are met. The optional method (220.82) requires a one-family dwelling with a 100 A or larger service, and usually wins once there’s electric cooking or heat.
- Does the calculator handle ranges over 12 kW?
- Yes — the standard method applies the Table 220.55 note: the Column C demand increases 5% for each kW the nameplate exceeds 12 kW.
- Is this calculator a substitute for a permit-ready load calc?
- It computes per the NEC 2023 tables, but your AHJ has the final word — always verify against the currently adopted code in your jurisdiction.