NEC dwelling load calculator (Article 220)
Enter the floor area and the major loads of the dwelling, and we show the load per NEC Article 220 with the standard and the optional method, with the working line by line, the suggested service size and conductor. An informative calculation; NEC mode is in beta.
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What does the load calculator compute?
The service load of a single-family dwelling according to NEC Article 220, with two methods side by side:
- Standard method: general lighting at 3 VA/sq ft (220.41), 1500 VA for each small-appliance and laundry circuit (220.52), demand factors (220.45: first 3000 VA at 100 %, 3001–120,000 VA at 35 %, the rest at 25 %), 75 % for four or more fixed appliances (220.53), the dryer at 5000 VA minimum (220.54), cooking equipment per Table 220.55, and the larger of heating and air conditioning (220.60).
- Optional method (220.82): the first 10 kVA at 100 %, the rest at 40 %, with heating and air conditioning per 220.82(C).
For both methods the result is the total load in VA, the current at 240 V, the suggested service size (100, 125, 150 or 200 A) and the matching copper conductor (310.12). The interface uses the article numbers of the 2023 NEC.
Worked example: 1500 sq ft, 12 kW range, 5.5 kW dryer
| Item (standard method) | VA |
|---|---|
| General lighting, 1500 sq ft × 3 VA | 4,500 |
| Two small-appliance and one laundry circuit, 3 × 1500 VA | 4,500 |
| Subtotal | 9,000 |
| With demand factors: 3000 + 6000 × 35 % | 5,100 |
| Range, 12 kW (Table 220.55) | 8,000 |
| Dryer | 5,500 |
| Total | 18,600 |
18,600 VA / 240 V = 77.5 A, so the suggested service is 100 A. The calculator shows the same working line by line, with the data you enter.
What it does not compute
The calculation is simplified: the neutral load (220.61) and 25 % of the largest motor are not included, and there is no suggestion above 200 A. It is an informative calculation, not a permit document: the service size is decided by the authority having jurisdiction (AHJ) and the NEC edition in force, and the values must be checked against the official text. The program's NEC mode is in beta.
Automatically in the drawing
In an NEC project the same calculation on the boards page takes its inputs from the drawing (the area is the sum of the rooms) and also compares the load center's main breaker against it. See the US electrical plan page.
Frequently asked questions
Which method's result should I use?
The calculator shows both, with the optional method (220.82) first. Which one applies to your plan is the designer's decision, according to the authority having jurisdiction (AHJ) and the NEC edition in force.
Does it include the neutral and motor loads?
No. The neutral load (220.61) and 25 % of the largest motor are not included; calculate them separately.
What does it give above 200 A?
The suggested service is 100, 125, 150 or 200 A; for a larger load the calculator gives no suggestion, and a custom design is needed.
Related pages
- US electrical plan (NEC) – the load calculation from the drawing
- Power and current converter – in NEC mode for 120, 240 and 208Y/120 V
- Electrician calculators – all calculators
- NEC conduit fill calculator – EMT és PVC csövek töltése
- NEC box fill calculator – a doboz szükséges térfogata
- NEC service upgrade calculator – EV-töltő, klíma, mért terhelés
In detail in the tutorial
- Designing to the NEC (USA) – dwelling load calculation on the boards page