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NEC Art.220
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How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact NEC Art.220 reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
A dwelling load calculation tells you how big a service or feeder a home needs by adding up its electrical loads and applying the demand factors the NEC allows. Get it wrong and you either oversize the service and waste money, or undersize it and fail inspection. This app runs the full NEC Article 220 calculation — including the popular 220.82 Optional Method — and shows every line so you can hand the result to an inspector.
The NEC 220.82 optional method
For a single dwelling the optional method is faster than the standard method and usually yields a smaller, legal service. It works in three parts:
- General loads — 3 VA per ft² of living area, plus 1500 VA for each of the two required small-appliance circuits and the laundry circuit, plus the nameplate rating of every fixed appliance (water heater, dishwasher, disposal, dryer, range, and so on).
- Demand factor (220.82(B)) — take the first 10 kVA of that total at 100% and everything above 10 kVA at 40%.
- Heating or cooling (220.82(C)) — add the larger of the air-conditioning load or the heating load, never both.
Worked example — 2,000 ft² home
General lighting: 2,000 ft² x 3 VA = 6,000 VA. Small-appliance and laundry: 3 x 1,500 = 4,500 VA.
Appliances: water heater 4,500 + dishwasher 1,200 + disposal 900 + dryer 5,000 + range 12,000 = 23,600 VA.
Sum of general loads = 6,000 + 4,500 + 23,600 = 34,100 VA. Apply 220.82(B): first 10,000 at 100% = 10,000, remaining 24,100 at 40% = 9,640. Subtotal = 19,640 VA.
Add the larger of A/C (5,000) or heat (10,000) = 10,000 VA. Total = 29,640 VA / 240 V = 123.5 A → a 125 A or 150 A service.
The app handles the standard method (220.42 lighting demand factors) as well, and lets you toggle between NEC 2023 and NEC 2026 to see how the updated demand factors change the result.
Related calculators
Once you have the service size, pick the feeder with the wire size calculator and protect it with the breaker size calculator.
Electrical load FAQ
Which method does the calculator use?
Both. It runs the NEC 220.82 Optional Method for single dwellings (first 10 kVA at 100%, the remainder at 40%) and the standard Part III method with the 220.42 lighting demand factors, so you can compare the two.
What loads have to be included?
General lighting at 3 VA per square foot, the two small-appliance circuits and the laundry circuit at 1,500 VA each, and the nameplate rating of every fixed appliance such as the water heater, dishwasher, disposal, dryer, and range.
How is the service size in amps found?
Divide the calculated demand in VA by the service voltage (240 V for a standard residential service), then round up to the next standard service size such as 100, 125, 150, or 200 amps.
Does it support NEC 2023 and 2026?
Yes. You can switch between the 2023 and 2026 editions instantly to see how the updated demand factors affect the result, and every line shows the article it comes from.
Does it work offline?
Yes, the calculator runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
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