Residential Load Calculator
Engineering Specification Sheet
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Generated: August 10, 2026
Residential Load Calculator
Size a dwelling service by the NEC 220.82 optional method — and see what the same house calculates under the 2026 code, where the article moved and two of the numbers changed.
Dwelling & Loads
Optional Method (220.82) — Article 220
This is the method most residential work uses: it applies to any dwelling served by a single 120/240 V or 208Y/120 V 3-wire service of 100 A or larger, and it usually yields a smaller service than the Standard Method. The Standard Method (Article 220 Part III) is not offered here — see the note below.
At 3 VA/ft² under NEC 2023 = 6,000 VA. Measured from outside dimensions; open porches, garages and unfinished spaces not adaptable for future use are excluded.
1,500 VA each per 220.82(B)(2). NEC 210.11(C)(1) requires at least two small-appliance circuits in every dwelling.
220.82(B)(3) takes these at full nameplate rating — no per-appliance demand factor. That is what makes the Optional Method simpler than the Standard Method, which would demand-factor cooking appliances through Table 220.55.
220.82(C) takes the largest of these, never the sum — heating and cooling are noncoincident loads. Add every system you have and the calculator picks the one that governs.
Why there is no Standard Method here
The Standard Method demand-factors cooking appliances through Table 220.55, and we could not verify that table against two independent published sources — one reproduction we found even prints it in the wrong shape, giving a percentage per range where the code gives a kilowatt value. We would rather ship one method we can stand behind than two where one is guessed. The Optional Method is also what most residential service and panel-upgrade work uses.
Service Size
93.1% of the service used
Under NEC 2026 this house calculates 108.0 A
— the same service size, but a different calculated load. NEC 2026 reorganised Article 220 into Article 120, cut general lighting from 3 to 2 VA/ft², and cut the 100% tier from 10 kVA to 8 kVA. Check which edition your jurisdiction has actually adopted before you quote.
Derivation
Calculations based on NEC 2023 guidelines. Results are for estimation purposes — verify against local code before installation.
Verified against NEC 2023 · 220.82, 220.82(B), 220.82(C), 230.79(C)
Subpanel & feeder schedule
Feeding a subpanel from the service above? These four numbers are the whole feeder spec. They come from the same engines as the Wire Size, Breaker Size and Conduit Fill calculators, so this schedule and those pages cannot disagree.
Your calculated service is 125 A; a subpanel feeder must not exceed it, and the sum of everything the service feeds still has to work.
| Feeder conductorsNEC 310.16 · 110.14(C) | 3 × #3 |
|---|---|
| Equipment grounding conductorNEC Table 250.122 | 1 × #8 |
| Feeder overcurrent deviceNEC 240.6(A) | 100 A |
| Minimum racewayNEC Ch. 9 Table 1 & 4 | 1" |
#3 copper carries 100 A at a 75°C termination, 30°C ambient, 3 current-carrying conductors. Raceway sized for 4 conductors (0.329 in²) — the neutral counts toward fill even though it is not current-carrying for derating.
Verified against NEC 2023 · Table 310.16, Table 250.122, 240.6(A), Chapter 9
A feeder over any real distance also needs a voltage-drop check — run that separately. And this schedule assumes a subpanel in a separate structure is not involved; those bring 250.32 grounding-electrode requirements this tool does not model.
Next steps
How this works
Sizing a dwelling service means adding up the connected load and applying the demand factors the NEC allows for a house, since not everything runs at once. This calculator uses the optional method under NEC 220.82, floor area, appliance nameplates, and heating or cooling load in, minimum service size out, with the math shown line by line instead of just a final number.
The 2026 NEC changes the answer on the same house. Article 220 was renumbered to Article 120, general lighting load dropped from 3 VA per square foot to 2, and the first demand tier dropped from 10 kVA to 8 kVA. On a heavy all-electric house that's enough to drop a 225 amp service to 200, so this tool runs both editions side by side rather than picking one.
Heating and cooling don't add together. NEC 220.82(C) gives six ways to count them and tells you to use whichever is largest, because a heat pump and central air don't run at the same time. And the optional method itself only applies to a single dwelling on one 120/240 or 208Y/120 service of 100 amps or more, NEC 220.82(A); an existing dwelling adding load without a full service recalculation uses 220.83 instead.
Worked example
A 3,500 sq ft all-electric house: range, dryer, water heater, EV charger, pool equipment, hot tub, and a 12,000 VA A/C system.
The 2026 code's lighting and demand changes drop this house from a 225A service to a 200A one: the same house, one code cycle apart.
Frequently Asked Questions
What changed for dwelling load calculations in the 2026 NEC?↓
Three things, and they compound. Article 220 was reorganised into Article 120, so 220.82 is now 120.82. The general lighting and general-use receptacle unit load dropped from 3 VA per square foot to 2 — a change supported by Lawrence Berkeley National Laboratory data putting actual dwelling consumption near 2.3 W per square foot, plus DOE-driven LED adoption. And the optional method's first tier, the part taken at 100 percent, dropped from 10 kVA to 8 kVA. A 3,500 square foot all-electric house that calculates 203 A under the 2023 code calculates 193 A under 2026 — a 200 A service instead of a 225 A one. Check which edition your jurisdiction has actually adopted before you quote.
Why does this calculator only offer the optional method?↓
Because we could not verify Table 220.55 to the standard we hold every rule to here, which is two independent published sources agreeing. The standard method demand-factors household cooking appliances through that table, and no ungated source reproduces the full matrix — one reproduction we found even prints it in the wrong shape, giving a percentage per range where the code gives a kilowatt value. The optional method needs no such table: 220.82(B)(3) takes appliance nameplate ratings directly. It is also the method most residential service and panel-upgrade work actually uses, and it usually yields a smaller service.
Do I add the heating load and the air conditioning load together?↓
No — and this is the most common error in a dwelling calculation. NEC 220.82(C) gives six selections and instructs you to use the largest, because heating and cooling are noncoincident: they do not run at the same time. The six are 100 percent of the air conditioning, 100 percent of a heat pump used without supplemental heat, 100 percent of a heat pump compressor plus 65 percent of its supplemental heat, 65 percent of electric space heating with fewer than four separately controlled units, 40 percent with four or more, and 100 percent of electric thermal storage or any heating expected to run continuously at nameplate.
Can I use the optional method on any house?↓
Not quite. NEC 220.82(A) limits it to a dwelling unit served by a single 120/240-volt or 208Y/120-volt set of 3-wire service or feeder conductors with an ampacity of 100 amperes or greater. That threshold lines up with 230.79(C), which sets 100 amperes as the minimum service for a one-family dwelling anyway. For an existing dwelling where you are adding load rather than sizing a new service, 220.83 is the section that applies instead.
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