If there is one skill that separates someone who has memorized a few NEC section numbers from someone who actually understands electrical design, it's the load calculation. Article 220 shows up constantly on journeyman and master exams because it is the backbone of how you decide what size service, feeder, and panel a building actually needs. Get it wrong on a real job and you either undersize a service (a genuine safety and code violation) or oversize it (an expensive, unnecessary mistake). Get it wrong on the exam and you'll miss several questions that all hinge on the same underlying math. This article walks through the standard method calculation from the ground up, works through three complete dwelling examples of different sizes, covers the optional method, and finishes with a simplified commercial/multifamily example — all with every arithmetic step shown so you can follow along with a calculator in hand.
What a Load Calculation Actually Does
At its core, a load calculation answers one question: "If every circuit in this building were used at once, how much current would actually flow through the service conductors?" The honest answer is that they never all run at once — nobody runs every light, every outlet, the range, the dryer, the water heater, and every HVAC unit simultaneously at full draw. Article 220 recognizes this reality and builds in demand factors — percentage reductions applied to certain load categories — so the calculated total reflects realistic, coincident usage rather than a worst-case fantasy that would force every service in the country to be needlessly oversized.
At the same time, load calculations are deliberately conservative in other places. Some categories get no demand factor reduction at all, and safety margins are built in through rounding rules and minimum circuit requirements. The result is a number that is realistic, but still safe. Understanding why each step exists — not just memorizing the sequence — is what will get you through both the exam and a real design problem.
Two Ways to Calculate a Dwelling Load
NEC Article 220 gives you two legitimate paths for a dwelling unit:
- The standard method — builds the total load piece by piece: general lighting, small appliance and laundry circuits, fixed appliances, HVAC, and the largest motor, then applies demand factors to specific categories along the way.
- The optional method — a simplified, more heavily demand-factored approach available for dwellings that meet certain conditions (a single dwelling unit served by one 100-amp-or-larger service, for example). It lumps most loads together and applies one broad demand-factor curve to the whole thing.
We'll walk the standard method in full detail first since it teaches you the underlying logic, then come back and compare it to the optional method later in this article.
Step 1: General Lighting and Receptacle Load
Every dwelling calculation starts with a general lighting load, expressed as a certain number of volt-amps (VA) per square foot of the building's floor area. This single figure is meant to represent all the general-purpose lighting and receptacle outlets throughout the home — not just fixtures, but ordinary wall receptacles too, since either could have a lamp or a light-duty load plugged into it.
For most of the life of the modern NEC, that figure has been 3 VA per square foot for dwelling units. (As covered later in the "How This Changed" section, the 2026 edition lowers this figure — always check which edition your jurisdiction has adopted before doing a real-world calculation.) The floor area used is the outside dimensions of the dwelling, not counting open porches, garages, or unfinished spaces that won't be used for living purposes — but it does include every finished, habitable floor level, including finished basements and upper floors.
Quick illustration — general lighting load for a 1,500 sq ft home
General lighting VA = Area (sq ft) × 3 VA/sq ft
General lighting VA = 1,500 × 3
General lighting VA = 4,500 VA
Step 2: Small Appliance and Laundry Circuits
On top of general lighting, a dwelling calculation adds a fixed VA allowance for the small-appliance circuits that serve kitchen countertop receptacles, and a separate allowance for the laundry circuit. These are counted separately from general lighting because the code requires them to be on their own dedicated 20-amp circuits in the first place — they're not just "some more lighting," they're specific, required circuits that see genuine concentrated loads (toasters, coffee makers, irons, and so on).
A commonly used, trade-standard figure is 1,500 VA for each required small-appliance circuit (a dwelling needs at least two of these) and 1,500 VA for the laundry circuit. These figures have been stable across many code cycles, but you should always confirm the exact current value in your adopted edition before relying on it for real design work — this article treats them as widely used planning values, not as a substitute for reading your code book's current table.
Continuing the 1,500 sq ft example — adding small appliance and laundry circuits
Two small-appliance circuits: 2 × 1,500 VA = 3,000 VA
One laundry circuit: 1 × 1,500 VA = 1,500 VA
Combined with general lighting: 4,500 + 3,000 + 1,500
Combined "general lighting + small appliance + laundry" VA = 9,000 VA
Step 3: Applying the Demand Factor to That Combined Total
Here's where the calculation stops being pure addition and starts reflecting real-world usage. Nobody uses every light, every countertop appliance, and the washing machine at full draw simultaneously — so the code allows this combined "general lighting + small appliance + laundry" total to be reduced using a demand factor table. The concept, going back many decades of code history, works like a tiered curve: the first several thousand volt-amps are counted at 100% (because a home is going to use at least that much lighting and receptacle load fairly routinely), and the remainder above that threshold is counted at a reduced percentage, because it becomes statistically less likely that every additional increment is actually in use at the same moment.
The exact break points and percentages are published in the demand factor table your adopted NEC edition uses (renumbered to Table 220.42(B) in the 2023 edition — see the "How This Changed" section below). For the worked examples in this article, we'll use commonly cited illustrative demand-factor break points — 100% of the first 3,000 VA, and 35% of everything above that — clearly labeled as example values. Always verify the actual current table in your code book before using these numbers on a real job or a state exam that expects an exact table lookup.
Applying an illustrative demand factor to our 1,500 sq ft example
Combined total: 9,000 VA
First 3,000 VA @ 100% = 3,000 VA
Remaining (9,000 − 3,000) = 6,000 VA @ 35% = 2,100 VA
Total after demand factor: 3,000 + 2,100
Demand-adjusted general lighting/small appliance/laundry load = 5,100 VA
Notice what just happened: the raw 9,000 VA dropped to 5,100 VA once the demand factor was applied. That's the entire philosophy of Article 220 in miniature — start with a realistic per-unit allowance, add up everything required, then apply a demand curve where the code recognizes that not everything runs at once.
Step 4: Fixed Appliances and the "Four or More" Rule
Next come fixed appliances — things like a dishwasher, garbage disposal, water heater, or built-in microwave that are permanently connected rather than plugged into a general-purpose receptacle. Each fixed appliance's nameplate VA (or watts, which for this purpose is treated the same as VA for resistive/simple loads) gets added to the running total.
Here's a detail that trips people up on exams: if a dwelling has four or more fixed appliances (not counting ranges, dryers, space heating, or air conditioning, which are handled separately), the code allows those fixed appliance loads to be totaled together and then reduced by a demand factor — commonly cited around 75% — before being added into the overall calculation. If there are fewer than four fixed appliances, no such demand factor applies and you add them at 100% of nameplate.
Example — a home with four fixed appliances
Dishwasher: 1,200 VA
Disposal: 900 VA
Built-in microwave: 1,500 VA
Water heater: 4,500 VA
Raw total: 1,200 + 900 + 1,500 + 4,500 = 8,100 VA
Because there are 4 fixed appliances, apply an illustrative 75% demand factor:
8,100 × 0.75
Demand-adjusted fixed appliance load = 6,075 VA
Step 5: Dryers and Ranges
Clothes dryers and electric ranges get their own dedicated demand tables in the NEC, separate from the general fixed-appliance rule, because they're extremely common in dwellings and have very predictable usage patterns that the code committee has studied over many decades.
Dryers: The conceptual approach is that a single dwelling-unit dryer is counted using either a set minimum value or its actual nameplate rating (whichever is larger), and when multiple dwelling units share a calculation (like a duplex or small multifamily building), a demand factor curve reduces the total as the number of dryers increases — because it becomes less likely that every unit's dryer runs at the exact same moment. For a single dwelling unit, no demand reduction typically applies to that one dryer — you use the full assumed or nameplate value.
Ranges: Electric ranges use their own demand table that already has demand factors baked in for typical dwelling nameplate ratings, because a range's actual full-nameplate draw (all burners and the oven at once) essentially never happens in practice — people don't run every burner and self-clean the oven simultaneously. For a single range in the roughly 8–12 kW nameplate class common in residential kitchens, a commonly cited assumed demand value used for illustration in this article is 8,000 VA. This is presented as an illustrative planning number only — always look up the actual figure for the specific nameplate rating in your current code book's range demand table.
Example — adding a dryer and range to a calculation
Dryer, single dwelling unit, assumed nameplate: 5,000 VA (no demand reduction for a single unit)
Range, single dwelling unit, illustrative demand value: 8,000 VA
Combined dryer + range load: 5,000 + 8,000
Dryer + range subtotal = 13,000 VA
Step 6: HVAC — Use the Larger of Heating or Cooling
Heating and air conditioning are almost never both running at full draw at the same instant in a typical single-zone residential system — it's either heating season or cooling season. Because of that, the standard method has you calculate both the heating load and the air-conditioning load, and then include only the larger of the two in the final total, rather than adding both.
Example — choosing between heating and cooling
Air conditioning condenser + air handler: 4,200 VA
Electric furnace heat strips: 9,600 VA
Since heating (9,600 VA) is larger than cooling (4,200 VA), include only the heating load.
HVAC load included in calculation = 9,600 VA
Step 7: The Largest Motor Rule
If the dwelling has one or more motor loads (a well pump, a large exhaust fan, a hot tub motor, etc.), the code requires you to take the single largest motor on the property and add an extra 25% of that motor's load on top of everything else already calculated. The logic here is about motor starting current — when a motor starts, it briefly draws significantly more current than its running rating, and the system needs headroom for that inrush without nuisance tripping the main disconnect. Only the single largest motor gets this 25% adder; every other, smaller motor is simply counted at its normal running value elsewhere in the calculation.
Example — largest motor adder
Well pump motor (largest motor on the property): 1,200 VA
25% adder: 1,200 × 0.25 = 300 VA
Amount added to the total for the largest-motor rule = 300 VA
Worked Example 1: Small Home — 1,200 Square Feet, Standard Method
Let's put every step together on a modest 1,200 sq ft single-story home with a gas furnace (so only cooling counts toward the electrical HVAC load), an electric water heater, a dishwasher, and a standard electric range with no separate dryer circuit demand issue (single dryer, no multi-unit demand reduction).
1,200 sq ft home — full standard method walkthrough
General lighting: 1,200 sq ft × 3 VA/sq ft = 3,600 VA
Small appliance circuits: 2 × 1,500 VA = 3,000 VA
Laundry circuit: 1,500 VA
Combined lighting/appliance/laundry subtotal: 3,600 + 3,000 + 1,500 = 8,100 VA
Apply illustrative demand factor (100% first 3,000 VA, 35% remainder):
First 3,000 VA @ 100% = 3,000 VA
Remaining 5,100 VA @ 35% = 1,785 VA
Demand-adjusted subtotal = 3,000 + 1,785 = 4,785 VA
Fixed appliances (only two: dishwasher 1,200 VA + water heater 4,500 VA = 5,700 VA — fewer than 4, so no demand factor, full value counted):
Fixed appliance total = 5,700 VA
Range (illustrative demand value): 8,000 VA
Air conditioning (only cooling counts — gas heat has no electrical load here): 3,600 VA
Grand total:
4,785 (lighting/appliance/laundry) + 5,700 (fixed appliances) + 8,000 (range) + 3,600 (AC)
= 4,785 + 5,700 + 8,000 + 3,600
Total connected load = 22,085 VA
From Total VA to Service Amps
Once you have a final total VA figure, converting it to a required service ampacity is straightforward Ohm's Law-style arithmetic. For a standard single-phase 120/240V dwelling service, divide total VA by 240 volts to get amps.
Converting the 1,200 sq ft home's total to service amps
Amps = VA ÷ Voltage
Amps = 22,085 ÷ 240
Amps = 92.02 amps
Since services are only available in standard sizes, round up to the next standard size.
Minimum service size = 100 amps
Standard residential service sizes commonly used in the trade include 100A, 125A, 150A, 200A, 320A (for services with meter-panel combinations), and 400A. You always round up to the next standard size available from the equipment you're using — you never round down, and you never install a "custom" in-between size.
Worked Example 2: Mid-Size Home — 2,400 Square Feet, Standard Method
Now let's scale up to a 2,400 sq ft two-story home with central electric heat pump heating/cooling, an electric range, an electric dryer, a dishwasher, a garbage disposal, a built-in microwave, and an electric water heater — giving us four fixed appliances, which means the fixed-appliance demand factor now applies.
2,400 sq ft home — full standard method walkthrough
General lighting: 2,400 × 3 = 7,200 VA
Small appliance circuits: 2 × 1,500 = 3,000 VA
Laundry circuit: 1,500 VA
Combined subtotal: 7,200 + 3,000 + 1,500 = 11,700 VA
Demand factor: first 3,000 VA @ 100% = 3,000 VA; remaining 8,700 VA @ 35% = 3,045 VA
Demand-adjusted subtotal = 3,000 + 3,045 = 6,045 VA
Fixed appliances (four, so demand factor applies):
Dishwasher 1,200 + Disposal 900 + Microwave 1,500 + Water heater 4,500 = 8,100 VA
Illustrative 75% demand factor: 8,100 × 0.75 = 6,075 VA
Range (illustrative demand value, larger family-size unit): 8,800 VA
Dryer (single dwelling unit, no demand reduction): 5,000 VA
Heat pump heating vs. cooling — compare and use the larger:
Cooling mode draw: 5,400 VA
Heating mode draw (with backup strip heat): 10,200 VA
Use the larger: 10,200 VA
Grand total:
6,045 + 6,075 + 8,800 + 5,000 + 10,200
Total connected load = 36,120 VA
Converting the 2,400 sq ft home's total to service amps
Amps = 36,120 ÷ 240 = 150.5 amps
Round up to the next standard size.
Minimum service size = 200 amps (since 150.5A exceeds a 150A service's practical margin, most designers jump to the next common standard, 200A, especially once you factor in that a 150A rated service leaves almost no headroom)
Worked Example 3: Larger Home — 3,600 Square Feet, Multiple Large Appliances, EV Charger, and a Well Pump
Now a larger, more heavily loaded home: 3,600 sq ft, electric range, electric dryer, dishwasher, disposal, built-in microwave, water heater, central air conditioning with a gas furnace (so only cooling counts electrically), a 40-amp Level 2 EV charger, and a well pump motor.
3,600 sq ft home — full standard method walkthrough
General lighting: 3,600 × 3 = 10,800 VA
Small appliance circuits: 2 × 1,500 = 3,000 VA
Laundry circuit: 1,500 VA
Combined subtotal: 10,800 + 3,000 + 1,500 = 15,300 VA
Demand factor: first 3,000 VA @ 100% = 3,000 VA; remaining 12,300 VA @ 35% = 4,305 VA
Demand-adjusted subtotal = 3,000 + 4,305 = 7,305 VA
Fixed appliances (four, demand factor applies):
Dishwasher 1,300 + Disposal 900 + Microwave 1,600 + Water heater 4,500 = 8,300 VA
Illustrative 75% demand factor: 8,300 × 0.75 = 6,225 VA
Range (illustrative demand value): 8,800 VA
Dryer (single unit, no demand reduction): 5,500 VA
Air conditioning (gas heat, so cooling is the only HVAC electrical load): 6,000 VA
EV charger (240V, 40A, continuous-duty load counted at nameplate for this illustration): 9,600 VA
Largest motor rule — well pump, largest motor at 1,500 VA:
25% adder = 1,500 × 0.25 = 375 VA
Grand total:
7,305 + 6,225 + 8,800 + 5,500 + 6,000 + 9,600 + 375
Total connected load = 43,805 VA
Converting the 3,600 sq ft home's total to service amps
Amps = 43,805 ÷ 240 = 182.5 amps
Round up to the next standard size.
Minimum service size = 200 amps
The Optional Method for Dwellings
The standard method above is thorough, but it's also a lot of bookkeeping for a single-family home. The NEC also allows an optional method for dwelling units that meet certain conditions — most commonly, a single dwelling unit supplied by a service or feeder rated 100 amps or more, with no more than one set of feeder conductors.
Conceptually, the optional method works very differently from the standard method:
- Instead of separating general lighting, small appliances, laundry, and fixed appliances into their own demand-factor calculations, the optional method lumps nearly everything together — general lighting, small appliance/laundry allowances, and all fixed appliances (including range and dryer) — into one big combined total.
- It then applies one broad, more aggressive demand curve to that combined total: the first several thousand VA at 100%, and everything above that at a lower flat percentage (commonly cited around 40% in the trade for the amount above the threshold, though you must confirm the current figure in your code book).
- Air conditioning and heating are still compared and only the larger value included, added on top of the demand-reduced general total — this part of the logic carries over from the standard method.
The appeal of the optional method is speed: fewer separate demand-factor lookups, fewer opportunities to make an arithmetic mistake, and in many typical dwelling situations it produces a similar or even a somewhat lower total than painstakingly working the standard method line by line. The tradeoff is that it's less transparent — it doesn't show you exactly where every VA came from — and it's only available when the dwelling meets the eligibility conditions (a single dwelling unit, adequately rated service, etc.). A duplex, a mixed-use building, or a dwelling with unusual load characteristics may not qualify, and in those cases you're back to the standard method.
Worked Example 4: Optional Method on the 2,400 Square Foot Home
Let's re-run Worked Example 2's 2,400 sq ft home using the optional method, so you can see how the two approaches compare on the exact same house.
2,400 sq ft home — optional method walkthrough
Combine everything except HVAC into one total:
General lighting: 2,400 × 3 = 7,200 VA
Small appliance circuits: 3,000 VA
Laundry: 1,500 VA
Water heater: 4,500 VA
Dishwasher: 1,200 VA
Disposal: 900 VA
Microwave: 1,500 VA
Range (full nameplate-style value used under the optional method, illustrative): 12,000 VA
Dryer (full nameplate-style value used under the optional method, illustrative): 5,500 VA
Combined raw total: 7,200 + 3,000 + 1,500 + 4,500 + 1,200 + 900 + 1,500 + 12,000 + 5,500 = 37,300 VA
Apply an illustrative optional-method demand curve — first 10,000 VA @ 100%, remainder @ 40%:
First 10,000 VA @ 100% = 10,000 VA
Remaining 27,300 VA @ 40% = 10,920 VA
Demand-adjusted general total = 10,000 + 10,920 = 20,920 VA
HVAC — larger of heating/cooling (same as Example 2): 10,200 VA
Grand total: 20,920 + 10,200
Total connected load (optional method) = 31,120 VA
Compare that to the standard-method total for the same house in Worked Example 2 (36,120 VA). Both are legitimate, code-compliant results — they simply come from two different, both-valid demand-factor philosophies. This is exactly why the exam likes to test whether you know which method is being asked for in a given question, because the two methods can produce genuinely different final numbers on the same building.
Converting the optional-method total to service amps
Amps = 31,120 ÷ 240 = 129.7 amps
Round up to the next standard size.
Minimum service size = 150 amps (versus 200 amps under the standard method for the same house)
Worked Example 5: Simplified Commercial/Multifamily Load Calculation
Commercial and multifamily load calculations follow the same underlying logic — a per-square-foot general lighting/receptacle allowance, plus specific equipment loads, plus demand factors where the code allows them — but the VA/sq ft figures and applicable demand tables differ by occupancy type (office, retail, warehouse, school, etc.), and many equipment loads (rooftop units, elevators, kitchen equipment) are counted individually rather than through a residential-style appliance table.
Let's walk a simplified example: an 8,000 sq ft small retail/office building with a rooftop HVAC package unit and general lighting/receptacle loads only (no cooking equipment, no elevator, for simplicity).
8,000 sq ft simplified commercial building — walkthrough
General lighting/receptacle load (illustrative commercial VA/sq ft value — commercial occupancy classes use their own published figures, always confirm the correct value for the specific occupancy type in your code book; using 3.5 VA/sq ft for this illustration):
8,000 × 3.5 = 28,000 VA
Rooftop HVAC package unit (nameplate): 18,000 VA
Demand factor on general lighting — commercial general lighting loads are commonly subject to their own demand curve once the total climbs high enough; for this illustration assume the first 20,000 VA is counted at 100% and the remainder at 50%:
First 20,000 VA @ 100% = 20,000 VA
Remaining 8,000 VA @ 50% = 4,000 VA
Demand-adjusted lighting total = 20,000 + 4,000 = 24,000 VA
Grand total: 24,000 (lighting) + 18,000 (rooftop unit)
Total connected load = 42,000 VA
Converting the commercial building's total to service amps (three-phase, 208V)
For a three-phase system, Amps = VA ÷ (Voltage × 1.732)
Amps = 42,000 ÷ (208 × 1.732)
Amps = 42,000 ÷ 360.3
Amps = 116.6 amps
Round up to the next standard size.
Minimum service size = 125 amps
Multifamily buildings (apartment complexes, for example) add another layer: each dwelling unit gets its own individual load calculated (often using the optional method per-unit), and then those individual unit totals are combined with house loads (hallway lighting, shared laundry rooms, elevators, exterior lighting) using their own demand factors for multi-unit buildings — because it becomes statistically very unlikely that every single unit in a 40-unit building hits its own individual peak load at the exact same instant. The more units in the building, the more aggressive the applicable demand factor typically becomes, which is why large apartment services are sized nowhere near "40 times a single unit's peak load."
Quick-Reference: How the Standard Method Builds Up
| Load Category | How It's Counted | Demand Factor Applied? |
|---|---|---|
| General lighting | VA/sq ft × floor area | Yes — combined with small appliance/laundry, tiered curve |
| Small appliance circuits | Fixed VA per required circuit (2 minimum) | Yes — combined with lighting above |
| Laundry circuit | Fixed VA per required circuit | Yes — combined with lighting above |
| Fixed appliances (fewer than 4) | Full nameplate VA, added directly | No |
| Fixed appliances (4 or more) | Full nameplate VA, summed, then reduced | Yes — illustrative 75% |
| Electric range | Table-based demand value by nameplate class | Built into the table itself |
| Electric dryer | Nameplate or minimum value; multi-unit demand only for multiple dwelling units | Only for multiple units on one calculation |
| Heating vs. cooling | Calculate both, use the larger only | N/A — larger-of rule instead |
| Largest motor | Add 25% of the single largest motor's load | N/A — adder rule instead |
Common Mistakes
How This Changed: NEC 2020 → 2023 → 2026
Load calculation content in Article 220 has been renumbered and adjusted across recent code cycles, and it's worth knowing the shape of those changes even if you don't have every subsection memorized.
Between the 2020 and 2023 editions, the general lighting load table that most electricians know as "Table 220.12" was renumbered to Table 220.42(A), and the associated demand factor table moved to Table 220.42(B). The underlying method and logic stayed conceptually the same — this was primarily a reorganization of Article 220's internal structure, not a wholesale rewrite of how you calculate a dwelling load. If you're studying from an older textbook or an online resource that still references "220.12," recognize that as the pre-2023 numbering for the same general lighting load table.
The 2026 edition brings a more substantial change: load calculation content moves out of Article 220 entirely and into a renumbered Article 120, though the underlying calculation method carries over conceptually. More importantly for the actual math, the 2026 edition drops the dwelling unit general lighting load figure from 3 VA per square foot down to 2 VA per square foot — a genuine, substantive reduction that reflects modern LED lighting's dramatically lower power draw compared to the incandescent-era assumptions baked into the original 3 VA/sq ft figure. If your jurisdiction has adopted the 2026 NEC, every general lighting calculation in this article using 3 VA/sq ft would instead use 2 VA/sq ft, which meaningfully lowers the general lighting portion of the total.
Beyond these two documented changes, other aspects of Article 220 (specific demand factor percentages, table break points, appliance-specific tables) have seen incremental adjustments across code cycles as well. Always confirm the exact current figures against the specific NEC edition your jurisdiction has legally adopted — code adoption lags the publication cycle in most states, so "the newest edition" and "the edition that's actually enforced where you're working" are frequently not the same document.
Frequently Asked Questions
Do I have to use the standard method, or can I always use the optional method?
The optional method is only available when a dwelling meets specific eligibility conditions — most commonly, a single dwelling unit served by a single feeder or service rated at least 100 amps. A duplex, a mixed occupancy, or a service that doesn't meet the minimum rating typically has to use the standard method. Always confirm eligibility before choosing the optional method on an exam question or a real design.
Why does the exam ask about both methods if they give different answers on the same house?
Because both are legitimate, code-compliant tools, and a licensed electrician needs to recognize which one a given scenario calls for. The standard method is more granular and transparent; the optional method is faster but less detailed. Exam questions will typically tell you explicitly which method to use — read the question stem carefully.
Does general lighting load include actual light fixtures only, or also regular wall receptacles?
It includes both. The general lighting VA/sq ft figure is meant to represent the combined general-purpose lighting and receptacle load throughout the dwelling, not just fixtures. That's part of why it's expressed as a blanket per-square-foot allowance rather than a fixture-by-fixture count.
What happens if a house has no laundry circuit — do I still add the 1,500 VA for it?
If the dwelling genuinely has no laundry circuit (a rare situation, since most jurisdictions and modern homes do provide one), you would not add a load that doesn't exist. In practice, nearly every calculation you'll see on an exam or in the field includes a laundry circuit allowance because nearly every dwelling has one.
Why does the largest motor get a 25% adder but not every motor?
The 25% adder exists to cover motor starting (inrush) current headroom. Only the single largest motor is likely to matter for that purpose in a worst-case simultaneous-start scenario combined with everything else already running, so the code only requires the adder on that one largest motor rather than stacking it on every motor in the building.
Is an EV charger treated as a "fixed appliance" for the four-or-more demand factor?
Treatment of EV charging equipment in a load calculation is a nuanced, evolving area, and different designers and jurisdictions may treat it somewhat differently — as a continuous load requiring 125% conductor sizing, and/or as a load counted in the general fixed-appliance bucket, depending on specifics. Always check current code guidance and any load management provisions (like an energy management system limiting simultaneous draw) rather than assuming a blanket treatment.
Do commercial buildings use the same 3 VA/sq ft figure as dwellings?
No. Commercial and other non-dwelling occupancies use their own published general lighting VA/sq ft figures that vary by occupancy classification (office, retail, warehouse, school, hospital, etc.) — these are different values from the dwelling unit figure, and you must look up the correct occupancy classification's figure rather than reusing residential numbers.
Why did the 2026 edition lower the general lighting figure to 2 VA/sq ft?
The change reflects the shift to far more efficient LED lighting technology across the housing stock, which draws meaningfully less power per fixture than the incandescent and early fluorescent technology that the original figure was built around decades ago. It's a recognition that real-world lighting loads have genuinely dropped, not just a numbering cleanup.
Key Terms
- Volt-Amp (VA): The unit load calculations are expressed in — for most simple resistive loads, numerically equal to watts, and used because it accounts for both current and voltage relationships in a circuit.
- Demand Factor: A percentage reduction applied to a load category to reflect that not all connected loads in that category operate simultaneously at full capacity.
- Standard Method: The detailed, line-item Article 220 dwelling load calculation approach that separates and demand-factors each load category individually.
- Optional Method: A simplified dwelling calculation approach available under specific eligibility conditions, combining most loads into one total before applying a single broad demand curve.
- Connected Load: The full nameplate or rated value of a piece of equipment before any demand factor reduction is applied.
- Service Sizing: The process of converting a final calculated VA total into a required ampacity, then selecting the next standard equipment size that meets or exceeds that value.
Load calculations connect directly to several other topics you'll want to be solid on for the exam. Review branch circuits under NEC 210 to understand how individual circuits feed into the totals used here, and service entrance and disconnects under NEC 230 to see what happens once you know your required service size. If motors specifically are giving you trouble, motor circuits under NEC 430 goes deeper into motor-specific sizing rules. When you're ready to test yourself, try the single-family dwelling unit practice questions and the commercial load calculations practice test, or browse the full NEC code question category for more.
Disclaimer: This article is a study aid to help you understand the logic and structure of NEC Article 220 load calculations. Specific VA figures, demand factor percentages, and table values used in the worked examples are illustrative planning numbers for teaching purposes. Always verify exact current requirements against the official NEC edition adopted in your jurisdiction, and any local amendments, before performing a real-world load calculation or relying on specific numbers for an exam that requires exact table lookups.