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Dwelling unit load calculator

Enter the house: square footage, appliances, range, dryer, heat or A/C, and any EV charger. You get the calculated load in VA and the minimum service size at 240 V.

Built on the 2026 NEC · Free, no sign-up · Updated October 2026

120.41 sets a minimum unit load for lighting and general-use receptacles.

120.52(A). Minimum 2.

120.52(B). Minimum 1.

VA for each one, for example dishwasher, disposal, or water heater. Leave out range, dryer, heat, A/C, and EVSE. 120.53 adds a demand factor for 4 or more.

120.54. Enter the nameplate rating.

Table 120.55 Column C, with Note 1 for ranges over 12 kW. Maximum 27 kW.

120.6. The larger of A/C or heat is included. The smaller is left out.

Optional. 120.57. Enter the nameplate rating. No demand factor.

The result updates as you type.

Result

30065 VA total · service ≥ 126 A at 240 V

How it was calculated

  1. Unit load: 4400 VA, SA: 3000 VA, Laundry: 1500 VA → 8900 VA combined.
  2. Table 120.45 demand factor → 5065 VA general after DF.
  3. Fastened-in-place appliances: 6700 VA × 1.0 = 6700 VA.
  4. Dryer: 5500 VA. Range: 8000 VA.
  5. A/C vs heat (larger of 4800 / 0): 4800 VA.
  6. EVSE: 0 VA.
  7. Total = 30065 VA → 125.27 A at 240 V.

Assumptions

  • 2200 ft² × 2 VA/ft² = 4400 VA minimum unit load per 120.41. This covers lighting and general-use receptacle outlets.
  • Small-appliance: 2 × 1500 VA (120.52(A)). Laundry: 1 × 1500 VA (120.52(B)).
  • Unit load + small-appliance + laundry combined and run through the Table 120.45 dwelling demand factors: 100%/35%/25% bands.
  • Fastened-in-place appliances (3 present) at 100% (120.53 only reduces with 4+).
  • Dryer: larger of nameplate or 5000 VA per 120.54 (Table 120.54 is 100% for one or two dryers).
  • Range: 1 × 12 kW → Table 120.55 Column C 8 kW.
  • A/C vs heat: the larger of the two is used as noncoincident loads per 120.6. Heat is at 100% per 120.51.
  • EVSE: nameplate rating at 100% per 120.57 (7200 VA where no nameplate is available).
  • Output is the standard method (Article 120 Part III). The optional method (120.82) may give a smaller value; this tool does not run the optional method.

Sections used

120.40120.41Table 120.45Table 120.55

These are the sections the calculator applies. Look them up in your code book before you rely on the result, and check the code your AHJ has adopted.

Load calculations moved to Article 120 in 2026

The 2026 NEC moved the branch-circuit, feeder, and service load calculations out of Article 220 and into a new Article 120 in Chapter 1. The method is the same idea, but the section numbers are different, and some values changed.

The one that matters most on a house: the minimum unit load for dwellings in 120.41 is 2 volt-amperes per square foot. Older editions used 3 VA/ft². If you learned load calcs on the 2023 code, check your numbers against the edition your AHJ enforces.

The standard method, step by step

  • General load: floor area × 2 VA/ft² (120.41), plus 1,500 VA for each small-appliance circuit and each laundry circuit (120.52).
  • Apply the demand factors in Table 120.45 to that total: the first 3,000 VA at 100%, the next 117,000 VA at 35%, and the rest at 25%.
  • Fastened-in-place appliances such as a dishwasher, disposal, and water heater: 100%, or 75% if there are four or more (120.53).
  • Dryer: nameplate rating or 5,000 VA, whichever is larger (120.54).
  • Range: Table 120.55, Column C for one range up to 12 kW is 8 kW, increased 5% for each kW over 12.
  • Heat or A/C: include the larger of the two and leave out the smaller (120.6, noncoincident loads).
  • EV charger: the nameplate rating at 100%, with no demand factor (120.57).
  • Add them up and divide by 240 V for the minimum service amps.

What this calculator doesn't cover

This is the standard method for one dwelling unit. The optional method for dwellings, multifamily demand factors, and load management systems for EV chargers have their own rules. The calculator shows the minimum calculated load, which is not always the service size you should install.

2023 to 2026: our list has 15 changes in Article 120, which was Article 220 in 2023. See the changes

Worked example

A 2,200 ft² house with a dishwasher, disposal, and water heater, a 5.5 kW dryer, a 12 kW range, and 4.8 kVA of A/C:

  • Floor area (sq ft): 2200
  • Small-appliance circuits (20 A): 2
  • Laundry circuits (20 A): 1
  • Fastened-in-place appliances (VA): 1200, 1000, 4500
  • Dryer (VA): 5500
  • Range or cooking (kW): 12
  • Range count: 1
  • A/C connected load (VA): 4800
  • Electric heat (VA): 0

Result

30065 VA total · service ≥ 126 A at 240 V

How it was calculated

  1. Unit load: 4400 VA, SA: 3000 VA, Laundry: 1500 VA → 8900 VA combined.
  2. Table 120.45 demand factor → 5065 VA general after DF.
  3. Fastened-in-place appliances: 6700 VA × 1.0 = 6700 VA.
  4. Dryer: 5500 VA. Range: 8000 VA.
  5. A/C vs heat (larger of 4800 / 0): 4800 VA.
  6. EVSE: 0 VA.
  7. Total = 30065 VA → 125.27 A at 240 V.

Assumptions

  • 2200 ft² × 2 VA/ft² = 4400 VA minimum unit load per 120.41. This covers lighting and general-use receptacle outlets.
  • Small-appliance: 2 × 1500 VA (120.52(A)). Laundry: 1 × 1500 VA (120.52(B)).
  • Unit load + small-appliance + laundry combined and run through the Table 120.45 dwelling demand factors: 100%/35%/25% bands.
  • Fastened-in-place appliances (3 present) at 100% (120.53 only reduces with 4+).
  • Dryer: larger of nameplate or 5000 VA per 120.54 (Table 120.54 is 100% for one or two dryers).
  • Range: 1 × 12 kW → Table 120.55 Column C 8 kW.
  • A/C vs heat: the larger of the two is used as noncoincident loads per 120.6. Heat is at 100% per 120.51.
  • EVSE: nameplate rating at 100% per 120.57 (7200 VA where no nameplate is available).
  • Output is the standard method (Article 120 Part III). The optional method (120.82) may give a smaller value; this tool does not run the optional method.

Sections used

120.40120.41Table 120.45Table 120.55

These are the sections the calculator applies. Look them up in your code book before you rely on the result, and check the code your AHJ has adopted.

Questions electricians ask

How do I do a dwelling unit load calculation?

Work down the standard method in order: general lighting at 2 VA per square foot (120.41) plus 1,500 VA for each small-appliance and laundry circuit (120.52), then the Table 120.45 demand factors, then the fastened-in-place appliances, dryer, range, the larger of heat or A/C, and any EV charger. Add the results and divide by 240 V for the minimum service amps. The steps above list each one with its section, and the calculator does the arithmetic.

Is there a worked example of a service load calculation?

Yes. The example below the calculator runs a 2,200 ft² house through every step and ends with the minimum service amps. Enter the same numbers to check your own worksheet line by line.

What is the formula for the general lighting load in a house?

Floor area in square feet times 2 VA (120.41), plus 1,500 VA for each small-appliance circuit and each laundry circuit (120.52). Apply the Table 120.45 demand factors to that total before you add the other loads.

What changed in the 2026 NEC for residential load calculations?

The calculations moved from Article 220 to Article 120, and the dwelling minimum unit load in 120.41 is 2 VA per square foot. Check which edition your jurisdiction has adopted before you rely on either number.

How do I add an EV charger to a load calculation?

Enter the charger's nameplate VA. Under 120.57 it goes in at its nameplate rating with no demand factor. A load management system can reduce the load you have to count; the calculator doesn't model that.

Do I count both heat and air conditioning?

No. They don't run at the same time, so only the larger of the two goes in the calculation (120.6).

Will a 100 A service handle my house?

Run your numbers. If the calculated load divided by 240 V comes out under 100 A, a 100 A service meets the minimum. Many electricians still leave room for future loads.

Practice it hands-on

Drag floor area, circuits, and appliances onto a load calculation, and then size the service.

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Teach it in one class

Free slides, quiz, and instructor note: Dwelling load calculation (NEC 2026 Article 120).

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How this calculator was built

The calculator runs the same code as the Ask Shorty iPhone app. Automated tests check it against hand-worked answers, and every section it names is checked against the 2026 NEC text. It shows section numbers, not code text. Read the sections in your own code book and confirm which edition your AHJ enforces.

How we test the calculators. See something wrong? Tell us and we will check it against the code.

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