Residential Electrical Load Calculator
Dwelling service load by the NEC Article 220 standard (general) method, where each load category carries its own demand factor: Table 220.42 lighting, 220.53 appliances, Table 220.54 dryer, Table 220.55 range, noncoincident heating and air conditioning, and the 25% largest-motor adder. Every line is shown so the calculation checks out for permit paperwork. Reach for the optional-method tool instead when the shorter 220.82 calc applies.
How to use this calculator
- Enter the floor area from outside dimensions, counting habitable and adaptable space (unfinished basements count; open porches and garages do not, per NEC 220.12).
- Total the nameplate VA of fastened-in-place appliances that are not the range, dryer, heat, or A/C (water heater, dishwasher, disposal, compactor), and enter how many there are. Four or more gets the 220.53 75% factor.
- Enter the range count and each unit's kW rating, plus the electric dryer nameplate. The tool applies Table 220.55 Column C and the 5000 VA dryer minimum automatically.
- Enter heating and A/C nameplates (only the larger is counted) and the largest motor. Read the calculated amps and the recommended standard service size; the breakdown shows every category demand for permit paperwork.
NEC reference
This calculator implements the NEC 2020 Article 220, Part III standard calculation for a single dwelling: general lighting at 3 VA/ft² (Table 220.12) plus small-appliance and laundry circuits (220.52), all reduced by the Table 220.42 demand factors; fastened-in-place appliances at 75% for four or more (220.53); the electric dryer at 5000 VA or nameplate (220.54); household cooking per Table 220.55 Column C with Note 1; heating and air conditioning as noncoincident loads (220.60); and 25% of the largest motor (220.50, referencing 430.24). The recommended service is the smallest 240.6(A) rating at or above the calculated amps, floored at the 100 A one-family-dwelling minimum (230.79(C)). It is the standard method, not the optional 220.82 method, and does not cover multifamily (220.84) or existing-dwelling additions (220.83).
Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.
Worked example: 1500 ft² all-electric dwelling
These are the same numbers the calculator produces from its default inputs, so you can verify the tool against the worksheet directly.
| Category | Basis | Demand VA |
|---|---|---|
| Lighting, small-appliance, laundry | 9000 VA connected, Table 220.42: 3000 + 6000 × 0.35 | 5,100 |
| Fixed appliances (4, so 75%) | 7800 VA × 0.75 (220.53) | 5,850 |
| Electric dryer | max(5000, nameplate) (220.54) | 5,000 |
| Range, 12 kW | Table 220.55 Column C, one unit | 8,000 |
| Heat vs A/C | max(9000 heat, 5000 A/C) (220.60) | 9,000 |
| Largest motor, 25% | 5000 VA × 0.25 (220.50) | 1,250 |
| Total | 34,200 |
34,200 VA ÷ 240 V = 142.5 A, so a 150 A minimum standard rating, commonly installed as a 200 A service. Run the same dwelling through the optional method (220.82) and the total usually comes out equal or lower. The standard method is the conservative baseline.
Frequently asked questions
Standard method or optional method?
Both are code-compliant for a single dwelling on a 100 A-or-larger, 120/240 V service. The optional method (220.82) is shorter and usually gives the same or a smaller service, so it dominates residential permits. Use the standard method when the dwelling does not qualify for the optional method, when an inspector wants the category-by-category worksheet, or when you are checking an exam problem, since the standard method is what most study guides teach.
How do the Table 220.42 lighting tiers work?
Add the general lighting load (3 VA/ft²) to every small-appliance and laundry circuit at 1500 VA each, then apply the demand factors: the first 3000 VA at 100%, everything from 3001 to 120,000 VA at 35%, and any remainder at 25%. A 1500 ft² house lands entirely in the first two tiers, so 9000 VA connected becomes 5100 VA of demand.
When does the 75% appliance factor apply?
NEC 220.53 lets you take fastened-in-place appliances at 75% of their combined nameplate only when there are four or more of them, and it excludes the range, dryer, space heating, and A/C, which have their own categories. Three or fewer fixed appliances are taken at 100%. Enter the count so the tool applies the right factor.
What if the range is over 12 kW?
Table 220.55 Note 1 raises the Column C demand by 5% for each kilowatt (or major fraction) above 12. A single 16 kW range is 8 kW × 1.20 = 9.6 kW. Ranges rated 8¾ kW or less may use the lower Columns A/B; this tool always uses Column C, which never undersizes.
Related calculators
- Electrical Load Calculator covers the optional method (220.82) for the same dwelling; usually shorter.
- Breaker Size Calculator sizes the individual branch circuits feeding these loads.
- Wire Size Calculator sizes service and feeder conductors for the calculated load.
- Voltage Drop Calculator handles long service laterals and feeders to outbuildings.
Studying for the licensing exam? Our own NEC Code Quickstart works all twelve exam calculations start to finish, each with the code reference. Also in paperback.
Running an electrical contracting business? Jobber handles scheduling, invoicing, and job management. Start a 14-day free trial.
For deeper NEC training on residential load calculation and service sizing, Mike Holt's NEC courses are the industry standard.
Working from the printed code? NEC code books and tab sets are available from Mike Holt.
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