Which NEC edition does this calculator use?

The calculator implements the Standard Method per NEC 2023 (NFPA 70) Article 220 with specific references to 220.12, 220.42, 220.52, 220.53, 220.54, 220.55 and 220.60.

Are small-appliance and laundry circuits included with general lighting for demand?

Yes. Per 220.52, each required small-appliance/laundry circuit is 1,500 VA and included with the general lighting load when applying Table 220.42 demand factors.

How are fixed appliances treated?

Per 220.53, if there are four or more fastened-in-place appliances (excluding range, dryer and space-conditioning), apply a 75% demand factor to their combined nameplate VA. Otherwise use 100%.

How is a single range handled?

For a single household range, demand is the nameplate rating per Table 220.55 and notes. This tool treats a single range accordingly.

Is this calculation sufficient for permitting?

This tool follows the NEC, but jurisdictions may have amendments and plan reviewers may require additional documentation. Always verify with your AHJ (Authority Having Jurisdiction).

NEC Service Load Calculator (Dwelling)

Q: Do I include both heating and cooling?

No. Per 220.60, only the larger of the heating or cooling load is included (not both at the same time).

Q: How is the dryer demand computed?

Per 220.54, a single residential dryer is calculated at 5,000 VA or the nameplate rating, whichever is greater, at 100%.

This professional-grade calculator implements the Standard Method from the 2023 National Electrical Code (NEC) Article 220 to estimate a dwelling unit’s service load. It’s designed for electricians, engineers, and plan reviewers who need a transparent, code-referenced result that is ready for documentation and permit submittals.

Input — Dwelling Unit Data

Service voltage (L-L)

Used to convert total VA to service amperes.

Habitable floor area (ft²) *

Per NEC 220.12(A), use 3 VA/ft² for dwelling units. Include habitable area; exclude garages, porches, patios, etc., unless finished and conditioned per local rules.

Small-appliance branch circuits (count) *

Per 210.11(C)(1) and 220.52(A), provide at least two 20 A small-appliance circuits in kitchens/dining/pantry. Each counts as 1,500 VA and is included with general lighting for demand.

Laundry branch circuits (count)

Per 210.11(C)(2) and 220.52(B), at least one 20 A laundry circuit is required for a dwelling. Each is 1,500 VA and included with general lighting for demand.

Fixed appliances (excluding range, dryer, space-conditioning)

Examples: dishwasher, disposal, microwave, water heater, well pump. Per 220.53, if you have four or more fastened-in-place appliances, apply 75% to their combined nameplate VA; otherwise use 100%.

Cooking appliance — range (kW)

Per 220.55 Table and notes: for a single household range, use the nameplate at 100%. For multiple ranges, use Table 220.55; multi-range diversity is not implemented in this version.

Clothes dryer (VA)

Per 220.54: a single residential dryer is calculated at 5,000 VA or the nameplate rating, whichever is larger, at 100%.

Space-conditioning (use the larger per 220.60)

Enter both if known. Per 220.60, include only the larger of the noncoincident heating or cooling load (not both).

Cooling equipment (VA)

Electric space heat or strip heat (VA)

Results — Standard Method (NEC 2023 Article 220)

General lighting load (3 VA/ft²)

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Small-appliance circuits (1,500 VA each)

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Laundry circuits (1,500 VA each)

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Subtotal for Table 220.42 demand

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Table 220.42 demand applied

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Fixed appliances (220.53) demand

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Range demand (220.55)

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Dryer demand (≥5,000 VA) (220.54)

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Space-conditioning (larger of heat/cool) (220.60)

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Total calculated load

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Service voltage

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Calculated service current

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Recommended minimum standard rating

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Data Source and Methodology

Authoritative Data Source: NFPA 70 — National Electrical Code (NEC), 2023 Edition. Primary references: Article 220 (220.12, Table 220.42, 220.52, 220.53, 220.54, 220.55 including notes, and 220.60). Official publisher: National Fire Protection Association (NFPA). Access the code: https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70

Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

Additional practitioner references consulted for clarity and interpretation include training materials from Mike Holt Enterprises and various jurisdictional handouts. Always verify local amendments with your AHJ.

The Formula Explained

General lighting load:

1) A_dwell = 3 · A_{ft^2}

2) S_{SA} = 1500 · N_{SA}, S_{L} = 1500 · N_{L}

3) S_{GL,subtotal} = A_{dwell} + S_{SA} + S_{L}

4) Table 220.42 demand:

D_{GL} = { 100% · S_{GL,subtotal}, if S_{GL,subtotal} ≤ 3000 } { 3000 + 35% · (S_{GL,subtotal} - 3000), if 3000 < S_{GL,subtotal} ≤ 120000 } { 3000 + 0.35 · 117000 + 25% · (S_{GL,subtotal} - 120000), if S_{GL,subtotal} > 120000 }

Fixed appliances (excluding range/dryer/HVAC):

D_{APPL} = { 1.00 · Σ VA, if count ≤ 3 } { 0.75 · Σ VA, if count ≥ 4 }

Range (single household range): D_{RNG} = VA_{nameplate}

Dryer: D_{DRY} = max(5000, VA_{nameplate})

HVAC: D_{HVAC} = max(VA_{cooling}, VA_{heating})

Total load: S_{TOTAL} = D_{GL} + D_{APPL} + D_{RNG} + D_{DRY} + D_{HVAC}

Service current: I_{service} = S_{TOTAL} / V_{LL}

Glossary of Variables

A_ft² — Habitable floor area in square feet.
N_SA — Number of small-appliance branch circuits (min 2), 1,500 VA each.
N_L — Number of laundry branch circuits, 1,500 VA each.
D_GL — General lighting demand after Table 220.42 factors.
Σ VA (appliances) — Sum of nameplate VA for fixed appliances (excludes range, dryer, HVAC).
D_APPL — Demand for fixed appliances per 220.53 (75% if 4+ appliances).
D_RNG — Range demand per 220.55 (single range = nameplate).
D_DRY — Dryer demand, minimum 5,000 VA or nameplate if larger (220.54).
D_HVAC — Larger of heating or cooling (220.60).
S_TOTAL — Total calculated load in volt-amperes (VA).
V_LL — Service voltage, line-to-line (e.g., 240 V).
I_service — Calculated service current in amperes.

Worked Example — “How It Works: A Step-by-Step Walkthrough”

Inputs: Area 1,800 ft²; small-appliance circuits 2; laundry circuits 1; fixed appliances: dishwasher 1,200 VA, disposal 800 VA, microwave 1,500 VA, water heater 4,500 VA; one range 12 kW; one dryer 5,000 VA; cooling 4,500 VA; electric heat 8,000 VA; service voltage 240 V.

General lighting = 3 × 1,800 = 5,400 VA. SA+Laundry = 1,500 + 1,500 + 1,500 = 4,500 VA. Subtotal = 9,900 VA.
Apply Table 220.42: 3,000 @ 100% + 6,900 @ 35% = 3,000 + 2,415 = 5,415 VA.
Fixed appliances: total = 1,200 + 800 + 1,500 + 4,500 = 8,000 VA. Four appliances → 75% → 6,000 VA.
Range: single, 12 kW → 12,000 VA.
Dryer: max(5,000, nameplate) = 5,000 VA.
HVAC: larger of 4,500 and 8,000 = 8,000 VA.
Total S_TOTAL = 5,415 + 6,000 + 12,000 + 5,000 + 8,000 = 36,415 VA. I_service = 36,415 / 240 ≈ 151.7 A. Recommend next standard ≥ 152 A → 175 A (often specified as 200 A for margin and future capacity).

Frequently Asked Questions (FAQ)

Does this tool use the Standard Method or the Optional Method?

This calculator implements the Standard Method per NEC 2023 Article 220. Optional Method (220.82) may yield lower loads for qualifying dwellings; it will be offered in a separate tool.

Can I use this for multifamily units?

Yes, but ensure your inputs (e.g., voltage, shared equipment, house loads) match the specific dwelling unit. Feeder/service sizing for multifamily services requires additional steps.

How are kitchen appliance receptacles covered?

They are accounted for by the required small-appliance circuits at 1,500 VA each per 220.52(A), included with general lighting for demand per Table 220.42.

What if my range is over 12 kW or I have multiple ranges?

NEC Table 220.55 with Notes provides diversity for multiple or large ranges. This version treats a single range at nameplate; multi-range diversity will be added in a future release.

Do I include both heating and cooling?

No. Per 220.60, include only the larger of the two noncoincident loads.

Why might AHJs produce slightly different numbers?

Local amendments, interpretation of floor area, appliance classification, and rounding conventions can vary. Provide your assumptions and code cites with the submittal.

Is this a substitute for stamped engineering?

No. Use it as a code-based estimate. For complex projects, consult a licensed professional engineer or master electrician.

Tool developed by Ugo Candido. Content verified by CalcDomain Editorial Team.
Last reviewed for accuracy on: September 14, 2025.