Load calculation · NEC 220

Electrical Load Calculator

Estimate residential and commercial electrical service and feeder loads using NEC Article 220 standard method. Enter building area, appliances, HVAC, and other loads to compute total demand in volt-amps and amps.

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NEC 220 standard
Residential & commercial
Demand factors applied

Load calculation

NEC Article 220 · Standard Method

Formula

Total VA = Σ (Demand-adjusted loads)

Field inputsLoad calculation

Method: NEC 220
Demand: Table 220.42
Output: VA + Amps
Service: Suggested size

Estimate total demand and suggested service size before pulling a permit.

Building & load inputs

Describe the occupancy and loads

Occupancy type

Floor area (sq ft)

Small-appliance circuits

Laundry circuits

System voltage (V)

Major appliance loads (VA)

Electric range (VA)

Electric dryer (VA)

Water heater (VA)

HVAC / AC (VA)

Other loads (VA)

Other continuous loads

Other non-continuous loads

Assumptions: NEC 220.12 general lighting VA per sq ft; small-appliance circuits at 1,500 VA each per 220.52(A); laundry at 1,500 VA per 220.52(B); dwelling demand factors from Table 220.42; range demand per Table 220.55; continuous loads at 125% for non-dwelling per 210.20(A). This is a simplified standard-method estimate. Always verify against the current NEC and your AHJ.

Load calculation result

Total demand

100 A service

Total calculated load

23,125 VA (96.4 A)

General lighting & receptacles: 6,000 VA
Small-appliance circuits: 3,000 VA
Laundry circuit(s): 1,500 VA
General demand (100% of first 3,000 VA + 35% of remainder): 5,625 VA
Range demand: 8,000 VA
Dryer demand: 5,000 VA
Water heater demand: 4,500 VA
HVAC demand: 0 VA
Other continuous (incl. 125%): 0 VA
Other non-continuous: 0 VA

Suggested service size

Total 96.4 A → 100 A panel

Source: NEC Article 220, Tables 220.12, 220.42, 220.55. Dwelling unit standard method.

Safety & accuracy notice

This electrical load calculator is a planning aid only. It is not engineering, a permit, or design approval, and it is not legal or code certification. Results are estimates based on the NEC standard method.

Always verify against the current adopted NEC (National Electrical Code), equipment listings and manufacturer instructions, and your local AHJ (Authority Having Jurisdiction — the inspector or department that enforces the code). Final load calculations should be reviewed and approved by a licensed electrician or professional engineer.

Electrical load calculation FAQ

What is the standard method for calculating dwelling unit load per NEC 220?

NEC 220.40 requires the total load to include general lighting and receptacles (3 VA per sq ft per Table 220.12), small-appliance branch circuits (1500 VA each, minimum 2), laundry circuit (1500 VA), and then either the standard or optional calculation method for ranges, dryers, HVAC, and other loads. The standard method applies a demand factor from Table 220.42 to the first 3000 VA at 100% and the remainder at 35%.

How is commercial load calculated differently from residential?

Commercial occupancies use NEC Article 220, Part III (feeder and service load calculations). General lighting is from Table 220.12 based on occupancy type. Receptacle loads are calculated at 180 VA per outlet per 220.14(I) and (L), with demand factors from Table 220.44 for the portion over 10 kVA. Continuous loads must be calculated at 125% of the actual load per 210.20(A) and 215.3.

Is this calculator a substitute for engineering?

No. It is a planning aid only — not engineering, a permit, or design approval. Always verify against the current adopted NEC and your local AHJ.

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Next steps after load calculation

Use the load total to size your service, pick conductors, and schedule your panel.

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Size the conductor against both ampacity and your voltage-drop limit.

Voltage drop calculator

Check voltage drop on the feeder or branch circuit supplying the load.

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Wire ampacity reference

Look up NEC Table 310.16 ampacity by wire size, insulation, and temperature rating.

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