Commercial Feeder and Service Load Calculator
Estimate a commercial building service or feeder load and review a separate preliminary conductor-sizing basis.
Building and connected loads
Follow Table 120.42(A) notes. For example, banks use Office and stores use Retail.
Use the floor area covered by the selected occupancy. Calculate separate areas separately for mixed occupancies.
Enter connected lighting load that is not expected to operate for 3 hours or more.
Enter connected lighting load expected to operate for 3 hours or more.
Receptacles
Uses 180 VA per receptacle yoke before the selected demand factor.
Uses 180 VA per 5 ft, or per 1 ft when simultaneous use is likely.
Applies 100% to the first 10 kVA and 50% to the remainder.
Display and track lighting
Calculated at 200 VA per linear foot.
Calculated at 1,200 VA per circuit.
Calculated at 150 VA for each 2 ft or fraction thereof.
Select when the load is expected to operate for 3 hours or more.
Heating, cooling, and other equipment
Enter the equipment load after applying equipment-specific calculation rules.
Enter the equipment load after applying equipment-specific calculation rules.
Select when the load is expected to operate for 3 hours or more.
Enter loads after applying their applicable demand factors. Exclude categories already entered above.
Enter connected loads expected to operate for 3 hours or more. Exclude loads entered above.
Motor and supply
Use the applicable table full-load current for the feeder motor group. Include the motor's running load above only once.
The equivalent line-current result assumes a balanced load for the selected phase.
Calculated load
The Article 120 load and the preliminary conductor-sizing basis are shown separately. Current is an equivalent line-current estimate for a balanced supply.
About this calculator
This worksheet estimates a common non-dwelling service or feeder load from occupancy, lighting, receptacles, display lighting, HVAC, motors, and other equipment. It reports the calculated load separately from a preliminary conductor-sizing basis.
Use one occupancy type per calculation. For a mixed-use building, calculate each occupancy area and load group separately, then have the combined worksheet reviewed under the adopted code.
Method and assumptions
The occupancy lighting minimum is floor area multiplied by the selected Table 120.42(A) unit load. The lighting load is the greater of that minimum or the entered actual connected lighting load. The office receptacle load is the greater of its demand-adjusted load or 1 VA per square foot.
General-use receptacles are calculated at 180 VA per yoke. Fixed multioutlet assemblies use 180 VA for each 5 ft or fraction, or each 1 ft or fraction when simultaneous use is likely. The selected demand factor applies 100% to the first 10 kVA and 50% to the remainder.
The worksheet calculates show-window lighting at 200 VA per linear foot, outside sign circuits at 1,200 VA each, and track lighting at 150 VA for each 2 ft or fraction. HVAC uses the larger heating or cooling load when they cannot operate together, or their sum when they can.
The conductor-sizing basis starts with the calculated load. It separately adds 25% for selected continuous loads and 25% of the largest motor full-load current converted to VA at its entered phase and voltage. The occupancy lighting minimum is not increased again when it exceeds the entered actual lighting load.
Other equipment fields must contain calculated loads after applicable demand factors. Apply any special equipment rules before entering those totals. This worksheet does not cover every service, feeder, motor, HVAC, kitchen, healthcare, emergency, or mixed-occupancy provision.
Example
For a 4,800 ft² retail area, the lighting minimum is 9,120 VA at 1.9 VA/ft². Eighty receptacle yokes start at 14,400 VA and calculate to 12,200 VA after the selected demand factor. A 30 ft show window adds 6,000 VA, and one outside sign circuit adds 1,200 VA. With no other entered loads, the calculated load is 28,520 VA. The conductor-sizing basis is 30,320 VA after the 25% show-window and sign adjustments.
This example checks the arithmetic only. Confirm the applicable method, continuous-load treatment, service and feeder rules, and locally adopted edition for the actual project.
Interpret the results
The calculated load is the sum of the supported categories after the selected demand factors. The equivalent current assumes a balanced load across the selected supply voltage and phase.
The conductor-sizing basis is a screening value for review. Actual conductor ampacity and overcurrent protection also depend on wiring method, terminal temperature ratings, adjustment and correction factors, equipment, load characteristics, and the authority having jurisdiction.
FAQs
What does this worksheet calculate?
It totals supported non-dwelling load categories and estimates balanced line current. It also shows a separate preliminary conductor-sizing basis that accounts for selected continuous loads and the entered largest motor.
Why are calculated load and conductor-sizing basis different?
The load calculation and conductor ampacity rules do not apply every adjustment at the same step. The worksheet keeps the Article 120 load separate from selected 125% continuous-load adjustments and the largest-motor adder used for a preliminary conductor basis.
How should I enter equipment loads?
Enter each equipment group after applying its applicable calculation or demand factor. Do not include a load in more than one field. For motors, include the running load in an equipment category and enter the largest motor full-load current separately for the sizing adder.
How does the office receptacle minimum work?
For the office occupancy, the worksheet uses the greater of the receptacle load after the selected demand factor or 1 VA per square foot.
What if this building has more than one occupancy?
Calculate each occupancy area separately and combine the results in a reviewed worksheet. This tool applies one occupancy type to the entered floor area.
Does this select service conductors or an overcurrent device?
No. The conductor-sizing basis is an intermediate estimate only. It does not select conductor size, service rating, overcurrent protection, equipment, or neutral sizing.
Can I use this for restaurants, hospitals, or other special occupancies?
Use the supported occupancy lighting unit load as one input, but review all special occupancy, kitchen, HVAC, motor, emergency, and other applicable rules separately. The worksheet does not implement every Article 120 method or exception.
Sources
- NFPA 70, National Electrical Code, 2026 edition — Articles 120, 215, 230, and 430; verify the full adopted text and local amendments.
- NFPA 70 Second Draft Report, preliminary report — public code-development material used to cross-check the worked load example and assumptions.