Show Window & Sign Lighting Load Calculator
Calculate the show-window and sign/outline-lighting lines of a commercial NEC Article 220 service or feeder. Enter the show window length and the number of required sign circuits; the tool applies the 220.43(A)/220.14(G) 200 VA per linear foot and the 220.14(F) 1200 VA per-circuit minimum, reports the 100% calculated load, the 125% continuous figure, and the amperes.
How to use this calculator
- Enter the show window length in linear feet, measured horizontally along its base (NEC 220.43(A)/220.14(G), 200 VA/ft). Enter 0 if there is no show window.
- Enter the number of required sign circuits. NEC 600.5(A) requires at least one sign/outline lighting outlet per pedestrian-accessible commercial occupancy, and NEC 220.14(F) calculates 1200 VA minimum for each.
- Optionally enter the actual sign load in VA if it is larger than the 1200 VA-per-circuit minimum; leave it blank to use the minimum.
- Pick the voltage and phase of the feeder or panel for the demand-current readout.
- Read the calculated load in volt-amperes and its amperes. The tool shows the show-window load, the sign load, the total at 100%, and the 125% continuous figure used for conductor and service sizing.
NEC reference
This calculator follows the National Electrical Code (NEC) 2020. Section 220.43(A) sets the show-window feeder/service load at 200 volt-amperes per linear foot of show window, and Section 220.14(G) applies the same value to the branch circuit. Section 220.14(F) requires a minimum of 1200 volt-amperes for each required sign or outline lighting branch circuit (Section 600.5(A) requires the outlet). Show-window and sign loads are calculated at 100% (no demand factor) and are continuous loads, so conductors and overcurrent devices are sized at 125% of them.
Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.
Show window and sign load values (NEC 2020)
Both loads are fixed volt-ampere allowances. The show window is measured horizontally along its base; a full-height display window and a shallow one at the same width carry the same load. The sign allowance is per required branch circuit, not per sign face.
| Load | NEC section | Allowance |
|---|---|---|
| Show window (feeder/service) | 220.43(A) | 200 VA / ft |
| Show window (branch circuit) | 220.14(G) | 200 VA / ft |
| Sign / outline lighting | 220.14(F) | 1200 VA / circuit |
Values are NEC 2020. The 200 VA/ft and 1200 VA figures are long-standing; only the section numbering has moved across editions.
Worked example: a retail tenant
A strip-mall tenant has a 20-foot show window and one required sign circuit. The show-window load is 20 × 200 = 4000 VA, and the sign load is 1 × 1200 = 1200 VA, for a total calculated load of 5200 VA at 100%. Because both are continuous loads, the service-entrance conductors and overcurrent device are sized at 125%: 5200 × 1.25 = 6500 VA. On a 120 V circuit the base load draws 5200 / 120 = 43.3 A. The widely published EC&M and ExpertCE show-window example uses the same method: a 10-foot window is 10 × 200 = 2000 VA, and 2000 × 125% = 2500 VA when sizing the service-entrance conductors.
Why no demand factor applies
The Table 220.42 demand factors reduce the general lighting load of certain occupancies, and Table 220.44 reduces the general-use receptacle load, on the diversity assumption that not everything runs at once. Show-window and sign lighting are specific loads that the NEC adds at their full calculated value, so no demand factor is taken. They are, however, continuous loads, which is why the 125% continuous multiplier is the relevant adjustment when sizing the conductor and overcurrent device.
What this tool does not do
- Track lighting (NEC 220.43(B)). Track lighting is calculated at 150 VA per 2 ft of track in other-than-dwelling occupancies, a separate provision from the show-window load.
- Conductor, overcurrent device, and neutral sizing. The tool reports the 125% continuous load but selects no wire or device. Size those with the Wire Size, Service Size, Breaker Size, and Neutral Load calculators (NEC 210.19, 240.4, Table 310.16, 220.61).
- The whole-building service calculation. Show-window and sign loads are two lines of an Article 220 Part III calculation; add general lighting, receptacle, and kitchen loads with the Commercial Load Calculator.
- The 180 VA-per-outlet branch option. This tool uses the 200 VA/ft basis, the only method 220.43(A) allows for feeders and services.
Frequently asked questions
Is the show window measured by height or width?
Width. NEC 220.43(A) measures show window length horizontally along its base, so only the linear feet across the window matter. A tall window and a short one of the same width carry the same 200 VA per foot.
Does every commercial space need a 1200 VA sign load?
NEC 600.5(A) requires at least one sign or outline lighting outlet at each commercial building and each occupancy accessible to pedestrians at ground level, and NEC 220.14(F) calculates that required circuit at a minimum of 1200 VA. A space without a pedestrian entrance at grade may not require the outlet; enter 0 sign circuits in that case.
Is this the same as the whole commercial service calculation?
No. This computes only the show-window and sign lines. A full commercial service calculation adds general lighting, receptacles, kitchen equipment, and more. Use the Commercial Load Calculator for the complete service size.
Related calculators
- Commercial Load Calculator: the full NEC 220 Part III non-dwelling service calculation that folds in show-window and sign loads.
- Commercial Receptacle Load Calculator: the general-use receptacle line per 220.14(I) and Table 220.44.
- Commercial Kitchen Equipment Demand Calculator: the Table 220.56 kitchen equipment demand line.
- Service Size Calculator: minimum service disconnect, conductor, and grounding electrode conductor from a known load.
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