Commercial Load Calculator — NEC 220 Part III

By the Article 220 Part III standard method, in four groups. General lighting is floor area × the VA per square foot for the occupancy, then a Table 220.42 demand factor. Receptacles are 180 VA per strap, then the Table 220.44 factor — first 10 kVA at 100%, the rest at 50%. Show window and track lighting are per-foot rules that get no demand factor at all. Everything else — HVAC, motors, dedicated equipment — lands at 100%. Add the four, divide by the system voltage, and you have the minimum service.

No, and this is the single most common misunderstanding. NEC 220.82 is a dwelling-only shortcut — it says so in its own title. There is no commercial equivalent, so the Part III standard method is not one option among several for a non-dwelling; it is the calculation. Part IV contains a few narrow optional methods for specific occupancies such as schools and restaurants, but they are exceptions with their own conditions, not a general shortcut.

It depends on the occupancy, and on which code cycle you are working to. The long-standing figures are 3 VA/ft² for stores and schools, 3.5 for offices and banks, 2 for restaurants, hotels and hospitals, 0.5 for commercial garages, and 0.25 for warehouses. Those are the values preloaded here. NEC 2020 rewrote Table 220.12 around energy-code lighting densities and its numbers are generally lower — an office dropped to roughly a third of the old figure. The VA/ft² field is directly editable for exactly that reason.

At 180 VA per strap, under 220.14(I). A strap — a yoke — is the mounting device, so a duplex receptacle counts once, not twice. A quad on two straps counts twice. Then Table 220.44 applies: the first 10,000 VA at 100% and everything above at 50%. That crossover matters more than people expect. Below about 55 straps there is no reduction at all; a 200-strap office sees its 36,000 VA fall to 23,000.

Because they are already sized to what is actually installed rather than to a statistical average. 220.43(A) requires 200 VA per linear foot of show window, and 220.43(B) requires 150 VA for every 2 feet of track. Both are lighting loads that run at full output during business hours — the textbook continuous load — so there is nothing to diversify. They sit alongside the general lighting load, not inside it.

In a dwelling, yes — 220.14(J) folds general-use receptacles into the 3 VA/ft², which is why there is no NEC limit on outlets per circuit in a house. In a non-dwelling, no. Commercial receptacles are counted separately at 180 VA per strap under 220.14(I). This is the structural difference between the two calculations, and mixing them up either doubles the receptacle load or drops it entirely.

The cooking equipment is not. NEC 220.56 gives commercial kitchen equipment its own demand factors — 100% for one or two units, 90% for three, 80% for four, 70% for five, and 65% for six or more — with a floor: the result may never be less than the sum of the two largest pieces. Note that this is entirely separate from Table 220.55, which applies only to household ranges. Enter the kitchen equipment demand into the other-loads field here.

Yes. 220.50 routes motor loads to Article 430, and 430.24 requires the feeder to carry 125% of the largest motor's full-load current plus the full-load current of the rest. That 25% adder is not part of the Part III arithmetic and has to be added separately. Size the motors first with the Motor Circuit Calculator, then bring the total into the other-loads field.