In shortNEC 220.56 lets you apply a demand factor to commercial kitchen equipment when sizing feeders and services, on the reasoning that a kitchen's thermostatically controlled and intermittently used equipment never all draws full nameplate load at once. With six or more units, the demand factor drops to 65%, but the calculated demand can never be less than the sum of the two largest pieces of equipment.
That floor is where most errors happen, and it's the part an equipment schedule won't remind you about.
What the demand factors are
The demand factor steps down as the number of units increases:
| Number of units | Demand factor |
|---|---|
| 1–2 | 100% |
| 3 | 90% |
| 4 | 80% |
| 5 | 70% |
| 6 or more | 65% |
The section applies to commercial electric cooking equipment, dishwasher booster heaters, water heaters, and other kitchen equipment. It specifically does not apply to space heating, ventilating, or air-conditioning equipment. Those are calculated separately, which matters in a kitchen where the makeup air unit is often one of the largest loads in the room.
Verify these values against the NEC edition your jurisdiction has actually adopted before using them on a live project. Adoption lags publication, and local amendments exist.
Worked example: a quick-service restaurant
Take a QSR kitchen on a 208V three-phase service with six pieces of kitchen equipment:
| Equipment | Nameplate |
|---|---|
| Fryer 1 | 14 kW |
| Fryer 2 | 14 kW |
| Griddle | 12 kW |
| Convection oven | 11 kW |
| Dishwasher booster heater | 9 kW |
| Holding cabinet | 4 kW |
| Total connected | 64 kW |
Six units, so the 65% demand factor applies:
64 kW × 0.65 = 41.6 kW
Now apply the floor. The two largest loads are the two fryers, 14 kW each, totalling 28 kW. Our calculated demand of 41.6 kW is greater than 28 kW, so the demand factor result governs.
Converting to amps at 208V three-phase:
41.6 kW ÷ (√3 × 208 V) = 41,600 ÷ 360.3 = 115 A
So roughly 115 amps of kitchen equipment demand load feeds into the feeder calculation.
The case where the floor actually bites
Now change the equipment mix. Same six units, but two large ones and four small:
| Equipment | Nameplate |
|---|---|
| Combi oven | 20 kW |
| Combi oven | 20 kW |
| Four small appliances | 1 kW each (4 kW total) |
| Total connected | 44 kW |
Six units, so again 65%:
44 kW × 0.65 = 28.6 kW
But the two largest loads total 40 kW, and 28.6 kW is less than 40 kW. The floor governs, so you must use 40 kW, not 28.6 kW. At 208V three-phase that's 111 A instead of the 79 A the demand factor alone would have given you.
Miss that check and you've undersized the feeder by roughly 30%. It's a one-line check that takes ten seconds and it's skipped constantly, because the demand factor calculation feels like the whole job.
Where this fits in the service calculation
The kitchen equipment demand load is one input, not the answer. It joins lighting, receptacle, HVAC, refrigeration, signage, and any other loads in the overall Article 220 feeder and service calculation. In a restaurant, the interesting coordination problem is usually that kitchen equipment, refrigeration, and the makeup air unit each get calculated under different rules and then all land on the same service.
A practical sequencing note: kitchen equipment schedules change late and often. The equipment package frequently isn't finalised until well after the electrical design is developed, and a single swap from a 14 kW fryer to a 22 kW one can move the demand calculation enough to change the feeder. Build the calculation so it's easy to re-run, and re-run it when the equipment schedule is finally locked rather than assuming the early version held.
Frequently asked questions
Does NEC 220.56 apply to the makeup air unit or kitchen exhaust fan?
No. Space heating, ventilating and air-conditioning equipment are excluded from these demand factors and are calculated under their own provisions, which matters because in many commercial kitchens the makeup air unit is a substantial load.
Do I count a single piece of equipment with multiple elements as one unit or several?
It is counted as one unit of kitchen equipment. The unit count in the table refers to pieces of equipment, not heating elements or circuits.
Can demand factors be applied to a single large appliance?
No meaningful reduction: at one or two units the demand factor is 100%, so the calculation is simply the connected load.
Does this apply to residential kitchens?
No. Article 220.56 covers kitchen equipment other than in dwelling units. Household cooking appliance loads in dwellings are handled under a different section with a different method.
What voltage should a commercial kitchen service be?
That's a design decision, not a code answer, but 208V three-phase is common for smaller commercial kitchens in North America and 480V three-phase with step-down transformers for larger facilities, where the higher voltage reduces conductor sizes on long runs.
SYMATEQ produces NEC load calculations, feeder and service sizing and voltage drop for restaurant, QSR and commercial projects across the United States and Canada, including the re-runs when the equipment schedule changes.
Run the numbers yourself in the SYMATEQ Engineering Hub, see electrical design assist, or read about MEP engineering for restaurants and QSR.