6.3 Optional Methods: Single Dwelling, Existing Dwelling & Multifamily (2026 NEC 120.82–120.85)

When to use the optional method

The optional calculations in Article 120 (formerly Part IV of Article 220) let you size a feeder or service from total connected load with large demand factors. They recognize that a dwelling never runs every appliance at once. On the exam, read the question: if it says "using the optional method," apply 120.82 or 120.84; otherwise use the standard method.

Single dwelling unit (120.82)

Eligibility (120.82(A))

The dwelling must be served by a single 120/240 V or 208Y/120 V, 3-wire set of service or feeder conductors with an ampacity of 100 A or greater. The neutral may still be calculated under 120.61.

General loads (120.82(B))

Add the following and take the first 8 kVA at 100% plus 40% of the remainder (2026 NEC; the 2023 edition used the first 10 kVA):

1. General lighting: 2 VA/ft² (2026 NEC; formerly 3 VA/ft²), with floor area per 120.5(C).
2. Small-appliance and laundry circuits: 1,500 VA for each 20 A small-appliance circuit (at least two) and each laundry circuit (at least one).
3. Appliances at nameplate: appliances fastened in place, permanently connected, or on a specific circuit; ranges, wall ovens, and counter-mounted cooking units; clothes dryers not connected to the laundry circuit; and water heaters.
4. Motors: nameplate rating of permanently connected motors not already included.

Note that the range and dryer are added at nameplate here, not from Tables 120.55 and 120.54.

Heating and air conditioning (120.82(C))

Include the largest of these:

EVSE (120.82(D))

New in 2026: add 100% of the EVSE nameplate rating, calculated as in 120.57, with no demand factor. EVSE is a large, long-duration load, so it is no longer reduced with the general loads.

Worked example: the same 2,000 ft² house

The house from the standard-method section has a 12 kW range, 5.5 kW dryer, 4.5 kW water heater, 1.2 kW dishwasher, 0.8 kW disposal, 1.5 kW built-in microwave, 10 kW electric furnace, 5 kVA A/C, and 9.6 kW EVSE.

1. General loads: $4000 + 3000 + 1500 + 12{,}000 + 5500 + 4500 + 1200 + 800 + 1500 = 34{,}000$ VA.
2. Demand: $8000 + (34{,}000 - 8000) \times 0.40 = 8000 + 10{,}400 = 18{,}400$ VA.
3. Heating or cooling: A/C at 100% = 5,000 VA; one electric furnace at 65% = 6,500 VA. Use 6,500 VA.
4. EVSE: 9,600 VA.
5. Total: $18{,}400 + 6500 + 9600 = 34{,}500$ VA, and $34{,}500 \div 240 = 143.75$ A.

The optional method supports a 150 A service, while the standard method required 200 A for the same house.

Existing dwelling units (120.83)

Section 120.83 (formerly 220.83) provides an optional way to decide whether an existing dwelling service can carry added loads, such as a heat pump or EVSE. The 2026 edition consolidated the older two-part method into a single Table 120.83, uses the 2 VA/ft² lighting load, and adds demand factors for new loads such as EVSE. Section 120.87 also allows existing loads to be based on the maximum demand data for one year, with conditions.

Multifamily dwellings (120.84)

Conditions (120.84(A))

The optional multifamily calculation may be used for a building of three or more units only when all of these are true:

1. no dwelling unit is supplied by more than one feeder;
2. each unit has electric cooking equipment; and
3. each unit has electric space heating, air conditioning, or both.

House loads, such as corridor lighting and elevators, are calculated by the standard method and added to the Table 120.84 result (120.84(B)).

Table 120.84 demand factors

The table continues down to 23% for 62 or more units. The connected load for each unit includes its general lighting, small-appliance and laundry circuits, appliances at nameplate, and the larger of heating or air conditioning.

Two dwelling units (120.85): where a feeder serves two units and the standard calculation exceeds the optional result for three identical units, the lesser of the two loads may be used.

Example: a 10-unit building in which each unit has a total connected load of 40 kVA: $10 \times 40 = 400$ kVA; Table 120.84 for 8 to 10 units is 43%, so the demand is $400 \times 0.43 = 172$ kVA, plus the house loads.