How is a mobile home load calculation different from a regular dwelling calculation?

The biggest difference is the lighting basis. NEC 550.18(A)(1) computes general lighting as 3 VA per square foot of the mobile home’s outside dimensions (length times width, excluding the towing coupler), not the habitable floor area a standard Article 220 dwelling calculation uses. Because the outside footprint is larger than the habitable area, running a mobile home through a general dwelling calculator understates the lighting load. The rest of 550.18 mirrors the standard method: 1500 VA per small-appliance and laundry circuit, the first 3000 VA at 100% with the remainder at 35%, Table 220.55 for cooking, 220.54 for the dryer, the larger of heating or air conditioning, and 25% of the largest motor.

What is the minimum service size for a mobile home?

NEC 550.32(C) requires the mobile home service equipment to be rated not less than 100 amperes, so the calculator never recommends a service below 100 A even when the calculated load is smaller. The calculated load still matters: if it exceeds 100 A, the recommended service steps up to the next standard 240.6(A) rating (125, 150, 200 A, and so on).

How does this calculator handle an electric range?

The cooking load uses NEC Table 220.55 Column C, the same demand table the standard dwelling method uses. One household range not over 12 kW is an 8 kW demand regardless of the exact nameplate. For ratings over 12 kW through 27 kW, Note 1 adds 5% to the 8 kW for each kilowatt above 12, so a 16 kW range is 8 kW times 1.20, or 9.6 kW. Set the range count to zero for a gas range.

Does this cover a mobile home park feeder or service?

No. This tool sizes the supply for a single mobile or manufactured home. A mobile home park service or feeder uses NEC 550.31 and Table 550.31, which allow at least 16,000 VA per lot with a demand factor that decreases as the number of lots grows. That park calculation is a separate tool and is not applied here.

Mobile Home Electrical Load Calculator

Size the service or feeder assembly for a single mobile or manufactured home by the NEC 550.18 method. Lighting is figured on the home's outside dimensions (not habitable floor area), then Table 220.55 cooking, the 220.54 dryer, noncoincident heating and air conditioning, and the largest-motor adder are layered on. The recommended service honors the 100 A minimum of NEC 550.32(C).

Home size (outside dimensions, NEC 550.18(A))

Length (ft, outside)

Width (ft, outside)

Use the home's outside length and width (excluding the towing coupler), not the habitable floor area. Lighting is 3 VA/ft² of that footprint per 550.18(A)(1).

20 A small-appliance circuits

Laundry circuits

Fixed appliances (NEC 220.53, 75% for four or more)

Total nameplate VA (water heater, dishwasher, disposal, etc.)

Number of fixed appliances

Count fastened-in-place appliances only, not the range, dryer, heat, or A/C (those are handled below). Four or more triggers the 75% demand factor.

Cooking and laundry (NEC Table 220.55 / 220.54)

Household ranges / cooking units

Each rated (kW)

Electric dryer nameplate (VA)

Set range count to 0 for a gas range. The dryer takes 5000 VA or the nameplate, whichever is larger (220.54).

Heating, A/C and motors (NEC 220.60 / 430.24)

Air conditioning (VA)

Electric space heat (VA)

Largest motor (VA)

Heat and A/C are noncoincident, so only the larger is counted. The largest motor (often the A/C compressor) adds 25% per 430.24.

How to use this calculator

Enter the home's outside length and width from the data plate, excluding the towing coupler. The tool multiplies the footprint by 3 VA/ft² for general lighting per 550.18(A)(1).
Set the small-appliance circuits (two minimum) and laundry circuits at 1500 VA each. Total the nameplate VA of the fixed appliances that are not the range, dryer, heat, or A/C, and enter how many there are; four or more gets the 220.53 75% factor.
Enter the range count and each unit's kW rating (zero for a gas range), plus the electric dryer nameplate. The tool applies Table 220.55 Column C and the 5000 VA dryer minimum automatically.
Enter heating and A/C nameplates (only the larger is counted) and the largest motor. Read the calculated amps and the recommended service, which is floored at the 100 A mobile-home minimum.

NEC reference

This calculator implements the NEC 2020 550.18 calculation for a single mobile or manufactured home: general lighting at 3 VA/ft² of the outside dimensions plus small-appliance and laundry circuits at 1500 VA each (550.18(A)), reduced by the first-3000-VA-at-100%, remainder-at-35% demand; fastened-in-place appliances at 75% for four or more (220.53); the electric dryer at 5000 VA or nameplate (220.54); household cooking per Table 220.55 Column C with Note 1; heating and air conditioning as noncoincident loads (220.60); and 25% of the largest motor (430.24). The recommended service is the smallest 240.6(A) rating at or above the calculated amps, floored at the 100 A mobile-home service minimum (550.32(C)). It sizes one home; a mobile home park (550.31, Table 550.31) is out of scope.

Results are for reference only. Verify against the applicable adopted edition of the NEC and consult a licensed electrician for code compliance.

Worked example: 70 × 14 all-electric manufactured home

These are the same numbers the calculator produces from its default inputs, so you can verify the tool against the worksheet directly. The 70 × 14 footprint is 980 ft², so lighting is 980 × 3 = 2940 VA.

Category	Basis	Demand VA
Lighting, small-appliance, laundry	7440 VA connected, 550.18(A): 3000 + 4440 × 0.35	4,554
Fixed appliances (3, so 100%)	6000 VA × 1.00 (220.53)	6,000
Electric dryer	max(5000, nameplate) (220.54)	5,000
Range, 12 kW	Table 220.55 Column C, one unit	8,000
Heat vs A/C	max(8000 heat, 5000 A/C) (220.60)	8,000
Largest motor, 25%	0 VA entered × 0.25 (430.24)	0
Total		31,554

31,554 VA ÷ 240 V = 131.5 A, so a 150 A minimum standard rating (a 200 A service is commonly installed for headroom). Add the A/C compressor's nameplate to the largest-motor field to include its 25% adder, which this default leaves at zero.

Frequently asked questions

Why use outside dimensions for the lighting load?

NEC 550.18(A)(1) is explicit: the general lighting load for a mobile or manufactured home is 3 VA per square foot of the home's length times width, taken from the outside dimensions and excluding the towing coupler. That gross footprint is larger than the habitable floor area a standard Article 220 dwelling calc uses, so feeding a mobile home into a general house calculator understates the lighting. This tool asks for the two data-plate dimensions and uses the outside footprint directly.

What is the smallest service a mobile home can have?

100 amperes. NEC 550.32(C) fixes 100 A as the minimum rating for mobile home service equipment, so even a small home with a modest calculated load lands on a 100 A service. When the calculated load climbs past 100 A, the tool steps the recommendation up to the next standard 240.6(A) rating (125, 150, 175, 200 A, and so on).

When does the 75% appliance factor apply?

NEC 220.53, applied inside the 550.18(B) supply total, lets you take fastened-in-place appliances at 75% of their combined nameplate only when there are four or more of them, and it excludes the range, dryer, space heating, and A/C, which have their own categories. Three or fewer fixed appliances are taken at 100%. Enter the count so the tool applies the right factor.

Can I use this for a mobile home park?

Not yet. This calculator sizes one home's supply. A park service or feeder uses NEC 550.31, which permits at least 16,000 VA per lot with a demand factor that falls as lot count rises (Table 550.31). That per-lot park calculation is planned as a separate tool; for now, size each home here and apply the park demand factors by hand.

Related calculators

Residential Electrical Load Calculator runs the Article 220 standard method for a site-built dwelling on habitable floor area.
Electrical Load Calculator covers the optional method (220.82) for a single dwelling.
Wire Size Calculator sizes the service and feeder conductors for the calculated load.
Breaker Size Calculator sizes the individual branch circuits feeding these loads.

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For deeper NEC training on mobile home service and load sizing, Mike Holt's NEC courses are the industry standard.

Working from the printed code? NEC code books and tab sets are available from Mike Holt.

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Mobile home supply load (NEC 550.18)