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Dwelling Load Calculation

The standard (long) method from NEC Article 220, Part III. It looks long, but it's just a checklist: total the loads, apply the demand factors, divide by the voltage. Follow the order every time.

Example — 2,000 sq ft dwelling, 240 V service

Appliances: 12 kW range, 5 kW dryer, 4,500 W water heater, 1,200 W dishwasher, 900 W disposal.

Step 1 — General lighting & receptacles (Table 220.12, 3 VA/ft²):

2,000 ft² × 3 VA = 6,000 VA

Step 2 — Add small-appliance + laundry circuits (220.52):

2 small-appliance × 1,500 = 3,000 VA 1 laundry × 1,500 = 1,500 VA General-lighting group subtotal = 6,000 + 3,000 + 1,500 = 10,500 VA

Step 3 — Apply lighting demand factors (Table 220.42):

First 3,000 VA × 100% = 3,000 VA Remaining 7,500 VA × 35% = 2,625 VA Demand subtotal = 5,625 VA

Step 4 — Range (Table 220.55, Column C, one 12 kW range = 8 kW):

Range demand = 8,000 VA

Step 5 — Dryer (220.54, 5,000 VA min or nameplate):

Dryer = 5,000 VA

Step 6 — Fixed appliances (220.53): water heater 4,500 + dishwasher 1,200 + disposal 900. Only 3 fastened appliances (range/dryer counted separately), so the 75% factor does not apply — use 100%.

4,500 + 1,200 + 900 = 6,600 VA

Step 7 — Total and convert to amps:

5,625 + 8,000 + 5,000 + 6,600 = 25,225 VA 25,225 VA ÷ 240 V = 105.1 A

Calculated load ≈ 105 A → use a 125 A service (min. 100 A for a dwelling, 230.79)

Watch the 4-appliance rule: the 75% demand factor in 220.53 applies only when there are four or more fastened-in-place appliances. With three, you use the full 100%. Add a fourth (say, a built-in microwave) and the factor kicks in.

For the range, note Table 220.55 Column C gives 8 kW for a single range of 8–12 kW — you don't use the full nameplate. Dryers use the larger of nameplate or 5,000 VA (220.54).

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