When to use: Use this calculator when sizing the service entrance for a new or renovated residential dwelling. Per NEC Article 220, the service size must accommodate the total calculated demand load — not just the sum of all connected loads. Demand factors reduce the total because not all loads run simultaneously. Required for permit applications, utility coordination, and panel sizing.
This free NEC load calculator applies the National Electrical Code's Article 220 demand-load rules to size the electrical service for a dwelling. Enter the floor area, system voltage, and the major loads — small-appliance and laundry circuits, HVAC, water heater, dryer, range, EV charger, and other fixed appliances — and it returns the total calculated demand in volt-amperes, the calculated current in amps, and a recommended service-entrance size. It's built for electricians, electrical engineers, designers, and inspectors preparing service sizing for permits, panel selection, and utility coordination.
A service load is not the simple sum of every connected load — Article 220 lets you apply demand factors because loads rarely run at full capacity at the same time.
The standard (Part III) method builds the total like this: • General lighting and receptacle load: 3 VA per square foot of dwelling floor area (220.12). • Small-appliance branch circuits and the laundry circuit: 1,500 VA each (220.52) — at least two small-appliance circuits plus one laundry circuit. • A demand factor on the combined general lighting + small-appliance + laundry total (220.42): the first 3,000 VA at 100%, the portion from 3,001–120,000 VA at 35%, and the remainder at 25%. • Fixed appliances: four or more fastened-in-place appliances may be taken at 75% (220.53). • Electric range and cooking equipment: use the demand values of Table 220.55 instead of nameplate. • Electric clothes dryer: the larger of 5,000 VA or nameplate (220.54). • Heating or air-conditioning: include the larger of the two, since they don't run together (220.60).
Add those demand figures, then divide the total VA by the service voltage to get amps, and round up to the next standard service size.
Worked example: a 2,000 sq ft dwelling has a general lighting load of 6,000 VA (2,000 × 3). Add two small-appliance circuits and one laundry circuit (3 × 1,500 = 4,500 VA) for 10,500 VA. Apply 220.42: first 3,000 VA at 100% = 3,000, remaining 7,500 at 35% = 2,625, giving 5,625 VA. Add the range, dryer, water heater, and HVAC demand figures, total the VA, and divide by 240 V to find the service amps.
1. Enter the conditioned floor area in square feet and choose the system voltage (typically 240 V for residential). 2. Set the number of small-appliance circuits (two minimum) and toggle the laundry circuit on. 3. Enter the HVAC load in kW (use the larger of heating or cooling). 4. Fill in the fixed-appliance loads — water heater, dryer, range, dishwasher, EV charger, and any other fastened loads — in VA. 5. Read the calculated demand, the calculated current in amps, and the recommended service size; round to the next standard service (100, 150, 200, 320, or 400 A) and verify the result against your AHJ and utility.
Article 220 offers two ways to calculate a dwelling service. The standard method (Part III) itemizes each load and applies the individual demand factors above — it's the general approach and works for any occupancy.
The optional method (220.82) is available for a dwelling unit served by a single 120/240 V or 208Y/120 V set of 100 A or larger service conductors. It adds the general loads (lighting at 3 VA/sq ft, the small-appliance and laundry circuits, and the nameplate rating of fixed appliances) and applies 100% to the first 10 kVA and 40% to the remainder, then adds the heating or air-conditioning load at its own demand factor. The optional method is faster and usually yields a smaller service for an all-electric home; the standard method is more conservative. You may use whichever the code permits — they often give different service sizes.
Using NEC Article 220, add the general lighting load (3 VA/sq ft), the small-appliance and laundry circuits (1,500 VA each), and the demand figures for fixed appliances, range, dryer, and HVAC. Apply the demand factors of 220.42 and 220.53, total the volt-amperes, then divide by the service voltage to get the required amperes.
For dwelling units the general lighting and receptacle load is 3 VA per square foot of floor area (NEC 220.12), calculated from the outside dimensions of the dwelling and not including unfinished or unused spaces unless adaptable for future use.
The combined general lighting, small-appliance, and laundry load uses 220.42: 100% of the first 3,000 VA, 35% of 3,001–120,000 VA, and 25% above that. Four or more fixed appliances may be taken at 75% (220.53), the range uses Table 220.55, the dryer is the larger of 5,000 VA or nameplate (220.54), and only the larger of heating or A/C is included (220.60).
The standard method (220 Part III) itemizes each load and applies individual demand factors. The optional method (220.82), available for many dwellings served by 100 A or larger conductors, applies 100% to the first 10 kVA of general load and 40% to the remainder, plus a separate factor for HVAC. The optional method is quicker and often produces a smaller service.
Divide the total calculated demand in volt-amperes by the system voltage to get amperes, then select the next standard overcurrent device and service-entrance conductors that meet or exceed that value — commonly 100, 150, 200, 320, or 400 A for dwellings.
Yes — this is a completely free electrical load calculator that runs in your browser, with no download or subscription. Enter your building area, appliances, and HVAC, and it calculates the total connected load, applies the NEC Article 220 demand factors, and returns the required service amperage instantly.
Commercial electrical load calculations also follow NEC Article 220 but use different per-area lighting values (Table 220.12 by occupancy), apply receptacle demand factors (220.44), include the largest motor at 125% (220.50), and size feeders/panels to the calculated demand. Enter your loads here to total the connected VA and demand, then size the panel and service to the next standard rating above the result.
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