Electrical
NEC Load Calculator
Size a residential service per NEC Article 220. Standard, optional (220.82), and existing dwelling (220.83) methods with demand factors for general lighting, cooking, dryers, fixed appliances, HVAC, EV chargers, and motors applied automatically.
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Property
Calculation method
Standard method (NEC 220 Part III)More tedious
Itemize every load that will be on the service. Each demand factor (general lighting, cooking, dryers, fixed appliances, HVAC, motor) applies separately per its own NEC table. Skip nothing: leaving out a real load undersizes the service.
When to use: new construction, or any time the AHJ asks for the "long-form" calculation. Always defensible, never wrong to pick this.
Switch to Optional (220.82) when sizing a NEW service for a one-family dwelling, or to Existing (220.83) when adding solar, storage, a heat pump, or an EV charger to an existing service. Both are faster and typically give a 10-15% smaller answer.
Cooking equipment NEC 220.55
Ranges, ovens, cooktops. Demand factor by count.
Subtotal: 12,000 VA
Electric dryers NEC 220.54
5000 VA minimum per dryer. Demand factor by count.
Subtotal: 5,000 VA
Fixed appliances NEC 220.53
Water heater, dishwasher, disposal, hardwired microwave, washer, hot tub, pool pump, etc. 75% demand factor when 4 or more.
Subtotal: 6,600 VA
HVAC heating NEC 220.60
Furnaces, heat pumps (heating side, compressor plus any backup strips), electric resistance heat. Larger of total heating vs total cooling counts.
HVAC cooling NEC 220.60
AC units, heat pumps (cooling side, same compressor). A heat pump is ONE unit: list it on both sides at its real draw and 220.60 keeps only the larger, it is never counted twice.
Subtotal: 4,800 VA
Other (continuous) loads NEC 230.42(A) / 625.41 / 220.57
EV chargers, pool heaters, and other continuous loads. Standard and Optional methods apply 125% per NEC 230.42(A) and 625.41. The Existing method (220.83) takes these at nameplate: enter EV chargers at nameplate or 7,200 VA, whichever is larger, per NEC 220.57.
Subtotal: 7,200 VA
Enter VA of the largest motor on the service (typically the AC compressor or pool pump). The 25% adder is applied in addition to the motor's own VA, which should already be listed in HVAC, Fixed, or Other above.
Recommended service
175
A AutoCalculated load: 165.0 A at 240 V (Standard method)
Tight headroom
Using 94% of a 175 A service. Future loads (battery, second EV) would push past 100%.
Service conductor NEC 310.12
About this calculator
NEC-compliant. Free to use. No watermarks.
Load calculations are how you size a service. Get them wrong and you either oversize the panel (wasted money) or undersize it (a violation, and the AHJ rejects the permit).
This calculator runs three NEC Article 220 methods. The standard method (Part III): 3 VA per square foot for general lighting, 1500 VA per small-appliance and laundry circuit, the Table 220.42 demand factor on general loads, Table 220.55 for cooking, Table 220.54 for dryers, the 220.53 75% rule for four or more fixed appliances, the larger of heating vs cooling per 220.60, and a 25% adder on the largest motor per 220.50. The optional method (220.82): first 10 kVA at 100%, remainder at 40%. The existing dwelling method (220.83): first 8 kVA at 100%, remainder at 40%, the code path for adding solar, storage, a heat pump, or an EV charger to an existing service without an upgrade.
Homeowner checking whether an EV charger fits your panel? Use the plain-language EV charger load calculator, which runs the same 220.83 engine with typical appliance values filled in for you.
NEC references
- NEC Article 220, Part III: Feeder and Service Load Calculations
- NEC Article 220.82: Optional Method for Dwelling Units
- NEC Article 220.83: Existing Dwelling Unit Calculations
- NEC Article 220.57: EVSE Load (7,200 VA minimum)
- NEC Table 220.55: Demand Factors for Household Electric Cooking Appliances
The same calculations, running live as you design.
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