NEC 2026

Existing Home Load Calculator

Check whether an existing home's service can take a new EV charger, heat pump or range, with each rule and clause shown. The result updates as you type.

Updated

Service
House (120.83(1) and (2))
Existing equipment, nameplate VA (120.83(3))
Heating and cooling (the larger one counts)
New loads to add (Table 120.83)

Enter the floor area to see the load on the service.

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For reference only. Always verify with the NEC edition adopted by your AHJ.

What this calculator covers

It applies to an existing dwelling unit served by a 120/240 V or 208Y/120 V, 3-wire service, and answers one question: can the existing service take additional loads such as an EV charger, a heat pump or a new range? It is not for a new home, a multifamily building or a service of any other type.

In the NEC 2026 this method is section 120.83. In the 2023 NEC this calculation was 220.83, and the general lighting figure differs between the two editions, so a hand calculation from the older edition will not match. The calculator uses the NEC 2026 numbering and values throughout.

How the existing-home load is counted

  • General lighting and receptacles (120.83(1)): 2 VA for each square foot of floor area.
  • Small-appliance and laundry circuits (120.83(2)): 1500 VA for each circuit.
  • Nameplate equipment (120.83(3)): fastened-in-place appliances, ranges and ovens, dryers, water heaters and EVSEs on their own circuits.
  • Heating or cooling: the larger of the two, never both. The smaller one is listed as not counted.

Table 120.83 then sets the percentages. The first 8 kVA of existing and new load counts in full. Above that, the remainder of the existing load counts at 40 percent, a new EV charger at 80 percent and other new loads at 50 percent (new electric resistance heating also uses its own Table 120.83 percentage). The total in volt-amperes is divided by the service voltage and compared with the service rating.

The result shows each line with its rule, so you can check it by hand. For conductor and breaker sizing after you know the load, use the wire size calculator.

Existing-home load questions

What is NEC 120.83 used for?
It checks whether an existing dwelling's 120/240 V or 208Y/120 V, 3-wire service can take additional loads, such as an EV charger, a heat pump or a range, using the percentages in Table 120.83. The first 8 kVA of existing and new load counts at 100 percent and the rest at the table percentages.
Is this 220.83 or 120.83?
Both names refer to the same existing-dwelling method. In the 2023 NEC this calculation was 220.83; in the NEC 2026 it is 120.83. This page uses the NEC 2026 numbering and values.
Can I add an EV charger to a 100 amp service?
No, for the example house: a 2,000 ft² house with a range, dryer, water heater, dishwasher and air conditioning on a 100 A service is at 77.83 A before a charger. A 48 A charger takes it to 116.23 A, which is over the 100 A rating. The largest charger tried that still fits is 24 A (97.03 A in total). Enter your own house above: the answer moves a lot with the range, dryer and heating.
How is an EV charger counted?
A new EVSE is counted at 80 percent of its rating in Table 120.83, after the first 8 kVA allowance has been used up. Other new loads, such as a new heat pump or water heater, are counted at 50 percent, and the remainder of the existing load at 40 percent. Enter the charger as a new load of type EV charger, in volt-amperes (amps times volts).
Which loads does the calculation include?
General lighting and general-use receptacles at 2 VA per square foot (120.83(1)), 1500 VA for each small-appliance and laundry branch circuit (120.83(2)), the nameplate rating of fastened-in-place appliances, ranges, ovens, cooktops, dryers and water heaters that are not on those circuits (120.83(3)), and the larger of air conditioning or space heating. Add each appliance in the existing equipment list.
Do heating and air conditioning both count?
No. 120.83 uses the larger connected load of air conditioning or space heating, but not both. The calculator counts the larger one and lists the other with its VA but marked as not counted, so you can see it was left out on purpose. When both are equal the heating is counted.
What if the result is over my service rating?
Then the service cannot take the new load as entered. The two usual answers are a service upgrade, or load management. This calculator does not model energy management systems; the Code covers power control systems in 120.7 and energy management systems in Article 130, and an installer or AHJ decides whether that route is available. When a larger service is suggested, the sizes come from a list of common residential ratings. Common residential service sizes, not an NEC requirement; your utility and AHJ decide.
What does this calculator not cover?
It takes one heating figure and one cooling figure, so if a new unit replaces an old one, enter only the unit that will remain. It does not cover new dwellings, multi-family buildings, services other than the two listed, or local amendments. Always check the result against the edition your AHJ enforces.

You can read the NEC 2026 for free at NFPA free access.