New 2026 NEC Optional Calculation 120.83

[Elecbeej02]

Hello all! Hoping to get some clarification and opinion on the following regarding the residential optional calculation for existing dwellings 120.83

As I understand any heating and cooling load is to be calculated per 120.82(C) as also shown in the annex D examples. These loads are not included in the general load deration. Is this correct?

I understand that new EVSE can be added separately at 80% but how are existing EVSE loads to be calculated? 120.82(D) clearly states to add separately at 100% however EVSE is specifically listed in 120.83(3) along with the other general loads that are acceptable for deration. Which should be used?

Finally, 120.83 Table says “other new loads at 50%” here is my question. If my new load is a range, oven, water heater or dryer, because those appliances are specifically listed in 120.83(3) and included in the general derated loads are they calculated there, or am I overthinking and it’s as simple as if it is not a new EVSE, electric resistance space heating or heating and air conditioning it is added at 50%?

Thanks in advance

 

[wwhitney]

When reading 120.83, ignore everything in 120.82. So we have:

2026 120.82: General loads at 100% for the first 8 kVA, 40% for the rest, plus HVAC load at various specified factors, plus 100% of the EVSE load.

2026 120.83: All existing loads at 100% for the first 8 kVA, 40% for the rest (this includes EVSE and HVAC loads, although you get to omit the smaller of the heating or cooling), plus new EVSE and electric resistance space heating at 80%, plus all other new loads at 50%.

Cheers, Wayne

 

[Elecbeej02]

Hello, thank you for the response. I was originally thinking the same thing but after talking with several AHJ’s and after looking through the example calculation given in the NFPA link version of the 2026 NEC it shows a new AC load at 100% which is only referenced in 120.82.( I would include a picture of the example calculation but I’m not sure how to attach to this) I would assume that a calculation given as an example in the official NFPA Link app would be correct but maybe not. Seems to be several different interpretations of this around here
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[wwhitney]

Hello, thank you for the response. I was originally thinking the same thing but after talking with several AHJ’s and after looking through the example calculation given in the NFPA link version of the 2026 NEC it shows a new AC load at 100% which is only referenced in 120.82.

I don't see any examples in Appendix D that are for 120.83. If there are additional examples in NFPA Link which reference 120.83 and are as you describe, they are wrong. If you figure out how to post a picture, I would be interested in the details.

There's really no ambiguity here. If your calculation meets the predicates in the first sentence of 120.83, you simply apply 120.83 as written. 120.82 has nothing to do with such a calculation.

Cheers, Wayne

 

[tortuga]

If your trying to do real world calcs not just test prep getting 100% of the HVAC load (as a starting point) such as a heat-pump can get interesting, as Minimum Circuit Ampacity (MCA) is never 100% of the HVAC load. Manufacturers do not post single a 100% load on the sticker or data sheet (RLA Total) of a packaged heatpump.
To do a load calc I have to add up what the MFR gives; Compressor Running Load Amps (RLA) + Fan Full Load Amps (FLA) + other loads to get a 100% load number. If your doing a dwelling with one or two heat-pumps there is nothing wrong with using MCA your just adding extra (leaving amps on the table).