Load Calcs with multiple Sub Panels

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Solar Noob

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Location
California
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Electrical Engineering (in training)
Hi everyone I have another dumb question about load calcs, this time if you have multiple sub panels.

When doing load calcs, are the subpanel loads supposed to be calculated separately or should the subpanel breakers in the MSP be rated at 125%?

The panel I am working with is a 200A buss rating, and there is a 100A sub panel breaker and a 60A subpanel, which has EV attached to it. I have pictures of the loads in all three panels, but I am not sure if I am complying with NEC 705.12 while attempting to do the load calculations from NEC 220.87. Do the subpanels need to be rated at 125% due to the 705.12 saying service panels can't go over that amount, simplifying the calculation part on my end, or do those loads need to be calculated separately? Any help on clearing this up is welcome.
 
What a confusing way to ask the question. Why are you doing load calcs in the first place?

If you are trying to determine if the main breaker can be downsized to comply with 705, you do a load calc for all the loads in the home. How they are divided into subpanels is irrelevant to that.

If for some reason you're doing a calc for an individual subpanel breaker or feeder, you only consider the loads supplied by that breaker or feeder. You cannot normally use 220.87 for that.

705 doesn’t contain any type of 125% requirement for service panels. 705 doesn’t change the way you do any load calcs. You do not do load calcs to comply with 705. You do them to check that your ideas for complying with 705 (e.g. downsizing a main breaker) don't violate 220.
 
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