Standard Method vs Optional Method for residential load calculations

[Carultch]

The optional method (first 10 kVA of general load + 40% of remaining general load + HVAC load) is a much simpler calculation, and it often yields much smaller results for service size calculations.

I'd like to ask, what then is the purpose of the standard method? A more complicated calculation that often yields more conservative results. I would think that a more complicated calculation should be the more ambitious, rather than the more conservative.

Is it simply an academic exercise for taking an exam, of the way we used to do the calculation?
Am I supposed to brute force both methods, and pick the larger of the two?
Or is it conditional on when the optional method can apply? And in such an instance, there is no purpose to the standard method.

 

[Dennis Alwon]

I don't have an answer but I believe before the 2005 NEC there were requirements to use this method. One req. again I think, was for the home to be all electric. Not sure why it all changed

 

[Smart $]

Can't answer your question specifically, but I think most tend to overlook the fact the connected load must exceed 100A before you can even use the optional method... another play on the load diversity of households.

 

[augie47]

Note that with the standard method you are given data for a number of loads whereas with the optional you need nameplate data. Seemingly the "standard" is designed more for unknown loads where the optional lets you take advantage of the actual load.