I just checked:
Section 220.53, part of the standard calculation, mentions the use of nameplate ratings for the appliance loads (which includes water heaters).
Sections 220.82 and above, part of the optional calculations, mentions the use of nameplate ratings as well.
So for hot water heaters, are we allowed to use the adjusted wattage, at 75%, if we use a 240 rated appliance on a 208 volt panel? Both standard and optional calculations mention 'nameplate'.
Funny, my dryer question morphed into water heaters