Jake wrote:

The original question was about efficiency and not safety. UL ratings in the
US rate an appliance at X watts for the absolute possible worst case
scenario. Pf, service inductance, and other factors are used for when you're
trying to squeeze the most out of your energy dollar, or engineering new
equipment. When that nameplate goes on any appliance that's UL listed, rest
assured the current ratings displayed there are the absolute highest that
piece can possibly consume.

BTW, the National Electrical Code dictates that we must provide for that
nameplate rating... plus 20 percent... to make it safe.

I recall 25%. Where does the NEC mention 20%?

Would you have a chapter and verse?

Nick