Yes, all agreed, but the shape of the mains waveform is
immaterial, unless you are talking a purely resistive
load like a light bulb. The point that I have been trying
to make all along is that when you are trying to measure
power, it's a function of both voltage and current draw,
and in the case of a SMPS, especially one that's in
standby mode, the current draw from the mains supply
voltage, is very likely to be anything *but* sinusoidal.

Arfa
It's also likely not to be a simple product of the RMS
current drawn & the RMS voltage of the supply, as the
input circuitry contains reactive and regulatory elements
that alter the phase relationships between the current &
the voltage in a manner that can't necessarily be
predicted easily.
(snip)
Tciao for Now!

John.

This all started with a discussion of the Kill-A-Watt meter
which measures RMS voltage, RMS current, and Watts. Maybe
the following will clear some of the confusion.
The computation of RMS was described in an earlier post. The
product of RMS voltage and RMS current is Volt-Amps. Power,
and therefore power consumption (Watts=power/second), is
computed by the integration of the product of instantaneous
volts and amps over time. The power factor then becomes
Watts/Volt-Amps. The accuracy of the wattage and RMS
calculations with voltage or current waveforms that change
rapidly is related to the sampling rate used in the
integration. Any wave shape for either voltage or current
will produce mathematically meaningful RMS and power
measurements. I am sure someone will point out any mistakes
I have made here.

David