RMS Power?

Faulty term watts rms or rms power came most likely from around 1975 FTC standard for power rating. FTC realized, that they goofed up and 25 years later in 2000 they corrected it .

http://www.n4lcd.com/RMS.pdf

I think Roy Lewallen explained it very well:
http://eznec.com/Amateur/RMS_Power.pdf
In his summary:

The equivalent heating power of a waveform is the average power.
The RMS power is different than the average power, and therefore isn’t the equivalent heating power. In fact, the RMS value of the power doesn’t represent anything useful.
The RMS values of voltage and current are useful because they can be used to calculate the average power.

Thank you roxy54.  Almarg is much better in explaining technical merits. I'm just trying to contribute something being grateful for all things I learn here.  

imhififan, Thank you for posting.  Example of the wrong average power calculation in the second article is very interesting.  Using averaged values of voltage and current produced error of 50%.  It is very common error.  People who design test and measurement equipment (often big companies) make this mistake all the time.  For instance, when calculating mechanical power, they take average (filtered) values of speed and torque and multiply them, instead of taking instantaneous values of both, multiply and average (filter) the product - mechanical power.  For constant torque and speed it does not make a difference, but as soon as oscillatory component appears error becomes significant.  Even single percent error is very important for efficiency calculation.  Of course it has nothing to do with audio, but shows that "Power" is a muddy subject.

Thanks for the nice words, Kijanki. But you’ve explained it well, IMO, as did the summary quoted above by Imhififan. And I of course agree with your point.

As you indicated, the references to RMS power or watts RMS that are often seen are actually references to average power, which are calculated as the product (multiplication) of RMS voltage and RMS current (assuming voltage and current are in phase with each other). And as you and the reference provided by Imhififan both said, RMS power is certainly something that can be calculated for a given power waveform, but it would be a different number than average power, and it would be a quantity that has no relevance or usefulness. While average power, being proportional to heat generation, is relevant and useful.

Widespread usage of incorrect terminology doesn’t make it correct. Just as widespread misuse of the English language doesn’t make it correct. For example, many people would say that they could care less about this topic, even though that is the opposite of what they mean :-)

Best regards,
-- Al