Hair dryers: the common maximum wattage available in the US is 1875. This is mostly a resistive load with a small fan motor. If an audio amplifier were a pure regulator of power merely dispensing power as needed at 100% efficiency and presenting a purely resistive load, we could then reach just over 7 x 265 watts (RMS) of continuous power from a common 15A circuit in the USA or Canada.

Wikipedia articles on alternating current and electric power tell us that the peak voltage available from a 120 volt AC outlet is almost 170 volts and that the apparent power can exceed the real power if reactive power is a part of the equation. As our amplifiers employ sizable transformers and capacitors, reactive power is definitely a part of the equation. (More information here .)

Then there is the test article at the Audioholics site. If many of the manufacturers are using this test, where ‘continuous’ is not ‘continuous’, then it does make sense in a competitive environment to subject one’s own amplifier channels to a truly continuous test and put those numbers before the buying public when other manufacturers use the much less strenuous test? The interested consumer will perhaps read reviews that included bench testing and thereby some differences in amplification will be revealed. But the average buyer who frequents the larger chain stores and makes decisions on popularity of brand, looks, and specs printed next to the price may not readily understand why an Outlaw amplifier rated for 125 WPC might outperform the amplifier section of a receiver rated at 170WPC.

Bottom line: determining delivered power from an amplifier is not a simple matter of multiplying volts and amps. Measuring this power is possible through some mildly complex analysis of volts and amps delivered by the available channels, or by such means as equivalent energy delivered into a thermal system – if the power output of your amplifier would heat a liter of water as fast as a 100-watt plain resistive load would, then that amplifier is delivering an average of 100 watts over the same period of time, much longer than the above mentioned test.

By the way, I’d be more concerned with the thermal aspects than the power specifications. Who among us would expect to deliver 200 or 300 watts continuously to our loudspeakers and expect them to survive? Think of it this way (don’t do this, just imagine, OK?): take a spare loudspeaker enclosure, physically (not electrically) attach two 100-watt light bulbs to the woofer, seal the enclosure, then apply power to the lamps. How long until you smell smoke, or worse? Can you say “Easy Bake Oven” (which uses a 100 watt lamp maximum)? My loudspeakers are rated to 300 watts, but I wouldn’t expect them to remain unharmed if subjected to a continuous long-term average dissipation exceeding about 30 watts.

As long as my 770 amplifier can take my speakers cleanly through peaks exceeding 300 watts, I’m not concerned with using the amplifier output to turn my speakers into musically modulated heat sources (which they are, but on a small scale) for continuous 200+ watt duty.