How can I measure power draw?

Thank you both for your responses. I have the published specs on all of my components.The thing is, I don't believe them.The P300 will give you a readout of power consumption of the components plugged into it. My Pass amp is supposed to draw 200 watts at idle, but if I run it and my front end stuff into the P300, the reading is about 190 watts. And then what is the P300 itself drawing from the wall? Some of the reviews of the PS Audio Power Plant P300 have stated that the unit draws 300 watts all the time, but PS Audio says this isn't true. So the reason for my question is to try to get a true measure of what's going on here. Bob, your solution is too tricky for me to attempt. I'll tell you, if someone could devise an in-line meter for this, I think it would be a useful addition to my audiophile toolkit. -Dan

Bob's solution is a good one, and not all that difficult. But, if you really want to know without any trouble, Allied Electronics sells a nice digital wattmeter, just plug in the equipment and read watts used. Regret to say the cheapest model is $450. Check ebay, etc. for used analog ones, listed as Variacs, Powerstats; they have all variable output voltage, a few have the wattmeter included. Rich

Drubin, Go to doubleed.com and check out their "wattsup" device. This unit plugs into the wall and then your amp plugs into this unit. Turn on the "Wattsup" and then turn on your amp. This unit measures the power consumption of your amp. It can also calcuate the cost of electricity. Pretty need stuff. I saw one at Fry's electronics for $80.00. Have fun.

The Wattsup sounds like just the ticket. I'll get one and report back. Thanks. -Dan

An accurate power draw cannot be obtained without considering the power factor. In essence this means measuring the phase angle of voltage vs current (as well as measuring voltage vs current). The true RMS power figure is obtained by: P = VI cos phi. The cosine of the phase angle is called the power factor. This formula holds for all sinewave sources of power (such as AC from the wall).