does amp draw alot of power when volume is zero

Agree the best simple way to know if your stuff wastes power at idle is the see how much heat it puts out when idling. Nearly all the electricity used at idle is going into heat. The warmer the stuff is at idle, the more electricity you are using at idle.
My prior amp (forte 4a) was a small furnace at idle, and was just as hot idling all day as it was playing hard all day, Class "A".
My current amp, a Bryston 4B-SST2 has more surface and less apparent heat output per square inch, but it is much bigger and twice as heavy as the Forte.. so it is hard to say if it is more efficient?

For those who are actually curious, spend the 25$ on a 'kill a watt' power meter.

This meter will not only give you line voltage, but current, watts, VA AND therefore powerfactor.

A cheap test and part of my standard kit, though never left in system for long.

http://www.p3international.com/products/special/P4400/P4400-CE.html

Thanks for all the suggestions. Mine is a class D bel canto, fairly cool at idle, just a couple of warm spots but certainly not hot.

With a Class D amp; the output devices are turned off(no bias), until a signal is detected= high efficiency/low temps/low current draw at idle. Class A has full bias applied to outputs, ALL the time= low efficiency/lots of heat/high current draw at idle.

Agree with Magfan on the Kill A Watt; it has many other uses apart from audio.

Purchased mine at Radio Shack.