Okay, this gets more complicated, but when there's a power consumption number given it usually isn't at maximum power(unless it specifically said maximum). Usually for a receiver it's how much power is consumed with all channels operating at 1/8th of maximum. That may sound odd, but it's part of the Underwriters Laboratory requirement for testing for overheating. Example: 7x100 watt amps, 1/8th of that is about 90 watts, at 1/8th power this class of amp is roughly 20% efficient and would consume about 450 watts to output 90, and the 450 watt consumption figure might be on the back of the receiver.
