I'm not sure about the power consumption when triggered on but with a 0.0mV input, but the specs make the standby power consumption pretty clear:
Power Consumption: 600 watts maximum/<3 watts standby
You're looking at less than three watts per amp in standby mode. If I had to guess about the consumption when on with no signal, I'd say you're probably looking at 10 to 30 watts - that's just a guess, though, and Outlaw tech support may have a better answer for you.