Here's a list of the threads we have which have a piece of marine hardware benchmarked on it's various settings to provide real world indication of the watts our equipment consumes.
Manufacturers exaggerate the "Watts" spec of lighting, as people percieve that to mean brighter lights, and might understate the power consumption of things like powerheads, where more efficient units are obviously more desirable.
Also, manufacturers usually only specify a maximum power draw, but our hardware, ozone generators, powerheads, wavemakers (which are intermittent!) and lighting isn't always used on their max settings. So where possible, we have taken readings from equipment's various output settings.