I was made to believe that it is your heaters and lights that consume the most power and filters and powerheads consume less than a lightbulb. My whole 55 setup and 10g QT uses less than 3 100W lightbulbs (258W).
This is interesting. At first I used to think the filters or heater were the worst power offenders....but it seems to be the lights, especially for those with planted tanks.
I found it useful when I was looking to choose a UPS for power backup. Since the lights and heaters are the biggest power hogs, if you only run the filter(s) in backup mode you can go quite a while.