The new 8 CPU core Power Mac is capable of drawing over half a kilowatt under heavy load according to xlr8yourmac.com.
Power Fractal: 562 - 584 watts
Half. A. Kilowatt.
Crazy. That's almost 10 60 watt light bulbs.
I've gotten over $200 in cash back from them at places I would have shopped anyway! Ebay, Staples, more! I put it at the top because they ROCK. Basically, you get a kickback from Ebates when buy.com or whoever pays them. Win-win. If you like throwing money away, don't use them!