Intology's got a good summary write-up of a study undertaken by an Austrailian consumer group about electricity consumption. If you've been leaving your PS3 on all the time, you apparently may want to reconsider.

"They found out that a medium sized refrigerator of about 12 cu. ft. volume (60 inches in height) will cost $50 a year while Sony Playstation 3 will cost $250 a year even if it is not in use and only turned on. Microsoft XBox came second behind Playstation 3."