It also tells you how many watt hours are being saved using the site...
Blackle wrote:381,306.047 Watt hours saved
EDIT: It also has a free site promo tool to get your own site up and running.
EDIT #2: Found this from the Wikipedia article on Blackle...
Those lovely folks at Wikipedia wrote:The principle behind Blackle is based on the fact that the display of different colours consumes different amounts of energy on computer monitors .
The creators of Blackle cite a 2002 study from Roberson, who tested a
variety of CRT and LCD monitors and found that an all black screen
consumed less energy than an all white screen on all of them.
The creators of Blackle state that the idea behind the site came from a blog , which estimated that a black Google would save 750 megawatt-hours a year . On the Blackle homepage ,
the creators of Blackle provide a count of the number of watt-hours
that they claim the users of Blackle have collectively saved.
So all this begs a question: should we all have black backgrounds?
EDIT#3: Eep. A bit more research dragged this up:
What to think?
Apparently it uses more energy if you use smaller LCD monitors.
Meh, if you have a CRT and you want to give it a try, go for it.
Maybe I should have put this in Soapbox.