http://fastflip.googlelabs.com/view?q=view%3Apopular&a=sR7g3laAp2KgoM&source=news&type=embed
A friend sent me this link the other day. 131 lumens per watt LED. a T5 HO 4 foot bulb produces about 5000 lumen from 54 watts. these LEDs would only need 38 watts.
http://www.cree.com/press/press_detail.asp?i=1150834953712