The ASICMINER source says 4.2 Joule/Ghash:
https://bitcointalk.org/index.php?topic=91173.msg1215501#msg1215501

(BTW, fix your units, it's either Watt/Ghash/s or Joule/Ghash Tongue

)

I've fixed the OP. I'm still debating whether or not to put the bASIC claims from the BFL thread in the OP. Anyone have an opinion on this?

Do it and add a disclaimer on those figures until we get the correct/real numbers.