xbitlabs measured the power consumption of the new revision of the Athlon 64 chips and found them actually higher (but only slightly).
Here is the relevant page in the xbitlabs article.
Here is another choice quote from the article:
"All this pushes us towards the conclusion that AMD didn’t focus on lowering the power consumption and heat dissipation of its new Venice based processors"
Power consumption of Rev. E Athlon 64
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