[GTALUG] Intel i7-6700 vs Xeon E3-1230 v5 --> 65W vs 80W ??

Intel i7-6700 and Xeon E3-1230 v5 are pretty much the same, except that i7 has builtin Graphics and Xeon does not.  I don't get it.  How can i7 with builtin graphics consume less power?-- William