Here are the power number comparing the 2700K to the 4770K. Both are very similar and basic systems.
2700K
850W power supply
Intel SSD
2 x 4GB 1600 Memory
DVD
Intel DZ68BC motherboard
OpenSuse 13.1
HT off
4 Cores
Turbo disabled
4770K
610W power supply
Intel SSD
2 x 4 1600 Memory
DVD
Asus Z87-Expert motherboard
Windows 8
HT off
4 Cores
Turbo disabled
Code:
Idle SOB TT small TT blend TT large OGR RC5
2700k 42 129 124 122 129 104 104
4770K 66 142 142 129 140 97 95
Take away: 4770K with avx2 is faster but requires more power to do it(nothing for free). I suspect the extra power is the stress on the memory system due to the increased throughput. FFM3 instructions use more power than AVX. Makes sense given the larger registers.
99% sure the difference in idle power has to do with the c-states in the bios. I believe they are disabled on the 4770K(something we normally do for testing) but enabled on the 2700K after the last bios update. This would not affect the power usage under load.