NVIDIA has fixed the nvidia-smi.exe tool in the latest driver update. (driver 6/22/2015 version: 353.30)
It's awesome but far from perfect.
I don't trust software reported power consumption figures (with good reason) so I looked into it.
My same 970 jumps from between 130W and 205W in nvidia-smi (180W at the wall) on stock even in benchmark mode doing quark and for 750 Ti's it shows incorrect max (cap) figures.
It shows 46, 38, 45 watt figures for stock Gigabyte, Asus, MSI cards while each rig consumes about 405 watts, 70 watt being the idle power consumption of the rig so it comes down to 55.8W per card without the rig (for quark).
Here's an unmodified BIOS just pulled from an Asus card (GTX750TI-PH-2GD5):
It suggests that the nvidia-smi figures are based on the 38.5 value while that's not how much these cards can pull.
Mining groestl the rig consumes 457 watts which comes down to 64.5W per card but nvidia-smi figures are based off of the 38.5W number and it throws the card reported TDP% number (~95%) at it so it shows 37/38W and 38/38W.
With that said, my numbers are with measured numbers from the wall are:
750 Ti 5630 kh/s - 55.8W - 100.8 kh/w;
970 15300 kh/s - 180W - 85 kh/w.
. More can be read in the VTC thread. 
