2.72 MH/W 2300 MH/S @ 845W (at the wall, dedicated 240V circuit).
2.65 MH/W 2300 MH/S @ 870W (same system on 120V circuit)
5x7970
filesys: wd green 500g win7 diablo
voltage: 1.056
clocks: 1049/685
killwatt: 1160
Mh: 3120
2.69 MH/W
Dat. how did you measure this on the 240v, i have my 79xx on 220 now, but cannot measure the watts directly
TADA ....

Well I measured amps & volts. Remember the two legs of 240V circuit in US wiring are out of phase so to read current you need to clamp just one conductor.
They make adapters like this:
http://www.service.kleintools.com/Marketing/Catalog_Imagery/69400_ICON.JPGbut I have the rigs connected to a PDU using C14 to C13 cables and I doubt anyone makes an adapter so I modified one power cable which I use for testing only.