You don't have to run it at that power level. If you use the Quiet mode in the firmware, you'll get a max voltage for the ASICs of 642 mV instead of 750 mV. I would guess that would reduce your J/GH by a factor of about (642^2 / 750^2) = 0.73 to about 0.47 J/GH, and reduce performance by a factor of about 642./750 = 0.856 to around 3.8 TH/s at 1900 W.
Nice idea, but dropping the machine all the way down to 3.8 TH/s will massively hurt profitability. Which is why Spondoolies' $/GH current compensation plan is inadequate.