did a search on reddit and found this test 4770k and crossfire 290s. Idle around 80 watts and high CPU loads will put it up to around 140. When I tested it running Crysis 3 it was at around 670 watts.since we're only talking about CPU mining, the overall PC power consumption will be, by my estimates, less than 25% more than what it's currently at :D

if power consumption is a real problem .... well, i can suggest mining on the Low setting, that will barely use any resources <3 and compensate your low mining power on the referral part ;) their system has 10 levels deep rewards ... the math behind it is just awesome :P