Uh, a lot. I haven't looked in a while, but probably 800-1000w

r730xd with 14 drives, dual procs and 512gb ram

r710 with 8 drives, dual procs and 144gb ram

r510 with 12 drives dual procs and 64gb ram

The heat generated on the back side is pretty high, so thats where my electric bill is going :(

My stuff only shuts down when the power goes out longer than my battery can hold