(After some flood event) I have two PCs each with 3 pieces of R9 280X (Gigabyte) taking 950 W as a whole while doing X11.
If calculating 50W for each PC parts (Mobo, CPU, ...) I arrive to 141 W of power per card.
Did you measure your cards to be 190W?
Or I have some bad config file here and not taking full advantage of the cards. I am hashing 2.1 X11 Mhs on each card. Are you doing maybe better?
My number includes all the "collateral" power usage and it is somewhat overstated / rounded up. I don't think you can exclude motherboard/CPU/cooling/etc from your expenses?
So here is what I'm getting: a four card rig pulls ~3 amps at 240V, approximately 720W. A box fan pulls another ~40W. Total 760W or 190W per card.
It's probably overstated by about 10W since my PDU shows between 2.8 and 3.0 amps and I'm just taking the higher value to be safe.
Hashrate is approximately 2.09 MH/ per card. There is a new version of sgminer floating around that is supposed to do much better, I'll try that next week.