So I have been very interested in finding out exactly how much extra power my rig draws while mining. I have a quad core AMD that I had originally been using as a Samba server for the family. Since this had 2 PCI-E slots open, I put in a pair of Sapphire Radeon 5850, a new power supply, installed Ubuntu 10.10 and set off to mining.
So I got an inductive ammeter and a special plug to measure the AMPS with my rig running. Here is what I got;
No load (Radeons not mining): 2.2 Amps or 242W
Half Load (1 Radeon mining): 3.5 Amps or 385W
Full Load (2 Radeons mining: 5.0 Amps or 550W
So basically if I have my math is correct my delta is 308W extra, as the thing would be running 24X7 anyhow. With .15kWh for electricity, that's about 33.75 per month.
My extra hardware for mining included the 2 5850's, 1 power supply and 4 extra fans. Total is about $440. I am getting 340Mhash/sec with each card for a total of 680 Mhash/sec. I made my money back in about 2 ½ weeks.
My Radeons also run at about 70C - 72C while mining.
Here are some pictures of the measurements and my rig;http://i1184.photobucket.com/albums/z327/Bruce_Lee2/1.jpghttp://i1184.photobucket.com/albums/z327/Bruce_Lee2/2.jpghttp://i1184.photobucket.com/albums/z327/Bruce_Lee2/3.jpg