I am NOT a gamer and I use my gpu for calculation ONCE A WHILE. I hate to let the GPU sits there doing nothing and wasting 15 watt of electricity for nothing. Can I add a toggle switch on ONE of the wires on GPU external power PCIE cable so that I could to turn GPU on or off? There are three 12V pins/wires. Can I just add ONE switch on one of the wires ? If yes, which 12V wire? Or I must put 3 switches on THREE 12V wires? Thanks for any info.