With GPU's gobbling power at unheard rates, it's important to choose your power supply carefully. You may save a few dollars on a bargain power supply but usually in the end, you pay more on the electric bill than you saved. It makes sense opt for a high quality, high performing power supply that might cost a few dollars more but shaves a few bucks off the electric bill each month. At low draw conditions, the OCZ Z 850W power supply hits about 81% efficiency but as load increases it becomes more efficient hittings as high as 91 - 92% efficiency.



Link: Bjorn3D