We used the same dual-platform system from previous 600W-700W power supply reviews to stress the Cooler Master iGreen Power 500W. That might not sound fair, but we were always capable of removing components to drop the load if needed.

Transitional load occurs when a part of the system that's normally idle powers up, such as when burning a CD or starting a game. In support forums, the common question "Why does my system lock up or restart whenever I run [insert power-hungry process]" can often be explained by the power supply not having enough stability across one of its rails to support the sudden increase in load -- causing a brief drop in line voltage. To test this, we hot-plug and remove four previously retired WD31600 hard drives, for a combined 50W startup load.

Rated at 526W peak draw, our test system exceeds the iGreen Power 500W continuous output rating and proves its ability to operate under extreme conditions. Because we were already beyond rated capacity, we listed the minimum voltage under 50W added transitional load separately from the minimum voltage from normal use.

Voltage stability proved impressive, with our overloaded configuration causing 2 percent maximum fluctuation in the 12v rails. The smart fan screamed in protest (estimated in the high 40dB range), but even after two hours of running beyond rated capacity we were unable to cause a thermal overload.