Efficiency
While performance is the primary issue with a power supply, efficiency is also very important. When demand for power is rising, the efficiency of the test devices becomes particularly significant, so we rate efficiency even more highly on high-capacity units.
Why is it so important? First, because it represents energy cost savings. At an output of 600 watts, a power supply running at 80% efficiency would sap a whopping 750 watts from the network. At an efficiency rating of just 60%, the same output would eat up a kilowatt from the grid!
Besides the savings in electricity, there are other aspects to consider. The most notable is that the power that is not used to drive components is converted to heat by the circuitry. Thus, the lower the efficiency, the more waste heat the device produces, which in turn, translates into a raised need for cooling. Good cooling is only achieved with larger and faster fans, so a power supply with low efficiency is generally louder than one with high efficiency.
Efficiency can also affect the supply's useful life, too: the warmer the components get, the shorter their lifespan. This point is not necessarily a determining reason for buying a highly efficient power supply, but all things considered, it makes it a far more attractive purchase.
Leads And Plugs
Even when you've got performance and efficiency, that's not everything. There are many power-hungry components in a PC, and whether they actually get their energy when they need it depends on the number and length of plugs and leads available. After all, a power supply with 600 efficient watts is worth little if there are only four 5.25" connectors to distribute the power!
A 24-pin plug for ATX output is used in the new ATX12V 2.01 specification. Users with older mainboards using 20-pin ports will be interested in the matter of divisible connectors that can be cut down to 20 pins, and the availability of adapters. Thus, we also assess these issues in our evaluation.
