In this Holiday Buyers Guide, we will be evaluating and recommending desktop PC power supply units. We should clarify that the selection of a PSU is based on parameters both objective (e.g. wattage, performance) and subjective (e.g. design, modular cables). That makes it very difficult to limit the selection of a PSU to just one per possible target class. We will be recommending at least two options for each market, based on objective parameters and our subjective opinion.

Before we get to the power supplies, we want to dispell a common misconception among users ? that a high wattage PSU will be better. That is not necessarily the case, because all switching PSUs are designed so as to deliver their maximum efficiency at about half-load (50% of their rated maximum capacity). Their performance will reduce not only at higher but at lower loads as well. As a matter of fact, the efficiency of any switching PSU typically plummets if the load is too low (usually below 15% of the units rated capacity). You should remember that the advertised performance of a PSU is within the nominal load range (20% to 100% of its rated capacity) and the manufacturer is not obliged to include information on how much the performance degrades at sub-20% load conditions. Therefore, the selection of a severely oversized PSU is both economically and practically senseless.