Antec Signature 650W Power Supply

Efficiency and PFC

Many people focus primarily on power supply efficiency when it comes to making a decision between the various offerings. High efficiency can save money in the long run, but you want to make sure that the highest efficiency matches the sort of load you will be running. Ideally, you also want the efficiency curve to stay near its maximum value for a large portion of the graphs; in particular, we like to see a steep slope at the start of the charts, indicating efficiency ramps up quickly even at lower loads.

Looking at the results for the Antec Signature 650W, a load of 100W only provides around 76-77% efficiency, which is really low for a modern power supply. If you are considering this particular power supply, your system should have a constant power draw of at least 150W and preferably 200W or more power to achieve maximum efficiency. The maximum efficiency of 87% with 230VAC is very good, as is the 85% efficiency with 120VAC. You'll probably want to avoid putting a load of over 500W on the power supply, however, as efficiency begins to drop at that point.

With lower input voltages, the power factor correction is very good. Even with the higher 230VAC input, PFC is still acceptable.