Misleading Power Supply Ratings

Did you know that the supposed 420w Power Supply you are buying may not be a 420w power supply at all?


It’s unfortunate that some companies use PEAK POWER instead of CONTINUOUS POWER for the power rating displayed on the box.

Continuous Power and “Peak Power” are two very different standards, and unfortunately often misused. Continuous Power describes the real power a PSU can output continuously. This means that a PSU with 500 watts of Continuous Power can maintain stable, continuous output within the maximum load of 500 watts. A PSU with 500 watts of Peak Power, however, can only maintain such output for a few seconds.


Let’s look at Gigabyte’s PoweRock KX series, we’ll use the PoweRock KX420 as a study sample. Note that this is different from the PoweRock series (minus the KX) which is a pretty decent range of PSU.

In reference to the table below.


Take note of the last row on the table, it says “350W(Peak Power 420W)”. What it says is that the power supply is only capable of delivering 350W continuous power, the 420w is peak power that lasts only for a few seconds.

(I’ve no idea how it shows 350W there when total is actually 361W)

Why do they mark the power ratings as such? Marketing reasons.

So before you head out to buy a power supply unit – it’s best if you could check out the product pages, and perhaps even reviews of power supply units. They often provide good details on it. The product boxes aren’t always with the power distribution details.

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