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Load Testing

Another major problem with almost all PSU reviews around is the use of an inadequate load.

Some websites will use a regular PC on their PSU review. The problem is that high-end power supplies nowadays can deliver at least 600 W and a regular PC is not able to pull all this power. Even if you use a very high-end PC with two CPUs, several hard disk drives and even four video cards, you won’t be able to say how much power you are pulling at a given moment and you also won’t be able to say up to how much power you were able to pull from the power supply, since you are not using any measurement device.

The best example we can give on how this methodology is flawed is that website that gave a “Gold Award” to a 750 W power supply that burns if you try to pull more than 450 W from it.

Even if you are able to build a PC that can pull a significant amount of power from the power supply, you still have a few flaws. First, you don’t know how much power you are pulling from your system. Thus you can’t measure efficiency (efficiency is the relation between the amount of DC power that is being delivered to the computer and AC power that is being pulled from the power grid), even if you have a power meter connected to the power supply. Second, the amount of power a PC pulls from the power supply varies, even if you let the computer running the same program over and over. Third, you will evaluate a power supply under only one scenario: the amount your PC is pulling from it. With only one computer you can’t evaluate how the power supply will perform under several different scenarios. And this is imperative especially if you are willing to measure efficiency, because efficiency varies according to load.

Therefore the only correct way to evaluate power supplies is by connecting them to active load testers. You can see a list of websites that have this kind of equipment here.

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Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.