Anyone can tell me if there is a PSU that will only draw that much power from the wall outlet as much is being used by the computer at the moment? Or do all modern (80Plus) PSU-s do this? A friend of mine told me he’ll switch only for a PSU like that and that he saw one only but he forgot which one was it. Anyone heard about this?
All PSU’s only draw as much power as they need, regardless of model, design, age, etc. Efficiency determines how much power is wasted in the AC to DC conversion process.
Cool thanks, I was wondering about this but I wasn’t sure that it’s like this when my friend told me about this “special” PSU. Guess he just misinterpreted the text and got me confused too. Thanks.
The “80 Plus” certification means that with a load of between 20% and 100%, the PSU must be at least 80% efficient in the conversion process.
For example, let’s say all the PC components consume a total of 100 watts at a given moment. Assuming the PSU is 80% efficient when loaded at 100 watts, the PSU itself would consume 25 watts to make up the other 20%, resulting in 125 watts being drawn from the plug. I.e. 80% of 125 watts = 100 watts.
The 80 Plus comes in various levels also - Bronze, Silver and Gold. You’ll see a few PSUs with these certifications.
The minimum efficiency requirements for the certifications are as follows, going by the 80plus website:
[li]80 Plus - 80% efficient at 20% load, 80% efficient at 50% load and 80% efficient at 100% load[/li][li]80 Plus Bronze - 82% efficient at 20% load, 85% efficient at 50% load and 82% efficient at 100% load[/li][li]80 Plus Silver - 85% efficient at 20% load, 88% efficient at 50% load and 85% efficient at 100% load[/li][li]80 Plus Gold - 87% efficient at 20% load, 90% efficient at 50% load and 87% efficient at 100% load[/li][/ul]
If you have a few PSU brands and models handy that you’re not sure how efficient they are, you can look them up on the 80plus website list.
Unfortunately, as with other products, a more efficient PSU tends to be a lot more expensive than a less efficient model, so it’s worth taking into account how often the PC will run, especially continuously around the clock. Also note that a more efficient PSU does not necessarily mean it is more robust or reliable than a less efficient PSU.
Finally, when building a PC for energy efficiency, in my opinion, the parts that make up the PC (motherboard, CPU, HDD, etc.) play a more major part than the PSU efficiency. For example, there is no point in installing a high end graphics card if the person does not play games or use any CAD software, as a high end graphics card can easily consume over 50 watts alone idle.