Research: actual power usage modern PC's

Power consumption Stand-by and Hibernate

In the table you will find the comsumption of the PC's in both stand-by (S1 and S3) and hibernation mode. S1 mode is pretty simple, the average consumption is only a fraction less than when the PC is idling, so it will not make a massive impact on your energy bill come the end of the year.

Systems that are in the correct stand-by mode (S3) are usually pretty efficient, we measured and average consumption of around 8 Watt. So when you PC is on standby this will cost you around £ 6 a year, having a media centre PC and keeping it on S3 stand-by is not a lot worse than sitching it off completely.

Hibernation means that teh PC is powered down, but this doesn't mean it does not use any power. Our tests show that machines still use between 4 and 8 Watt when switched off, so if you want to ensure that the system is really off you will have to switch the PSU off or use a on/off switch on the power socket.

Important: efficient PSU!

One of the most important items in a PC is an efficient PSU, as this changes the 220-220V form the outlet into the 12V, 5V and 3,3V that the PC uses. As in all processes the PSU will lose some of the power, so the actual usage from the socket is always more than what the PC actually needs. The smaller this difference, the more efficient the PSU is. According to the official ATX specification a PSU should be at least 72% efficient, however this is not a very good score. If your system uses 200 Watt and your PSU is 72% efficient this means your PSU actualy needs 277 Watt to power it all.

All the PSU's that are taken up in our product database have the efficiency figures in the comparison tables. The recent tests we did showed efficiencies between 66.7% and 93%. The worst PSU therfore uses 398 Watt to power a 266 Watt system, the best one only 286 Watt. Quite a large difference and well worth considering when shopping for a PSU.

The most efficient and the worst PSU in our database at the time of writing this article.

A PSU will perfrom most efficiently when the system uses around half what the SU can deliver. This means that when you purchase a OSU you will need one that is double what your system actually needs. For instance when you are building a Core 2 Duo E6700 system as we have in this test that uses 220 Watt you should buy a PSU that can deliver a minium of 450 Watt.