If you’re like the average user, you rarely give your PC’s power supply unit (PSU) a second thought. It doesn’t matter whether you’re buying a name-brand computer or the $600 special from your local computer supplier, only high-end gaming enthusiasts are likely to give the PSU a second thought.

And in most cases, you shouldn’t have to. Even the $AUD40 case from my “local” now comes with a 500-watt PSU and for most applications, it’s more than enough.

There is some spectacularly bad advice going around on the web at the moment. I recently read at one site that the average computer draws 250-watts of power and that you needed some special widget to drop it down.

If you have a 19-inch widescreen or even a 22-inch widescreen LCD with a typical Core 2 Duo-class desktop PC, you’re looking at around 130-watts of power being consumed in standard applications.

So if that’s the case, why is there such a thing as a PSU after-market in the first place? Well, the key is that the typical cheap PSU is fine for standard applications but if you’re thinking about upgrading your PC’s graphics cards to something with a bit more “heat”, that’s when you may need to start thinking about a new PSU.

And this is where most people start getting into trouble – they don’t think about the PSU and just start throwing in faster and faster graphics cards until either the PC starts crashing or the PSU gives up its quota of blue smoke.

If you’re going to upgrade your graphics card, make sure your PSU has sufficient capacity to handle it. Just to give you an idea, a graphics card running Crysis can triple the power consumption of a PC. A GeForce GTX 260/280 card inside a Core 2 Duo E8500 PC will chew up as much as 300-watts of power (not including the monitor). That’s what I’ve measured in PC User Labs and also at home.

The thing though is that even those “as much as” results are average readings. Instantaneous peaks can be higher again and your PSU has to have the reserves to handle it.

My rule of thumb is that you need to have a PSU with double the required capacity so if the PC is pulling 300Watts, a 600-watt PSU should be inside it. Now of course, not everyone has their own power meter to measure power consumption but the graphics card vendors do provide their own rule of thumb on the minimum requirement to run their cards.

PSU recommendations

Darren Yates