Useful PSU Calculator

I found this handy website that helps calulate roughly how much power a PC uses based on the components it uses.

http://extreme.outervision.com/PSUEngine

I started looking at this when my wireless keyboard was becoming unresponsive in CoH (even with fully recharged batteries in). I thought that the usb receiver may not have been getting enough power... fortunately, according to this site, my PC setup only requires a minimum of 440w (I currently have a 650w PSU).

This utility caters for SLI/Crossfire, multiple fans, CPU overclocking, and many other features, and I think could be useful for a lot of CoH players with custom builds, or who are looking at new custom builds

That one's surprisingly accurate. It estimated my computer's peak power consumption at 293 watts and recommended a 350-watt PSU; my measured peak consumption is 224 watts and I'm running on a 430-watt PSU with no problems.

Most calculators grossly overestimate power consumption, recommending either a 550-watt or 650-watt PSU for my system.

Assuming your measurement is at the wall socket, which is AC watts, you are using even less depending on the efficiency of your PSU. With an 80% efficient PSU your computer is actually only using 180 DC watts, an 85% efficient PSU then 190 DC watts. Power supplies are rated at DC watts.

Bear in mind the efficiency rating is given at a certain percentage load - usually 50% - if you are running at 100% of rated load the efficiency will usually be significantly less.

Not true with 80plus rated PSUs. Efficiency is measured at 20%, 50% and 100% rated load and all three must be at or above to qualify.

Generic 80plus certification is 80% at those three points.
80plus Bronze is 82%/85%/82%
80plus Silver is 85%/88%/85%
80plus Gold is 87%/90%/87%
80plus Platinum is 90%/92%/89%

An 80plus sticker, assuming it's real (not always the case sadly) at least means that X watt PSU can actually deliver up to X watts.