Building an Energy Efficient, Always-On PC?

An anonymous reader asks: "Like many readers, I find it necessary to leave my home PC running 24/7, for things like web or FTP servers, BitTorrent, or simply to make sure I don't miss any messages on IRC or my instant messaging client. It has been about 3 years since I built my current PC, and keeping it running all the time uses a lot of juice. With my next PC, I would like to do what I can to keep the power-consumption to a minimum, without sacrificing processing power or other features. What should I look for when choosing components for my PC, and what other ways are there to keep the power consumption down?"

Re:Not one... two.

[PipOC]

A C7 would likely be a much better choice for a webserver, you get SATA, and a much faster processor, which is much more suited to serving web traffic. And if you're hosting torrent files you will likely be having lots of disk access, making SATA a huge benefit.

Re:Dont bother.

[daeg]

It also depends on how the power is used. If it's being used in the CPU, it's going to kick out a lot of heat, which can't be ignored, either, although can be hard to quantify. If your system is using less power, it's also probably kicking off less heat. If you're in Florida like me, you should pay attention to that, considering most Floridians air condition for 10-11 months out of the year.

Re:Don't forget the monitor

[compwizrd]

Oops, that 150W includes the P4 2.4ghz w/2 HD's and a gig ram of ram that is attached to the UPS as well.