I live in a temperate part of the country, hence none of that $120 came from running the heater or the air conditioner - at least not in the last couple of months. The majority of the power usage came from my computers - two desktops, one laptop, and two servers. Not only do these machines generate a ton of heat, they're apparently not too kind on my electric bill either.
As geeks go, this is a pretty mild setup. I've got a Vista gaming/dot.net development desktop, an ubuntu LAMP programming desktop, a laptop for the wife, a Win2k3 dot.net application/database server, and a fedora core LAMP/email server. I had two goals in mind - reduce the amount of hardware without reducing functionality, and make the hardware that's left run more efficient.
My configuration was in this state because I needed to isolate different islands of functionality more so than needing the horsepower that all these machines bring to bear. In fact, 99% of the time, these machines run at 2-3% CPU load anyways.
Step 1 - Virtualization
VMWare makes their server product available for free. What that allows you to do is to run multiple instances of different computers on a single physical box. I immediately installed this onto my gaming desktop and incorporated my LAMP development ubuntu machine as a virtual machine.
On the server side, I installed VMWare server on my Windows 2003 box and rebuilt my LAMP/Email fedora server as a virtual machine. It took a little time to migrate all my jobs and scripts over, but in the end it was worth it.
I was left with two spare machines that I can sell on craigslist or give away to someone who actually needed a machine (or a space heater!). The machines I did keep are both dual core AMD boxes with plenty of muscle to take on the additional duties of virtualization.
Step 2 - Undervolting/Underclocking
Changing the frequency and voltage of the CPU is nothing new under the sun. People have been overclocking and overvolting their machines for the past 15 years in an effort to extract more performance from their hardware. It wasn't until the last four or five years did people realize that doing the opposite - reducing voltage and clock speed - meant less heat and in turn less electricity consumed. I wanted the benefits of underclocking without taking the performance hit when I really needed some major CPU power.
The solution was CPU Rightmark an open source application that's setup to perform CPU throttling in regards to both clock speed and voltage. This application let me configure both my remaining machines and the wife's laptop to run at a miserly 1ghz and some unholy low voltage (you will need to experiment to determine what's right for your machine. When CPU usage crosses a certain threshold - say 10%, Rightmark will throttle voltage and clock speed back up to 100% and drop it back down once demand drops - all in a matter of milliseconds. Seeing as all my machines don't use more than 2-3% CPU at any given time anyways (unless I'm spending a few hours playing Crysis), Rightmark kept them running cool and quiet.
After several months with the power bill pegged consistently at $120+ (even more in the summer before that), my last two bills have been between $55-$65. In the near future I plan on getting some more concrete numbers through the use of a Kill-a-watt, which measures power consumption at the socket.
