With the amount of computer power in your homes many of you could run a small nation and probably do, although it's likely to be virtual. You're still probably not as extreme as the president of our division, Bob Muglia, and his home data center. But, that’s no excuse for not thinking about the energy efficiency of your equipment. See Ade’s blog entry on thinking like a data center engineer.
He's calculated the PUE for both the gaming/developer machine he built recently and the energy efficient Windows Home Server he built last year. Interesting stuff, especially using killing zombies as a method to ensure your machine is under full load. I'm sure that skill will come in handy when we have to deal with World War Z.