How much energy can each man, woman, and child on Earth use sustainably? According to a consortium of European scientists, it's 2000 watts. That's 17,520 kilowatt hours per year per person. Like most nice, tidy numbers, that number is probably more or less fictitious (there's the question of where the energy comes from, and how you calculate the per-capita consumption, just off the top of my head), but it's good to have a starting point for thinking about it. And an article in this week's New Yorker, by Elizabeth Kolbert, does a pretty good job of working through that thought process.
My household electricity usage comes to a little less than 7,200 kwh in the last year - my provider, Avista actually has some great online tools for assessing home energy efficiency, and even allows me to specify that I only buy power from wind and other renewable sources. Unfortunately, my personal energy budget includes more than home light and heating: there's auto fuel, electricity used at work, and the energy used to produce and transport almost everything I buy, just to name a few. It's a pity there's no good way to sum all those up.