I’ve been wondering what the inputs and outputs are of my home energy usage. For some months now, I’ve used a CurrentCost Envi to track my house’s energy usage, so I know the numbers in kilowatt hours: 8,166 kWh in the past 12 months, an average of 680 kWh/month, with a low of 454 kWh (September 2010) and a high of 1,180 kWh (January 2010). But what does that mean?
My power comes from approximately an equal mix of coal and nuclear, according to Dominion, my power company. Let’s start with coal.
Although not all coal is created equal, it basically takes one kilogram of coal to generate two kilowatt hours of electricity. Coal itself contains rather more power, but a lot is wasted as heat in the generation process, and still more is lost in the distribution process. Of my 8,166 kWh, about 4,093 kWh came from coal. That means that 4,511 pounds of coal were burned to power my home in the past year. The pollution side of coal is rather worse. Each unit of coal results in the emission of 2.93 times as much CO2 by weight (assuming 80% carbon coal), a result of carbon emissions bonding with oxygen. The coal burned to power my home, therefore, resulted in 13,217 pounds—six and a half tons—of CO2 to be emitted.
Nuclear is rather different, at least by weight. Uranium produces 360,000 kWh per kilogram, meaning that the 4,093 kWh of nuclear power for my home required 1.2 grams of uranium, which is approximately half of the weight of a penny, and slightly more than a paperclip. The amount of waste is similarly minute, in quantity. Uranium generates 3 milligrams of waste per kilowatt hour, or the size of a standard-issue snowflake. For my home’s usage in a year, that’s 12 grams of nuclear waste, the weight of two quarters. Of course, a straight comparison of uranium to coal by weight isn’t particularly meaningful.
None of this considers the mining or transport of that coal or uranium, the storage of the waste, etc. But I find it useful to know that powering my house for the last year required a over two tons of coal, a single gram of uranium, and produced north of six tons of CO2 and twelve grams of nuclear waste.
For the record, I participate in Dominion’s Green Power program, meaning that I pay 1.5¢ extra per kWh to offset 100% of my power use via renewable sources. But those very electrons don’t travel to my home—they just get mixed into the regional grid. So while I can feel good that I have prevented all of the enumerated energy sources and pollution from being used and emitted on my behalf, I’m not kidding myself—it’s 98% coal and nuclear power that’s coming into my home.