“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

Saturday, December 08, 2007

Total energy use in my family

In an earlier post I utilized data in the World Almanac and Book of Facts to determine that the total per capita rate of energy consumption in the United States is a little over 11,000 watts. I decided to see where my family and I fall into this. I approximated all of the electrical consumers in the house, the fuel consumption of my vehicle, my wife's vehicle, my airplane, the power I use at work, the power she uses at work, the energy content of the food each of us eats, and the energy content of the items each of us "consumes."

Obviously, many approximations and estimations were necessary but the results are quite interesting to me. It appears that my family of four consumes energy at the rate of about 40,094 watts. This is all-inclusive as best I can make it, but does not include our pro-rata share of government expenditures (this could be significant, considering it would include our share of military expenditures of energy, etc.). Surprisingly, this amounts to 10,023 watts per capita in my family. I find this agreement with the figures from the Almanac to be downright startling and, frankly, quite gratifying. It's a little misleading though, since the Almanac figures are the total of U.S. energy use whereas, as we'll see later, a significant portion of my family's energy consumption likely takes place offshore.

The largest single item is my wife's use of automobile gasoline in her Grand Cherokee Laredo. This came to 11,880 watts. She uses a LOT of gas.The next is her consumption of "stuff." I don't know exactly what she buys, so I used the the money she spends as a proxy. I excluded food, since it's included separately, then figured one third the cost represents energy input. In earlier days it would have been less, since there would be more input of labor but in this automated day and age, I figure one third. Then I estimated the cost of a joule of energy (about $2.778*10^-8) and worked back to rate of consumption normalized to represent continuous consumption. Since the two children that share our house are hers, I lumped all consumption that is not mine into hers. The total for this category is 10,400 watts. This is the where the "offshore" portion mentioned above comes in, since a significant portion of the energy input for our "stuff" purchases is in places like China.

Next came my use of automobile gasoline at 5,049 watts, followed by aviation gas for my airplane at 3,961 watts. The house consumes energy at the rate of about 2,812 watts. I used a separate spreadsheet to go item by item in the house, the largest consumer on the continuous, annualized basis is the refrigerator, followed by the swimming pool pump. My goods consumption comes in at 2,400 watts. Total food for the four of us is 3,294 watts. Amazingly, taking my house completely "off the grid" would only reduce our family's total fossil fuel energy expenditure by about 7%. As an aside, I should point out that I'm carrying many more digits of accuracy than my approximations justify, the best of them are probably good for two significant figures.

From a carbon footprint point of view, I assume that 100% of our energy use comes from burning fossil fuels, and that 6 pounds of fossil fuel provides 125,000,000 joules of energy and produces 19 pounds of carbon dioxide. That means that our rate of energy consumption results in the annual addition to the atmosphere of 96 tons of carbon dioxide. From an economic point of view, my family spends something like $35,000 per year on energy.

I mentioned in my article about the Almanac that I was confident I could reduce my rate of energy consumption by half. I'm less confident now that it would be relatively easy, but circumstances will surely force us to do this and much more. At least I now know where to start looking for the savings.


Michael Tobis said...

It would be interesting to compare your methodology to this guy's:


Rob Ryan said...

His analysis triggered some "ah ha" moments of things I'd not considered, in particular, my share of some of the public sector costs such as pavements and public buildings. I also mentioned in the post that I'd not included my share of the cost of our military. So, no doubt, mine is an underestimate.