Every so often I recalculate my household’s carbon footprint.
It’s not hard to do. You don’t need pinpoint accuracy. Estimate how much gasoline you buy for your cars. Every gallon of gas you burn generates around 20 pounds of C02. Go to your electricity supplier and find out how many kilowatt-hours you use. You can easily find the average pounds of C02 per KWH from (e.g.) the U.S. EPA eGRID. Go to your natural gas supplier and get your annual consumption in therms, where each therm you burn generates a bit under 12 pounds of C02. If you fly a lot, or use other transportation modes a lot, you’d probably want to add in a separate section for that.
For me, this is a way of keeping oriented on what matters (and what mostly doesn’t) in terms of carbon footprint. It’s also a way to see the tangible results of switching to more energy-efficient and carbon-sparing equipment and fuels.
Every time I redo this calculation, I use it to assess whether there are yet more ways in which I can reduce my carbon footprint. Which is, really, the whole point of doing the calculation in the first place.
Above, in terms of items that we consume every year, the only big item that’s missing is food. It takes a lot of fossil fuel calories to produce one edible calorie. And over the course of a year, you eat a lot of food. Depending on which source you believe, it takes between 7 and 10 fossil-fuel calories to produce and deliver the average U.S. edible calorie. Best guess, food would come in second only to electricity, in terms of our household carbon footprint. But for a lot of reasons, it’s tough to put it on the same page as the other items. So I don’t show it here.
More-than-halving my household carbon footprint in four not-so-easy steps.
The red circle represents the death of my old gas furnace and water heater. I replaced those with a single 97%-efficient gas unit. That cut my gas consumption roughly in half. That’s as much a testament to the age and condition of what I replaced as it is to the efficiency of the new combined heat and hot water unit.
The teal circle is the combined effect of adding insulation to my house attic (small), and adding insulated siding to my house walls (large). My house was built in 1959, and it did not even occur to me that the builder might not have insulated the walls. But — surprise — he didn’t. I eventually figured that out via a simple set of temperature measurements on a cold evening. (You can infer R-value based on the difference in temperature between the outside and inside wall surfaces. E.g., if the inside of the wall is really cold in winter, it’s probably not very well insulated.) Additionally, the only insulation in half the attic was radiant barrier, which had long since decayed.
Insulation is a game of diminishing marginal returns. That first inch or two is worth as much as the next foot. Much of my house lacked that first inch. So I was able to get a considerable drop in energy use. Because, apparently, in the 60+ years that this house has been standing, nobody ever thought to insulate it. Until I did.
The purple circle is the result of reducing our fleet of cars to a single plug-in hybrid, a Prius Prime. Most of our miles are now powered with electricity, and as a result, our C02 emissions from gasoline are negligible by U.S. suburban standards. So now, most of the emissions from local vehicle transport are part of the electricity figure, which makes the drop (in gasoline use) look more dramatic than the actual decline in energy used for transport.
The yellow circle is due to the Obama-era Clean Power Plan, combined with ultra-cheap natural gas driving coal from the electricity-generating marketplace. Together, those made a huge dent in the amount of C02 generated for every KWH of electricity used. My electricity use actually went up over this period. But the Virginia grid got so much cleaner, so fast, that my electricity-related emissions fell. Not due to anything I did, but due to carbon emissions per KWH, for Virginia, falling roughly in half over the past decade or so.
The last two circles show why every civilized nation on earth is trying to shift people toward electrically-powered transport. Using the extremely conservative EPA mileage for my wife’s Prius Prime (54 mpg/ 5 miles per KWH), in Virginia, electrical miles in that Prius now produce one-third as much C02 as gas-powered miles.
Don’t pull a muscle patting myself on the back.
Here are the two key takeaways:
- I’m not alone.
- I’m doing moderately better than average.
The way to see that is to look at the carbon intensity of the U.S. economy as a whole. In a world, C02 emissions per dollar of real Gross Domestic Product.
Source: U.S. EPA
I’ve managed to cut my household C02 emissions about 60 percent, compared to where I was in the early 2000s. Which sounds pretty good.
But over that same period, the average per capita for all Americans has fallen about 30 percent. The average per dollar of real GDP fell by about 30 percent as well.
So, starting from an old, essentially un-insulated house, with ancient and inefficient appliances, and non-hybrid vehicle, I’ve been able to cut my C02 emissions about twice as fast as the average American. That’s a good thing, but it’s hardly an outstanding thing. It’s just the result of keeping your eye on the ball, and having a goal in mind.
The only thing I will say is that, over this entire period, for long-term investments like housing, appliances, and vehicles, I have never regretted purchasing the most energy-efficient option that I plausibly could.
