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Carbon Calculators
I decided to take a look at carbon calculators out of curiosity. I wanted to see how much carbon dioxide (CO2) my household was tossing off every year. At it turns out, there are a ton of carbon calculators floating around out there and none of them return the same results. I also found that while it's easy to find a carbon calculator, it's harder to get at the so what of, "if I change my behavior, what's the impact?" This is important because if you can't measure it, it won't happen. People need this level of transparency to make informed decisions. Some carbon-reducing activities (e.g., eating more organic food) cost money. Other activities (e.g., turn off lights, turning down the thermostat) save money, an others, like recycling, are cash neutral.
You might be wondering, "how does this tie into Excel?". Great question. I started out by building a simple model to capture my monthly utilities bills, annual flights, and annual mileage. I've since expanded it to allow modeling of cost savings based on hitting various energy conservation goals (e.g., reduction in miles, reduction in utility bills, etc). Now that's worth something.
Conclusions and Comments
I looked at a total of 11 sites and calculated a carbon footprint from 7 of them. Overall, I'd have to say that Carbon Footprint was my favorite, followed closely by the EPA site. Both are easy to use, break out carbon output by major activity, and have a good level of detail which lets you model changes in behavior. Anyways, the 11 sites I visited are:
| Website | Comment |
|---|---|
 | Carbon Footprint. My pick. Good combination of detail and ease of use. |
 | EPA site. Provides some nice detail about green practices; downloadable calculator in Excel format, which shows calculations. This site also calculated you footprint in thousands of pounds, which I converted -- though I may have to go back and double check my conversion. |
 | Zerofootprint. Their One-Minute Calculator is very fast to use and nicely presented on a single page, though it doesn't allow for much detail such as multiple cars, recycling habits, or your home energy use. You can sign up for a personal carbon manager on the site, but this requires registration, which I decided to pass on. |
 | Climate Crisis. A little too simplified for me, though very easy to use. Didn't break out carbon values by activity, and couldn't accomodate multiple cars. |
 | My Carbon Footprint. Doesn't really calculate your footprint, rather it tells you how much you could save by adopting various measures. Good supporting site, but you'll have to do conversions from metric units of measure. |
 | Safe Climate. Only offers calculations for the EU; did not complete calculations |
 | Nature.org. Provides a nice level of detail but the carbon estimate is much higher than any other calculator and I couldn't really figure out why. |
 | BP site. Another site that ask questions at an interesting level of detail, but only offers up an aggregate carbon value. The rest of the site does go into more detail about green practices. |
 | Yahoo. Decent, basic calculator. |
 | Conservation.org. I didn't like this one at all. It really turned me off. The carbon figures didn't foot and the "ads" for offsets kept getting in the way. A little too over the top in my opinion. |
 | Life Goggles. Does not provide their own carbon calculator but links to several and offers tips on how to reduce carbon footprint. Does offer a nice glossary of green terms. |
How To
At a minimum, before you start, you should grab a copy of your latest utilities bill, have some idea of how many miles you drive annually, and how many flights you take. If you have that information, sit down, visit one of the sites and have fun. You can certainly start out with high level estimates, but I found it useful to write a quick model to help me calculate more accurate figures for my household.
Methodology
First off, my methodology was hardly scientific, though I found it interesting. I took my household (4 persons, attached housing, 2 cars, with a moderate amount of flights) and tried to plug the same values into all of the sites I "tested". I took all of the by-activity carbon values and plugged them into a comparative table, shown below (also included in the file linked above). I was really just trying to see what my values looked like, compared to the US average, across a number of sites.
Findings and Conclusions
The first thing that jumped out was that everyone site generates a different value. In some cases, the values are orders of magnitude different, so each site may have a different calculation methodology, set of assumptions, or base definition of what is or is not included in your carbon footprint. However, based on my household, our driving habits, and flights, the Carbon Footprint calculator shows me as contributing 17.8 tons per year compared 20.75 tons/year for the average US household. OK, so what. What do you do about it? My carbon contribution breaks down as follows:
| Activity | Tons | % of Total |
|---|---|---|
| Driving | 7.262 | 40.9% |
| Household excluding Utilities | 6.408 | 36.1% |
| Flights | 3.056 | 17.2% |
| Utilities | 1.024 | 5.8% |
| Total | 17.75 | 100.0% |
| Average | 20.40 |
Here is the summary table of carbon values for the 7 calculators I actually completed.
| Source Calculator | Driving | Lifestyle | Flights | Utilities | Waste | Total | US Average |
|---|---|---|---|---|---|---|---|
| Carbon Footprint | 7.26 | 6.41 | 3.06 | 1.02 | NA | 17.75 | 20.40 |
| EPA | 8.44 | NA | NA | 7.46 | 1.19 | 17.08 | 20.75 |
| Zero Footprint | 7.45 | 6.32 | 2.04 | NA | NA | 15.81 | 13.00 |
| Climate Crisis | 8.00 | NA | 2.65 | 0.40 | NA | 11.05 | 7.50 |
| Nature.org | 14.00 | 22.80 | 8.70 | 18.00 | NA | 63.50 | 110.00 |
| BP | NA | NA | NA | NA | NA | 23.00 | 19.00 |
| Yahoo | 7.00 | NA | 20.40 | 5.50 | NA | 32.90 | 9.44 |
Armed with this information, I can make some educated choices about what, if anything, I can do. Certainly, driving is the largest contributor, which I can reduce by either decreasing total miles driven, or improving my gas mileage. The first option probably involves inconvenience (e.g., carpooling, making my wife pick up the kids, etc), not all of which are going to be popular. The second option might involve cost, but it might also simply require some behavior changes like reducing driving speed, ensuring tires are properly inflated, etc. You can some of the calculators with higher levels of detail to calculate carbon output for different sets of behavior, log them into your spreadsheet, and then calculate the difference. You can also track your utilities usage and driving habits to see if your changes in behavior are paying off.
So, what can one person do?
I ran across this site, Ideal Bite in a magazine, which bills itself as a, "good source of advice for real people leading busy lives." It was linked to an article in Working Mother magazine about quick and simple ways to start making a difference ... and save money. I took a read through that and there lots of very practical, easy to implement ideas, like simply adopting on-line banking and bill pay or stopping marketers from mailing you catalogs and credit card offers. Definately worth the read.
What exactly constitutes a "ton of carbon"?
The BP site had this description. 1 ton of CO2 emissions occupies 556 m3 (cubic meter) of space at 25 degrees Celsius and standard pressure. The volume of water in an Olympic swimming pool is approximately 2500m3. Therefore the average household CO2 emissions in the UK (approximately 10 tons per year) would be enough to fill about two Olympic swimming pools and the average household emissions in the USA (approximately 20 tons per year) would be enough to fill about four and half Olympic swimming pools!
So, there you go. One person's quick dip into the pool of carbon calculators. I may test some more later, as my curiousity is now piqued, and I'll write those up as I go.
Notes
| Last updated | 4/14/08 |
| Application Version | None |
| Author | Michael Kan |
| Pre-requisites | None |
| Related Tips | None |