If every one of the 110 Million households in the USA changed just one light bulb to CFL, this would reduce the total output of CO2 emissions in the United States by around 2.6%. Do I have my math right? What assumptions are going into this. It seemed kind of implausible, to be honest. But I think the numbers check out. Have I made an error?
So first, read the What You Can Do page of the Inconvenient Truth website, which claims:
If every family in the U.S. made the switch, weâ€™d reduce carbon dioxide by more than 90 billion pounds!
Now consider the following image, produced by the US Department of Energy’s “Carbon Dioxide Information Analysis Center” which produced this data: .
In 2003, we produced about 130 teragrams of CO2 per month. If we’re talking about the same CO2, then it’s pretty easy math to see what share of that 130 Tg/month comes from the 90 billion pounds of CO2 saved.
Ok, first, what’s 130 x 12 teragrams in pounds: answer from Google is 3.43921129 Ã— 1012 pounds per year. So what percentage of this is the 90 billion pounds saved? Just ask Google: 90 billion / (3.43921129 Ã— 10^12) in percent? Answer: 2.62 percent.
Minor conclusion: Google’s calculator is awesome!
Main conclusion: If we all changed one light bulb to CFL, we would reduce carbon emissions by 2.6%. Holy mackerel!
Source and Assumptions
This page from Greenlights USA, seller of Compact Fluorescent Bulbs (CFL) does a great job of showing how they arrived at a similar (larger, actually) result for the 90 Billion Lbs CO2 claim. All of their sources are from US government measurements, and are conservative, if only because they are outdated. The same conclusion is reported on the Energy Star website.
Ok, so one key assumption of this calculation may be questionable. 101 Billion kWh of electricity were used for residential lighting in 2001. If you change an incandescent bulb, it has to be one that represents at least an average use of light in your house — the bulb I replaced in the utility room that I turn on for five minutes every week or two doesn’t really count. The ones in our bedroom, living room, and office, outdoor floods and the basement playroom are certainly in the normal use zones. So, make your bulb count. Or better yet, recognize that not everyone is going to replace a bulb, so maybe do three or four (or 15 – 20, which we did).
The only thing I am not sure about here is whether the CO2 emissions are comparable. But I think so. Please let me know if I have made an error.
So if this is right, that’s a damned impressive statistic.