The experiment took place in the fall of 2013, with alternating control and energy-saving weeks.
When it was done, Rohan concluded that when everyone was minding their energy use, the family achieved a 23 percent decrease in their carbon footprint. Then he used data from the U.S. Census to extrapolate the emissions that would be avoided if half of all households in Pittsburgh did the same. Then half of homes in Allegheny County, then Pennsylvania, and then the U.S. as a whole.
The grandest scenario amounts to a 200 million ton reduction in total carbon dioxide emissions — about 4 percent of the nation’s carbon footprint.