How do we figure out the reduction in heat-trapping gases, particularly Carbon Dioxide (CO₂)?

We use the best numbers available for determining how much energy an action saves, usually in the form of electricity or natural gas. We then use information from the U.S. Energy Information Administration and Environmental Protection Agency to translate the energy savings into carbon dioxide savings. For more information about this conversion, see the EPA Power Profiler.

It may seem impossible that CO₂, a gas, is routinely measured by weight, but that just goes to show how much carbon dioxide we actually release into the atmosphere. The average American is responsible for the release of 44,000 pounds of carbon dioxide every year. Our numbers, which we talk about below, are based on certain assumptions and are estimates. They don’t exactly reflect what each individual is doing, but we’ve done our best to make sure they’re close. 

Here our the calculations and assumptions for September 2010.