Carnegie Mellon University

Power Plant at sunset

June 20, 2017

CMU Power Sector Carbon Index

 From 2005 to 2017, the CO2 emissions intensity from US electricity production has decreased nearly 24%, according to the latest update of the Carnegie Mellon Power Sector Carbon Index.

Yet before index co-creators CEE Assistant Professor Costa Samaras and Engineering and Public Policy Professor Inês Azevedo launched the index earlier this year, such timely insights into CO2 emissions were not only difficult to obtain, but required time-consuming study and expert analysis.

Automating much of the data collection and analysis, their index now serves as a valuable, transparent resource for tracking the US power sector’s CO2 emissions as well as the total electricity generated from coal, natural gas, nuclear, and renewables, with data going back as far as 2001. Using this information, the index reports on emissions intensity, the ratio between total emissions resulting from electricity production and the total electricity produced in a set period.

Overall, the results appear positive. The impressive 24% CO2 decline from peak 2005 emissions has been aided by the rise of renewable energy, with renewables accounting for 19% of electricity generated in first three months of 2017. An even bigger driver behind the lowered carbon emissions intensity has been an increased usage of natural gas, with 2016 being the first year in which the US generated more electricity from natural gas than coal.

Yet, over the last two quarters—from October 2016 to March 2017—coal has grown to again take the lead as our primary electricity source, resulting in carbon emissions intensity increasing slightly over this period. As coal and natural gas prices fluctuate and remain in direct competition, which energy source will win out in the long term remains to be seen, with CMU’s index allowing careful observation of any trends that take shape.

Published through the Scott Institute for Energy Innovation and supported by Mitsubishi Hitachi Power Systems, the index has benefits that extend far beyond the CMU community. For policy makers and regulators, having a current understanding of the power sector’s contribution to climate change and their de-carbonization progress can enable improved decision-making. Likewise, utility companies can use the index to compare their CO2 reductions with national trends—and Samaras and Azevedo expect the index to soon incorporate regional data as well.
“With every update we post, new insights arise that are of high relevance to the nation’s energy leaders and policy makers, enabling them to assess the level of effort still needed for deep de-carbonization activities in a timely manner,” says Azevedo, who also notes that the index will highlight the consequences of various changes in energy markets and policies.

Even everyday citizens can find value in the index, says Samaras. “The public is increasingly concerned about climate change, and they want to be able to do something about it. The index lets them know how the country is doing over time and helps them to understand some of the contributing factors to the climate.”

To maximize the impact of the index, the underlying code, figures, and data are all available for download and public use. “Having these pieces out in the open is essential for the future of energy analysis, so that other people can build on this work that we started,” Samaras says. “For us alone to become experts on carbon emissions doesn't help anybody. That wouldn’t advance knowledge or impact climate change, but we believe this index will. Those are the most important goals of our work.”