Comparing Q3 2017 to Q3 2016

The Carnegie Mellon Power Sector Carbon Index provides a comprehensive picture of the carbon intensity of electricity production in the during the previous 12 months and over an extended period to 2001. The CMU index also provides a summary of how much electricity generation is from coal, natural gas, nuclear, and renewables. According to the Carnegie Mellon Power Sector Carbon Index, U.S. power plant emissions averaged 1,035 lb CO₂ per MWh in the third quarter of 2017, which was down 5 percent from the same time frame in 2016. Continuing the trend seen in Q2 2017 and the first three quarters of 2016, more electricity was generated from natural gas than from coal. Electricity generation from renewables was 10% higher in the third quarter of 2017 when compared to the third quarter of 2016.

Comparing Performance in 2017 to 2005

The Power Sector Carbon Index for Q3 of 2017 was 22% lower than in the annual value in 2005, from 1,324 lb CO₂ per MWh to 1,004 lb CO₂ per MWh (or 600 to 470 g CO₂ per kWh). As of Q3 of 2017, the rolling annual average carbon intensity was 981 lb CO₂ per MWh (or 445 g CO₂ per kWh), which is 26% lower than the annual value in 2005.

Highlights of the 2017 Q3 Results

• The Power Sector Carbon Index was down by 5% in Q3 2017 when compared to Q3 2016.
• Total electricity generation was down 5% in Q3 2017 when compared to Q3 2016.
• Coal generation was down by 10% in Q3 2017 (346 million MWh) when compared to Q3 2016 (386 million MWh). Coal represented 30% of total generation in Q3 2017.
• Carbon intensity of coal generation in Q3 2017 was about the same as in Q3 2016 (2,240 lb CO₂ per MWh and 2,248 lb CO₂ per MWh, respectively).
• Natural gas generation was down by 7% in Q3 2017 (401 million MWh) when compared to Q3 2016 (432 million MWh). Natural gas represented 36% of total generation in Q3 2017.
• Carbon intensity of natural gas generation was up 1% in Q3 2017 (944 lb CO₂ per MWh) when compared to Q3 2016 (935 lb CO₂ per MWh).
• Renewable electricity generation was up by 10% in Q3 2017 (156 Million MWh) when compared to Q3 2016 (142 million MWh). Renewables represented 14% of total generation in Q3 2017.
• Nuclear electricity generation was up by 2% in Q3 2017 (212 Million MWh) when compared to Q3 2016 (207 million MWh). Nuclear represented 19% of total generation in Q3 2017.
• Total direct CO₂ emissions from the power sector in Q3 2017 were 528 billion metric tons, down 10% from 584 billion metric tons in Q3 of 2016.

Final EIA and EPA Data and Revisions to Previous Results

The Power Sector Carbon Index uses the most recent data released by EIA and EPA, including preliminary data that may change slightly upon final release by EIA and EPA. Some of the minor revisions in our past results include:

• Power Sector Carbon Index results for the second quarter of 2017 are revised down 8 lb CO₂/MWh from 947 to 939 lb/MWh. This change resulted from increases in estimated natural gas generation (2.4 million MWh), decreases in estimated coal generation (1.3 million MWh), and increases in estimated renewable generation (0.5 million MWh).
• Power Sector Carbon Index results for the first quarter of 2017 are revised down 7 lb CO₂/MWh from 954 to 947 lb/MWh. This was largely due to an increase in estimated natural gas and renewable generation (4.3 and 0.7 million MWh), and a small decrease in coal generation (0.6 million MWh).
• Power Sector Carbon Index results for 2016 are revised down 4 lb CO₂/MWh from 1,005 to 1,001 lb/MWh. A decrease in emissions intensity of natural gas generation is partially responsible for this change.