Q805. What factors could have influenced trends in GHGs associated with natural gas supply?
A805. In general, the CO2 associated with natural gas supplied by local distribution companies (LDCs) varies due to fluctuations in weather, the relative price of natural gas compared to other fuels and the prevailing economic conditions. The annual CO2 reported for natural gas supply has ranged between a low of 709 million metric tons (MMT) in 2012 and a high of 815 MMT in 2018. The 2018 emissions were higher than previous years primarily because of the continued economic growth and a warmer than normal summer that resulted in higher electricity usage for air conditioning.
The reported CO2 was also affected by changes in the default emission factor. The default emission factor for natural gas supplied was revised in 2013 to a value about 1% less than the default emission factor used in years prior to 2013. For an LDC that uses the default emission factors, the total CO2 value reported by in 2013 and subsequent years is 1% lower than would have been reported if the emission factor had not been updated. Since many LDCs use emission factors developed using their own data, the overall impact on CO2 for the sector is small, with the total CO2 for the sector being lower for 2013 and subsequent years than would have been reported if the emission factor had remained unchanged.
 U.S. Department of Energy, Today in Energy, U.S. Energy-Related CO2 Emissions Increased in 2018 But Will Likely Fall in 2019 and 2020, January 28, 2019. Available at: https://www.eia.gov/todayinenergy/detail.php?id=38133.