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 supplied by LDCs has ranged between a low of 709.5 million metric tons (MMT) in 2012 and a high of 823 MMT in 2019 and is directly proportional to the quantity of natural gas supplied. The total volume of natural gas supplied increased by 10 percent in 2018 and by 1 percent in 2019 But decreased by 5 percent in 2020. The increase in natural gas supplied in 2018 and 2019 was primarily due to economic growth, relatively low natural gas prices resulting from high levels of natural gas production, and greater reliance on natural gas to fuel power plants. [1, 2, 3] The lower CO2e reported for 2020 is due to a reduction in demand by residential, commercial (which includes restaurants, hotels and schools) and industrial consumers. Natural gas supplied to residential, commercial and industrial customers in 2020 decreased by 7 percent, 10 percent and 6 percent, respectively, compared with 2019, despite the lower natural gas prices.  The decrease in natural gas consumption by residential users is likely due to milder winter weather in January - March 2020 and November – December 2020, while the lower consumption in the commercial and industrial sectors is likely caused by the COVID-19 pandemic closures.  Natural gas consumption by the electric power sector increased by 4 percent in 2020. The increase in natural gas consumed by the electric power sector over the last three years is due in part to low gas prices, the retirement of coal-fired power plants and in 2020 to higher-than-normal summer temperatures. [2, 3, 5].
The reported CO2 for 2011 and 2012 are also affected by changes in the default emission factors. 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 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. However, the total CO2 for the sector is 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. Natural Gas Production, Consumption, and Exports Set New Records in 2019, October 5, 2020. Available at: https://www.eia.gov/todayinenergy/detail.php?id=45377.
 U.S. Department of Energy, Today in Energy, In 2019, the United States Produced and Consumed Record Volumes of Natural Gas, July 10, 2020. Available at: https://www.eia.gov/todayinenergy/detail.php?id=44336.
 U.S. Department of Energy, Today in Energy, In 2020, U.S. Natural Gas Prices were the Lowest in Decades, January 7, 2021. Available at: https://www.eia.gov/todayinenergy/detail.php?id=46376
 U.S. Department of Energy, Today in Energy, U.S. Natural Gas Consumption was Lower in 2020 in All Sectors Except Electric Power, March 10, 2021. https://www.eia.gov/todayinenergy/detail.php?id=47076
 U.S. Department of Energy, Today in Energy, More than 100 Coal-fired Plants have been Replaced or Converted to Natural Gas Since 2011, August 5, 2020. Available at: https://www.eia.gov/todayinenergy/detail.php?id=44636.