Analyzing variability and decomposing electricity-generation emission factors for three U.S. states

EF: emission factor; EGEF: electricity generation emission factor; NG: natural gas; Pet: petroleum; FF: fossil fuel; eff: efficiency; GWP: global warming potential, AP: acidification potential, HH: human health, EA: eutrophication air, EW: eutrophication water, SA: smog air. [Display omitted] •Variability in emission factor of fossil fuels can alter the annual electricity-generation emission factor.•Variability among electricity-generation emission factors on an annual basis is compared for three U.S. states.•SO2 and NOx emissions factors show higher variability than CO2 emission factors.•The main factor driving reductions in the electricity-generation emission factor for the three states is different.•Environmental impact categories related to SO2 and NOX are more variable than categories related to CO2 emissions. Electricity generation emission factors (EGEF) quantify the relationship between amount of pollutant emitted and amount of electricity generated. Quantifying variability among calculated EGEFs is important when EGEFs are used for decision-making. Variabilities in EGEF on an annual basis due to variability in the amount of coal, natural gas, and petroleum emissions within the fuel mix are quantified for California, Texas, and New York in 2017. The results show a higher coefficient of variation for SO2 and NOx compared to CO2 EGEF. Changes in the EGEF over time are studied using decomposition analysis for California, Texas, and New York from 1990 to 2017. The results show that the main factor in reducing EGEF in California is the improving generation efficiency of power plants; in Texas, it is the increasing ratio of renewable to non-renewable electricity generation; and in New York, it is the changing mix of fossil fuels that are consumed for electricity generation. The effect of variability in EGEF on environmental impact categories is analyzed. Eutrophication of air, eutrophication of water, and smog formation are subject to high uncertainty because SO2 and NOx EGEFs are used to quantify these impacts, whereas global warming potential has less uncertainty because it only uses CO2 EGEF.