  Recent studies conclude that the global coronavirus (COVID-19) pandemic
decreased power sector CO$_2$ emissions globally and in the United States. In
this paper, we analyze the statistical significance of CO2 emissions reductions
in the U.S. power sector from March through December 2020. We use Gaussian
process (GP) regression to assess whether CO2 emissions reductions would have
occurred with reasonable probability in the absence of COVID-19 considering
uncertainty due to factors unrelated to the pandemic and adjusting for weather,
seasonality, and recent emissions trends. We find that monthly CO2 emissions
reductions are only statistically significant in April and May 2020 considering
hypothesis tests at 5% significance levels. Separately, we consider the
potential impact of COVID-19 on coal-fired power plant retirements through
2022. We find that only a small percentage of U.S. coal power plants are at
risk of retirement due to a possible COVID-19-related sustained reduction in
electricity demand and prices. We observe and anticipate a return to
pre-COVID-19 CO2 emissions in the U.S. power sector.
