This analysis assesses the then state of knowledge (2011) about the average GHG footprint of average coal and natural gas-fired electricity generation, how the growing share of natural gas production from shale formations could change this GHG footprint at the margin, and what the findings imply for policymakers, investors and the environment. The analysis finds that EPA’s updated estimates of fugitive methane emissions from natural gas systems are of concern as a GHG and require further attention. Base case comparisons are calculated on a kg CO2e / MMBtu basis for delivered fuel, which depicts more accurately the energy that is actually available to the power plant versus other calculation methodologies. In determining the emissions factors for the combustion of natural gas and coal, the authors relied on Subpart C of EPA’s Greenhouse Gas Reporting Program which provides GHG emissions on an MMBtu basis of delivered fuel. These results were then converted to aMWh basis to account for differences in coal and natural gas power plant efficiencies. Read all push.