In this paper we investigate the influence of fugitive methane emissions from coal, natural gas, and shale gas extraction on the greenhouse gas (GHG) impacts of fossil fuel power generation through its life cycle. A multiregional hybridized life cycle assessment (LCA) model is used to evaluate several electricity generation technologies with and without carbon dioxide capture and storage. Based on data from the UNFCCC and other literature sources, it is shown that methane emissions from fossil fuel production vary more widely than commonly acknowledged in the LCA literature. This high variability, together with regional disparity in methane emissions, points to the existence of both significant uncertainty and natural variability. The results indicate that the impact of fugitive methane emissions can be significant, ranging from 3% to 56% of total impacts depending on type of technology and region. Total GHG emissions, in CO2-eq./kWh, vary considerably according to the region of the power plant, plant type, and the choice of associated fugitive methane emissions, with values as low as 0.08kg CO2-eq./kWh and as high as 1.52kg CO2-eq./kWh. The variability indicates significant opportunities for controlling methane emissions from fuel chains.