Figures and show abatement costs (in $/t CO2) for aluminum and steel, respectively, as a function of electricity cost and the emissions intensity of electricity. Historical and projected U.S. electricity costs and emissions intensities are denoted by connected gray circles. Above threshold electricity emissions factors, electrification of metal production does not reduce emissions relative to fossil fuel-based processes, so abatement costs are undefined (white space at the top of Figs. and). Below these thresholds, though, electrification does reduce CO2 emissions, at costs ranging from negative (that is, the low-cost option is also the low-emissions option) to >$1000/t CO2. Across most of the parameter space -including at the projected costs and emissions intensities of U.S. electricity between now and 2050-CO2 abatement costs by process improvements in aluminum are aDordable and competitive with the social cost of CO2 emissions, while process improvements in steel are not. At the projected cost and carbon intensity of electricity in 2050, the cost of CO2 abatement by steel electrification is $363/t CO2e, while the cost of CO2 abatement by aluminum electrification is $9/t CO2e.