https://www.sciencedaily.com/releases/2020/05/200508184601.htm

In "The European Union Emissions Trading Scheme and Fuel Efficiency of Fossil Fuel Power Plants in Germany" author Robert Germeshausen studies German power plants and finds that a reduction in fuel use by fossil fuel power plants due to the introduction of the EU ETS translates into reductions in total annual carbon emissions of about 1.5 to 2 percent within the German power sector.

To put this improvement into context, this decrease in fuel input on average is equivalent to a reduction of around four to six million tons in annual carbon emissions. The results point to the role of actual investment in generation technology to improve fuel efficiency as Germeshausen finds positive effects on large investments in machinery.