American climate-change activists point to Europe, and especially Germany, as the paragon of green energy virtue. But they ought to look closer at Angela Merkel’s political struggles as she tries to form a new government in Berlin amid the economic fallout from the Chancellor’s failing energy revolution.

Berlin last month conceded it will miss its 2020 carbon emissions-reduction goal, having cut emissions by just under 30% compared with 1990 instead of the 40% that Mrs. Merkel promised. The goal of 55% by 2030 is almost surely...