Synopsis: The Antitrust Division of the Department of Justice (DOJ) and the Federal Energy Regulatory Commission (FERC) purport to apply the same analytical framework to analyze the competitive effects of electric power mergers. In practice, however, the DOJ and the FERC take very different approaches. The FERC relies largely on market concentration screens to determine whether a merger is likely to result in anticompetitive effects; the DOJ, on the other hand, relies on a wider range of evidence to assess anticompetitive effects. In this article I explain differences between the FERC and the DOJ using a "cost minimization" framework that accounts for the error costs (the costs of …