Abstract Our work provides refined tests of the source of merger gains in a neglected industry: utilities. Utilities offer fertile ground for analysis of traditional theories: synergy, collusion, hubris, and anticipation. Utility mergers create wealth for the combined firm, consistent with both the synergy and collusion hypotheses. To distinguish between these hypotheses, we study rival stock returns across dimensions related to collusion: deregulation, geography, and horizontal and withdrawn deals. We also find that the impact of mergers on consumer prices is consistent with synergy rather than collusion. Analysis of industry rivals that become targets also rejects collusion and is consistent with anticipation.