In 1996, Riverfront Stadium in Downtown Cincinnati was renamed "Cinergy Field" in a sponsorship deal with Cinergy. The stadium was demolished by implosion in December 2002 to make way for Great American Ballpark.
In 2005, Cinergy announced a friendly acquisition by the larger Charlotte, North Carolina-based Duke Energy. The acquisition was completed on April 3, 2006. The combined company retains the Duke Energy name. Until the acquisition, Cinergy still operated under the names of the three local utilities (e.g., Cinergy/CG&E in Cincinnati); since the acquisition, the names of the three former Cinergy utilities and Duke Power, the former Duke Energy utility subsidiary, have been phased out, although signs bearing the former logos still remain at some substations.
Researchers at the University of Massachusetts Amherst have identified Cinergy as the 49th-largest corporate producer of air pollution in the United States, with roughly 29 million pounds of toxic chemicals released annually into the air. Major pollutants indicated by the study include sulfuric acid, hydrochloric acid, chromium compounds, and manganese compounds.