(June 2012) Exelon Generation named Ron DeGregorio president of Exelon Power. Most recently he was chief integration officer working on the Exelon-Constellation merger. Former NSTAR president, chairman and CEO Thomas J. May was elected president and CEO of Northeast Utilities (NU) following the completion of the merger of the two companies. He succeeds Charles W. Shivery, who retired from his position and assumed a new role as the non-executive chairman of the board of NU.