That wasn't necessarily the company's biggest drama during Shattuck's tenure — or even the biggest involving a merger. In 2006, amid widespread customer and political outrage over spiking electricity rates, Constellation called off an attempt to sell itself to the parent of Florida Power & Light.
BGE bills were set to rise 72 percent, which Constellation attributed to the hike in energy prices following Hurricane Katrina and the end of a six-year freeze on residential electricity rates. The announcement set off a furious debate about energy deregulation — already in motion before Shattuck took over — and prompted the General Assembly to temporarily limit the increase to 15 percent.
Given the ups and downs, electric utility analyst Paul Fremont said Shattuck had a "mixed record" at Constellation. He pointed to Shattuck's deal-cutting to get the company out of trouble as an example of a positive for shareholders.
Fremont, with Jefferies & Co., doesn't think Shattuck is being forced out of Exelon.
"I … have not heard of any pressure for him to make that decision," he said.
Shattuck said he didn't get any. He said he's looking forward to not working 80-hour weeks, spending more time on philanthropy — including his family's minority scholarship program — and figuring out the next steps.
"I don't know exactly what yet," he said.
Shattuck isn't walking away with severance or change-in-control payments related to the merger, according to Exelon filings. Retirement makes him eligible for payouts from his deferred compensation, for accelerated vesting of unvested equity awards and for his pension.
The value of the equity awards and deferred compensation was unclear Friday. Exelon did not disclose the value of Shattuck's pension when he retired, but it was $63 million in December, according to a U.S. Securities and Exchange Commission filing.
Exelon said Friday that Shattuck participated in Constellation's executive pension plan, which was in place before he joined the Baltimore company.
Musing over the last decade and a half in the Friday interview, Shattuck said it is his view that both Constellation and Alex. Brown needed to hook up with sizable suitors.
"Both of these businesses are nationally competitive," he said. "All the smaller to midsized investment banks went through similar transactions. … [And] it has been a very tough environment for the merchant power companies — both Constellation and Exelon are much stronger together than they would have been apart."
When Maryland's Public Service Commission approved the merger with Exelon, members expressed misgivings about a deregulated, publicly traded company running a regulated utility — something set in motion many years before.
"It is not obvious to us that tying our regulated utility companies to this business model will be good in the long run for ratepayers or regulated utilities," commissioners wrote. "Having watched major financial institutions become 'too big to fail,' we wonder too if further consolidation in the electricity sector could expose BGE to a wider range of unregulated business risks."
Shattuck said he believes the merger does benefit BGE customers. He said BGE and Exelon's other utilities — ComEd in Illinois and PECO in Pennsylvania — are learning from each other about the best ways to restore electricity after storms, upgrade the power grid and the like.
"I really feel confident that the BGE customers are going to benefit from that over the course of time," he said.
Mayo A. Shattuck III
Title: Non-executive chairman of Exelon Corp.
Background: CEO of Baltimore's Constellation Energy Group for 10 years before selling the company to Exelon; president of Alex. Brown, the Baltimore investment house, before helping to sell it to Bankers Trust New York
Other activities: Member of various boards, including Johns Hopkins Medicine, Gap and Capital One; co-chairman of the Center for Strategic & International Commission on Nuclear Policy in the United States