Exelon Generation officials broke ground Monday for two new power generating units at its Perryman Station in southeastern Harford County, calling the project an expanded focus on natural gas and clean energy.

The two 60-megawatt units, which will run on natural gas, are an addition to five existing units producing 345 megawatts for the central Maryland electrical grid. Four of the existing power units are oil-fired combustion turbines; one is fueled by natural gas.

The Perryman facility is off Chelsea Road near Bush River in an area once covered by farms that is gradually evolving into what Harford County government officials have long wanted: An industrial and distribution hub close to Aberdeen Proving Ground.

Ron DeGregorio, president of Exelon Power, said the new units will be defined by "quality craftsmanship" and signal "the next generation of power."

Roderick Easter, field representative for CHOICE construction employment group, joined DeGregorio and David Sikora, head of engineering and projects at Exelon, and Harford State Sen. Barry Glassman, in turning over the ceremonial first shovelfuls of earth in front of a fenced off construction site.

Perryman Station was originally developed in the mid-1990s by Constellation Energy and Baltimore Gas & Electric, which were taken over by Exelon in 2012.

In the 1960s, BGE acquired 700 acres in Perryman, where a small, oil-fired plant to provide standby power, was later constructed. BGE officials had originally considered the site for a future nuclear power plant, but those plans changed over the ensuing 30 years. When nuclear power lost favor following the 1979 Three Mile Island accident, BGE then briefly considered building a coal fired plant in Perryman but eventually backed away in the face of deregulation of the power production industry and environmental concerns.

Ultimately, BGE/Constellation officials decided to modernize the original facility in Perryman, what is known as a "peaking plant" providing power during periods of high demand.

As with existing units at the plant, the new Perryman units will not be used every day but will be run "regularly" during peak times, such as from 3 to 7 p.m., Exelon spokesman Bob Judge explained.

He noted the electricity will be distributed in Maryland, although he could not say specifically where it would go.

The new units, which will cost $120 million to build, will also be able to run on low-sulphur oil as a back-up, Judge said.

"It's clean, efficient power and it's also going to be very responsive," Sikora said.

The project is "well ahead" of schedule, DeGregorio said. It is expected to be completed by June 2015. Exelon estimates about 95 construction jobs will be created because of the project.

Glassman, a Republican who is running for county executive, thanked Exelon for investing in Harford.

Exelon officials also presented a $1,000 check to Joyce Duffy, of Harford Family House, who told the employees gathered at the groundbreaking that her organization has plenty of opportunities to volunteer.

Exelon produces electricity, and its BGE subsidiary dispenses the power to homes and businesses throughout the region, including to 101,000 customers in southern, central and northwestern Harford County. Another Exelon subsidiary owns Conowingo Dam and its hydroelectric plant in northeastern Harford.

Exelon also is in the process of acquiring Pepco Holdings, another regional electricity producer and distributor, whose Delmarva Power subsidiary has 5,500 customers in northeastern Harford and also serves Cecil County and the rest of Maryland's Eastern Shore counties, as well as the entire state of Delaware.

Collectively, BGE, Exelon and Constellation paid more than $11.5 million in Harford County business property taxes in the 2013 fiscal year, according to the county's most recent annual financial report. The tax revenue from the Perryman facility alone was $1.27 million.