The U.S. Department of Energy’s (DOE) offices in Germantown, Md., will soon cut their energy costs thanks to new photovoltaic arrays being installed by Pepco Energy Services. The company will install two arrays, totaling 352 kilowatts (kWs) of photovoltaics that will help offset the building’s use of grid-supplied electricity.

The $2.3 million installation will consist of a 300 kW rooftop array and a 52 kW photovoltaic carport with a car charging station. DOE is funding the project with American Recovery and Reinvestment Act (ARRA) money, said Pepco’s Director of Federal Projects John Dukes.

“The agency is going to retain ownership for the system,” he said.

Pepco Energy Services, a subsidiary of Pepco Holdings, Inc. (NYSE: POM), said both the ground array and the carport array will be operational by July 2011. When completed, the system will include web-enabled monitoring, Dukes said.

“They’re also going to get a kiosk in the main lobby to show visitors and dignitaries,” he said.

The projected savings are significant, Dukes said.

“They’re going to offset costs by a quarter of a million dollars in 2010 energy rates,” he said. Given that energy costs are continuing to rise in Maryland—prices were roughly 6 cents per kW hour in 2000 and rose to more than 10 cents per kWh in 2010—savings in future years could be even greater.

If electric rates rise by another 5 cents per kWh over the next decade, the array could help the facility save more than $500,000 annually. In addition, Dukes said, the system was built with an eye for future energy use.

“This system is good to go for a long time,” he said. As systems and products improve, the infrastructure is in place for the DOE to replace the panels with more efficient, more advanced modules. And the carport can be expanded. “They now have the infrastructure, and they can improve the system. It puts them in a good position long-term.”

However, the array will not power all of the DOE’s needs at Germantown.

“The system we’re provided will reduce the demand by 352 kW DC, and we are not putting energy back onto the grid. The facility will use all the electricity produced,” Dukes said.

He added that the facility has a 2.7 megawatt demand, but he would not disclose how much electricity the facility needed on an annual basis.

“Some of that must be classified,” he said.

Pictured: The Atlantic City Convention Center’s 2.36 MW array, installed by Pepco Energy Services, courtesy of the Center.