X-energy has expanded its planned Gaithersburg headquarters at Washingtonian Center, adding approximately 24,000 square feet to its footprint at 9801 Washingtonian Boulevard.
According to Maryland Newsletters, X-energy has taken another floor at the building, which has been rebranded as Waterfront at Washingtonian. The expansion brings the clean energy company’s total footprint to approximately 145,000 square feet in the nearly 315,000-square-foot building.
The additional space comes after X-energy’s lease was already among the area’s largest office deals of 2025. In July 2025, X-energy announced plans to consolidate its two Rockville offices into a new headquarters at Washingtonian Center. At the time, the company said the headquarters would encompass approximately 125,000 square feet.
X-energy, which specializes in nuclear reactor and fuel design technology, said the move would retain 260 full-time jobs in Montgomery County while creating more than 525 new positions over six years.
The company’s expansion has also helped fill space previously vacated by major tenants at 9801 Washingtonian Boulevard. According to Maryland Newsletters, the departures of Sodexo, which relocated to Pike & Rose, and Covance had left approximately half of the building vacant. Landlord Prime US REIT has since backfilled much of that space.
Montgomery County Economic Development Corporation worked with X-energy ahead of the company’s decision to remain and expand in Montgomery County, assisting with local incentive programs, property options, workforce resources and connections with local partners.
“We’re excited that X-energy is doubling down on Montgomery County,” County Executive Marc Elrich said when the headquarters project was announced last year. “This expansion is a win for our residents, bringing hundreds of good-paying jobs and strengthening our position as a center for innovation in clean energy and advanced technology.”
In addition to its growing Gaithersburg headquarters, X-energy announced plans for a 90,000-square-foot facility in Frederick dedicated to non-nuclear testing and prototyping of advanced reactor components.
X-energy was founded in Maryland and CEO J. Clay Sell said when the projects were announced that the company was entering “a period of unprecedented growth.”
