Mayor Muriel Bowser did not provide financial details, but estimates that taxpayers in Washington will save $45m over the life of the accord.

The Department of General Services (DGS), which manages the District’s portfolio of government buildings, says South Chestnut will supply Washington with 125,000MWh of electricity each year – equivalent electricity for 12,000 homes.

“Directly sourcing renewable power costs 30% less than fossil fuel-based sources, reduces greenhouse gas emissions by 100,000 tons, and protects our city from volatile energy price increases,” says Mark Chambers, sustainability and energy management director at DGS.