The Department of Energy and Climate Change (DECC) is leading by example after having announced significant cuts to its carbon emissions.
An energy efficiency assessment of the body's Whitehall Place headquarters revealed it now has a Display Energy Certificate rating of C.
When the DECC first relocated to the building in 2008, it was rated G on the official A to G scale.
However, several improvements and renovations have seen the department cut its energy consumption by 60 per cent.
Minister of state for climate change Greg Barker said: "This is even more impressive when you consider that staff numbers in the building have risen since DECC took it on."
Estimations suggested the DECC saved around £156,000 in 2011/12, with even higher savings expected for 2012/13.
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