The Aegis-owned agency will handle communications planning for a campaign to raise awareness of the new initiative after pitching for the business.
Green Deal aims to help consumers implement energy-saving home improvements in order to make their homes more energy-efficient.
The agency will work on a consumer engagement plan designed to build trust and confidence in the policy.
The campaign will launch in mid-January.
Media buying will be handled by M4C, the Government’s dedicated media arm housed within Group M.
Jon Pile, the client director at Carat, said: "We will use our understanding of the sector to develop a strategy that frames the Green Deal around home improvement, an area that we know our key consumer segments are interested in."