EDF Energy has won a contract to supply renewable energy to 300 government departments and civil bodies.
The contract is worth £1 billion and will last for the next four years. It comes as part of the government's plan to convert all public sector offices to green power.
"This contract provides us with long-term relationships with many public sector clients, creating the right atmosphere for a collaborative approach to finding solutions to their energy requirements," an EDF spokesman said.
"The public sector is looking [at] . . . buying renewable energy, accelerating their efforts to reducing energy consumption and installing low-carbon electricity generation in government buildings."
EDF Energy, a French-owned company, took over London Energy in 1999. Its supplies for UK public offices will come from European and UK generators that have been accredited as "renewable sources" by energy regulator Ofgem.
The government will also be able to source energy directly from renewable sources such as wind turbines as part of the deal.
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