On 20 June 2018, Claude Turmes was appointed Secretary of State for Sustainable Development and Infrastructures within the coalition government formed by the Democratic Party (DP), the Luxembourg Socialist Workers' Party (LSAP) and the Green Party (déi gréng), replacing Camille Gira who had passed away on 16 May 2018.
After the legislative elections of 14 October 2018, Claude Turmes was appointed Minister for Energy and Minister for Spatial Planning on 5 December 2018 in the coalition government formed by the DP, the LSAP and déi gréng.
Claude Turmes was a Member of the European Parliament from June 1999 to June 2018. He was the vice president of the parliamentary group of the Green Party in the European Parliament and was a member of the Committee on Environment, Health and Consumer Protection as well as a member of the Committee on Industry, Energy, Telecom and Research. He was the rapporteur of a large number of European directives, in particular on renewable energies, energy efficiency, the electricity market and climate plans, as well as on the European lobby register. From 2004 to 2018, he was the chairman of EUFORES (European Forum for Renewable Energy Sources), the Interparliamentary association for the promotion of renewable energies in Europe.