The other innovation of the EU’s energy policy has been the emissions trading system (ETS), billed by the commission as “a cornerstone of policy to combat climate change”. Under the ETS, a cap is set by the EU on the total amount of greenhouse gases that can be emitted by the factories or power plants. The cap is reduced over time so that total emissions fall. In 2020, emissions from sectors covered by the EU ETS will be 21pc lower than in 2005.