The renewable energy sector benefited when the Alliance '90/The Greens party joined the federal government between 1998 and 2005. Support for renewable energy continued under all following governments, regardless of composition, including the current CDU/CSU and SPD coalition government starting in 2018. The renewable energy sector was aided especially by the Renewable Energy Sources Act that promotes renewable energy mainly by stipulating feed-in tariffs and recently also market premiums that grid operators must pay for renewable energy fed into the power grid. People who produce renewable energy can sell their 'product' at fixed prices for a period of 20 or 15 years. This has created a surge in the production of renewable energy.