Parliament’s scientific expert service says Germany’s planned clean heating rules may violate constitution

The German government’s draft law to decarbonise the heating sector may violate constitutional principles by postponing necessary emissions reduction efforts, a legal opinion drafted by the German parliament’s scientific expert service has found. The opinion commissioned by the Green Party said that the law might “unduly shift reduction burdens into the future” by abandoning a minimum renewable energy share of 65 percent for new heating systems and indefinitely allowing the installation of new oil and gas heating systems, the Frankfurter Allgemeine Zeitung reported. 

The new Building Modernisation Act, drafted by the coalition government of the conservative Christian Democrats (CDU) of chancellor Friedrich Merz and the Social Democrats (SPD), is meant to replace legislation passed under the previous government, which included the Green Party. During the 2025 election campaign, Merz and other leading conservative policymakers promised to “abolish” the earlier law.

In a landmark 2021 ruling, Germany’s Constitutional Court held that the government is obliged to spell out concrete steps to reduce emissions across all sectors and ensure costs and burdens are not shifted to later generations. The court ruled that emissions reduction overall cannot be scaled back but did not require every individual law to deliver greater reduction. However, the legal opinion suggested that the heating sector is too significant to the country’s overall emissions reduction trajectory to be treated as a routine law governing small aspects of climate action, the newspaper said. That means that alternative legislation should keep Germany on track to decarbonise its heating sector in line with the country’s 2045 climate neutrality target.  

“The parliament’s scientific expert service is not party-affiliated, which makes this opinion especially significant,” said Green Party energy policy expert Michael Kellner. The government parties “should take this very seriously and reconsider the plans,” Kellner argued. SPD energy expert Nina Scheer noted that the opinion had examined only the draft law and not the final version approved by cabinet. Given the so-called heating law’s long and controversial history in the past years and the urgency of achieving concrete decarbonisation progress fast, the government “cannot afford to adopt legislation with obvious constitutional flaws,” she added. 

A pro-climate action group within the CDU previously presented a separate legal opinion that also raised doubts about the Building Modernisation Act’s constitutionality. Several civil society organisations have since said they consider legal action against the government’s plan, which includes gradually replacing natural gas with bioenergy. Critics argue that the rollout of climate-friendly technologies and investments in decarbonisation will take significantly longer without a ban on new fossil boilers and that the households remaining on oil and gas likely face drastically higher costs and a possible decommissioning of gas networks in their areas.