Rouven Stubbe, consultant at Berlin Economics and energy expert at the Low Carbon Ukraine project delivered a speech at the European-Ukrainian Energy Day in Vienna on September 28, 2023. Subsequently, he participated in a panel discussion on “Energy security and building back better: Energy efficiency as part of energy security strategy and a tool for freeing resources for economic growth”. His remarks focussed on the opportunities and costs of a green reconstruction in the residential and district heat sectors. He demonstrated that a green reconstruction is possible and could bring numerous benefits. However, important obstacles need to be overcome first with ambitious policy reforms to mobilise required investments.