Article 27 2.

Member States shall ensure that gas and electricity transmission and distribution system operators apply the energy efficiency first principle, in accordance with Article 3 of this Directive, in their network planning, network development and investment decisions. National regulatory authorities or other designated national authorities shall verify that methodologies used by transmission system operators and distribution system operators assess alternatives in the cost-benefit analysis and take into account the wider benefits of energy efficiency solutions, demand-side flexibility and investment into assets that contribute to climate change mitigation. National regulatory authorities and other designated authorities shall also verify the implementation of the energy efficiency first principle by the transmission system operators or distribution system operators when approving, verifying or monitoring their projects and network development plans pursuant to Article 22 of Directive 2009/73/EC and to Article 32(3) and Article 51 of Directive (EU) 2019/944. National regulatory authorities may provide methodologies and guidance on how to assess alternatives in the cost-benefit analysis in close cooperation with the transmission system operators and distribution system operators, which can share key technical expertise.