Walter is a Senior Advisor for European Energy issues, member of the Agency for the Cooperation of Energy Regulators (ACER) Board of Appeal, Chairman of Energy Regulators Regional Association (ERRA) Strategic Advisory Council as well as member of the Electric Power Research (EPRI) Advisory Council.

He is former Vice-Chair of the ACER Board of Regulators and Vice-President of the Council of European Energy Regulators (CEER). Walter headed the Austrian Regulatory Authority E-Control for 15 years. Furthermore he chaired the ACER and CEER Gas Working Groups for many years. In this period the Third Energy Package, the Security of Supply Regulation and the Energy Infrastructure Package were discussed, developed and implemented. Under his auspices the first and the second EU Gas Target Model were developed together with the involvement of market participants. Walter has worked on electricity and gas issues since more than twenty years and in management and consulting for more than thirty years.

Walter was the Chairman of the Supervisory Board of JSC MGU, the owner of the Ukrainian Gas Transmission System Operator GTSOU LLC during the implementation of the unbundling between 2018 and May 2020.