TÜV SÜD has started to develop a guideline focusing on the hydrogen-readiness of combined cycle power plants in 2020, which serves as a basis for the third-party certification of concepts of original equipment manufacturers and engineering, procurement and construction companies as well as specific projects. The goal of the presentation is to give an overview of the latest developments and experiences made in the field. The first part is dedicated to gas turbine combined cycles. The latest certifications performed in this area are presented, namely the certifications of concepts based on specific gas turbines and heat recovery steam generators, as well as the first certification of a combined heat and power plant project in Germany. The scope of the guideline was extended to gas engine power plants at the be-ginning of 2023. This extension and the ongoing certifications of concepts and projects relative to gas engine power plants are described in the second part of the presentation. Discussing hydrogen-readiness for other existing infrastructure (e.g. pipelines) will be the last part of the presentation.