This review gives a worldwide overview on Power-to-Gas projects producing hydrogen or renewable substitute natural gas focusing projects in central Europe. It deepens and completes the content of previous reviews by including hitherto unreviewed projects and by combining project names with details such as plant location. It is based on data from 153 completed, recent and planned projects since 1988 which were evaluated with regards to plant allocation, installed power development, plant size, shares and amounts of hydrogen or substitute natural gas producing examinations and product utilization phases. Cost development for electrolysis and carbon dioxide methanation was analyzed and a projection until 2030 is given with an outlook to 2050. The results show substantial cost reductions for electrolysis as well as for methanation during the recent years and a further price decline to less than 500 euro per kilowatt electric power input for both technologies until 2050 is estimated if cost projection follows the current trend. Most of the projects examined are located in Germany, Denmark, the United States of America and Canada. Following an exponential global trend to increase installed power, today's Power-to-Gas applications are operated at about 39 megawatt. Hydrogen and substitute natural gas were investigated on equal terms concerning the number of projects. Display omitted •Electrolysis and methanation costs are estimated to fall by up to 75% under 500 €/kWel until 2050.•Most projects are located in Germany, Denmark, the United States and Canada.•95 Power-to-Gas projects with a combined load of 38.6 MWel are active in early 2019.•Exponential global increase in installed PtG-capacity is expected between 1993 and 2050.•The years 2012–2015 mark a breakthrough in average plant size and installed capacity.