Large gas engines will play a significant role in distributed power generation for the energy supply of the future. The lower amount of carbon in natural gas in comparison with other fossil fuels can be used to bridge the gap between a carbon-based and a carbon-free energy supply. The main objective of this paper is to provide an overview of the technological challenges the next generation of gas engines will face. Improvements in robustness and dynamic behavior will allow gas engines to meet the high transient requirements for the future power supply. The great fluctuations in gas quality anticipated with grid gas and liquefied natural gas impose high demands on both the transient behavior and the knock resistance of the engine. Technologies that enhance fuel flexibility by enabling sustainable power and heat generation using hydrogen-rich syngas from biomass and the efficient use of waste gases will be key. The most important technological components that maximize power output and efficiency as well as transient operation at very low emission levels are discussed. An advanced development methodology is applied in order to deal with the requirements presented by the technological challenges. The main future goals of gas engine development will be described by use of examples to illustrate the application of the methodology. In summary, the research and technological developments presented in this paper will support the transition from conventional to carbon-free fuel for reliable and sustainable power generation that meets future requirements for large gas engines. (C) 2017 Elsevier Ltd. All rights reserved.