The document discusses the need to model coupled energy networks to transition to a decarbonized future. It notes that historically energy systems like electricity and gas have been planned independently, but integrating them can reduce costs, increase efficiency, and lower emissions. It presents a software called SAInt that can model multiple energy systems simultaneously. Case studies show how SAInt can analyze issues like security of supply and optimize power-to-gas facilities. The document argues that coordinating different energy networks through modeling is crucial to achieving deep decarbonization goals across sectors.