For a successful energy transition, Power-to-Gas (PtG) offers the opportunity to convert renewable electricity to substitute natural gas. This renewable synthetic natural gas (SNG) can be used for long-term storage, transport, or can be integrated into other energy sectors. Main challenges for the commercial application of PtG are to achieve a high PtG process efficiency, dynamic operation capability, and low investment and production costs. Within the STORE&GO project, three demo sites were developed, operated, and evaluated. An overall efficiency of > 75% is possible, the SNG production costs are expected to drop to less than 10 €-Cent kWh–1 in 2050.