Large-scale electrical energy storage is becoming increasingly necessary due to the continued growth of intermittent renewable sources such as wind and solar. Reversible solid oxide cells (SOCs) have many desirable attributes for this application, but round trip efficiency is expected to be relatively low. Here we use thermodynamic calculations and gas chromatography measurements to demonstrate a reversible SOC storage chemistry where the fuel cycles between H 2O-CO 2-rich and CH 4-H 2-HCh gases, enabled by operating at reduced temperature and/or increased pressure. The CH 4-forming electrolysis reactions are less endothermic than the usual H 2- or CO-forming reactions, thereby allowing an improved round-trip efficiency. SOC requirements for this application are discussed.