The primary problem renewable energy systems must overcome is that electricity cannot always be produced in accordance with demand. This is a major drawback compared to the on-demand power production capability that fossil fuels offer. New technologies can only compete, if a constant power supply is permanently guaranteed. This constitutes a critical benchmark that renewable energy technologies must meet, if they are to replace fossil fuels. Reversible solid oxide cells (rSOCs) represent a promising approach to counteracting this issue. Here we show our developed rSOC plant which incorporates both the storage via electrolysis mode and the electricity production in the reverse, fuel cell mode. In order to achieve a high level of efficiency, the plant has been investigated and optimized with respect to internal waste heat recovery and compression. The final plant design shows an efficiency of up to 67.1% in fuel cell- and 76% in electrolysis mode and therefore a round trip efficiency of 51%.